Engine Rebuilding Technical Guide, 11.2012

2012 NOVEMBER

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2 GM Gen IVThe key to cataloging GM’s popularGen IV engines is an understandingof the changes that GM made tothe Gen III engines to make themmore suitable for truck applica-tions, says Contributing EditorDoug Anderson. The 4.8L, 5.3L,6.0L and the 6.2L each came with anumber of variations over the yearsand now total nearly 30 differentmodels. Our detailed analysis offersinformation not available anywhereelse in the aftermarket.

12 CAT C7Caterpillar’s C7 common rail dieselengine has been used in applica-tions from Bluebird Buses toFreightliner Trucks. Diesel columnistand contributor Bob McDonald, inconjunction with Jasper Enginesand IPD, explores the differencesbetween early and late model C7s,and the opportunities that theseengines present.

Shortly after GM introduced theLS1 in the ’97 Corvette, they cre-ated a whole new family of small

block truck engines based on the LS1,including the 4.8L, 5.3L, 6.0L and the6.2L that each came with a number ofvariations over the years. In fact, GMbuilt nearly 30 different versions ofthese truck engines during the past tenyears. They all share a commonarchitecture and quite a fewcommon parts, but there aresignificant differences be-tween the Generation III (GenIII) and Generation IV (GenIV) engines along withplenty of variations fromyear to year. Just to put itall in perspective, therewere seven different5.3L engines in 2005 –along with the 4.8L and acouple of 6.0L motors.

Sorting them out hasbeen a challenge, but aftersix months of research alongwith a bunch of cores, sometake-out motors and a pile of newparts, we think we have figuredout most of the combinations andwhere they were used, but we mayhave missed something, so let us knowif you have some information to share.

The key to cataloging the Gen IVengines is an understanding of thechanges that GM made to the Gen IIIengines to make them more suitablefor truck applications. They neededmore torque, more power and betterfuel economy along with lower emis-sions, so they modified the block andseveral other components to accommo-date cylinder deactivation (they call itactive fuel management or AFM) andvariable valve timing (VVT). Here’s anoverview of the technology and what’sinvolved:

•AFM: The Gen IV blocks were castwith eight oil ports in the valley to ac-commodate the lifter oil managementassembly (LOMA) that deactivates thelifters for every second cylinder in thefiring order under light loads. The

knock sensors and cam sensor weremoved to make room for the LOMA,because it was bolted on top of the val-ley. A powerful new ECM was addedin ’07, so the crank reluctor wheel wasupgraded to 58 teeth and the cam gearhad four notches instead of one so thesensors

could provide more immediateand accurate information to the com-puter.

And, the special “De-Ac” collapsi-ble lifters were added for the fourcylinders that were going to be deacti-vated. This is amazing technology, be-cause the four cylinders aredeactivated in 45 milliseconds, in firingorder sequence, when the exhaustvalves are closed…at the same time theinjectors are turned off and the positionof the throttle blade is changed.

This process is reversed during reac-tivation except that the torque con-verter is momentarily unlocked toallow it to absorb the torque spike thatoccurs when the four cylinders comeback on line. That’s why AFM is onlyavailable with an automatic transmis-sion. AFM improves fuel economy upto 20% depending on the application,

because operating the engine on fourcylinders reduces pumping losses andincreases thermal efficiency.

As amazing as it is, AFM is notwithout problems that can affect en-gine builders. We’ll talk about noisylifters and oil consumption later.

• VVT: The use of variable valvetiming (VVT) required modifications tothe cams along with the timing compo-

nents and the front covers, but therewere no changes to the block itself,so we’ll note the differences whenwe discuss the individual compo-nents. Here’s how it works:

• Variable valve timing or“cam phasing” as it’s sometimescalled, “eliminates the compro-mise inherent in conventionalfixed valve timing and allowsa mix of low rpm torque overa broad range of enginespeed and free breathing,high-rev horsepower, whenneeded,” according to GM.

In other words, VVT lets theengine breathe better across the

full spectrum of rpm and loads,while creating a wide, smooth, power

band.The cam phaser can advance or re-

tard the cam by up to 62 crankshaft de-grees, depending on drivingrequirements. It’s advanced for asmoother idle and better low-endtorque, or retarded for more horse-power at higher rpm and better fueleconomy under light loads. VVT im-proves fuel economy when its used inconjunction with AFM because it helpsmaintain maximum torque when theengine is operating on four cylindersso the engine stays in the AFM modeas long as possible. And, it eliminatesthe need for an EGR system, becausecam overlap is used for internal EGRinstead of having an external EGRvalve along with the passages from theexhaust ports to the intake manifold.

Although all of the Gen IV enginescan accommodate both AFM and VVT,GM has used both of these technolo-gies selectively, depending on the en-

2 November 2012 | EngineBuilder

CONTRIBUTING EDITOR Doug Anderson PHOTOGRAPHY BY NS Photography [email protected]

gine and the application:• The 4.8L engines never came with

AFM and didn’t get VVT until 2010.• All of the 5.3L engines had AFM

from ’05 through ’11 with the followingexceptions:

• The LH8 and LH9 engines thatwere used in the small pickups and theH3 Hummer didn’t have AFM.

• The ’08-’09 LMF motor that wasused in the vans didn’t have AFM.

• All of the 5.3L engines got VVT in’10, but the LH9 and LMF engines stillcame without AFM in ’10 and ’11.

• The Gen IV 6.0L engines all gotVVT beginning in ’07, but the ’07-’09L76, the ’08-’09 LFA, and the ’10-’11LZ1 were the only ones that had bothAFM and VVT.

•All of the 6.2L engines came withVVT, but AFM was only used on the1st design L92 in ’07 and on the L94 in’10-’11.

Now that you have a better under-standing of what GM was trying to ac-complish when they upgraded the GenIV engines, it’s a lot easier to under-stand the changes that they made. Let’sbegin with the blocks by noting the dif-ferences between the Gen III and GenIV castings.

GEN III BlocksThe LS1 that was installed in the ’97Corvette was the first Gen III motor(the 265 was Gen I and the LT1 wasGen II). GM says it’s part of the smallblock family, but the only thing it hasin common with the earlier engines isthe bore spacing and the shape of thebell housing.

Soon after the car motors were in-troduced, GM replaced the old 305 and350 truck motors with the new 4.8L,5.3L and 6.0L engines that all used theLS architecture. There were both castiron and aluminum blocks used from’99 through ’08, but the cast iron blockswere usually found in 2WD pickupsand the aluminum blocks were used in

the 4WD pickups and SUVs along withthe Chevy SSR. They can all be identi-fied by the two knock sensors in thevalley and the cam sensor that’s lo-cated in the back of the block near thebell housing.

GEN IV BlocksThe first Gen IV truck engine was in-troduced in ’05 in the mid-sized SUVsincluding the Trailblazer and Envoyalong with some other models thatshared the same platform. The new5.3L came with AFM and an aluminumblock that incorporated severalchanges. The most noticeable differ-ence was the addition of the eight oilports in the valley that supplied oilfrom the LOMA tothe “De-Ac” lifters,so the two knocksensors weremoved from thevalley to the sidesof the block andthe cam sensorwas moved up tothe front cover inorder to makeroom for the oilports and the lifteroil management as-sembly.

The cast ironGen IV block forthe 4.8L/5.3Lshowed up in ’07,along with the castiron 6.0L that wasfollowed by an alu-minum version ofthe 6.0L in ’08.

The 4.8L/5.3Lcast iron block is a12576177, a12576178 or a12589779 casting.The aluminumblock is either a12571048, a 1260-

1900, a 12569513 or a 12568573 castingthat has three more bolt holes on thesides. Based on the cores we’ve seen,one or more of these holes are used forsome applications, so you can’t replacean aluminum block with an iron one,but you can replace an iron block withan aluminum casting. We suspect thatthe extra bolt holes on the aluminum5.3L blocks were used for a differentialsupport of some kind for the Trail-blazer/Envoy chassis, because the alu-minum block was the only one thatwas used in these small SUVs.

The 6.0L engines came with a castiron block that’s a 12576181 casting oran aluminum block that’s a 12568952casting. We don’t know if they’re inter-changeable because we haven’t seenthem side-by-side, but we suspect thatthey’re all the same because they wereboth used in the same trucks, vans andbig SUVs, and they were never in-stalled in the Trailblazer or Envoy chas-sis.

There’s also a FWD 5.3L block with


There are three front covers for the Gen IV engines including the FWD (left), RWD(center) and RWD with VVT (right). Note the location of the sensors and the extrahole for the VVT solenoid.

There’s one bolt hole on the rear cover for the FWD (right)that’s relieved to clear the smaller Buick bell housing.

The Gen IV motors came withthe chain guide in ’05 and’06, but they all got theblade-style tensioner begin-ning in ’07.

The cam gear was held onwith one big bolt beginningin ’07. If the engine had VVT,the bolt had an actuatorvalve in the center.

a 12569004 castingnumber on it. It’sunique, because ithas on the 231Buick bell housingand several differ-ent bolt bosses onboth sides that areused for the trans-verse FWD appli-cations.

Cranks andSensors

All of the Gen IV engines came with the same crank castingsthat were used in the Gen III motors, but there were a coupleof important differences.

• 4.8 L Gen IV ’07-’11 Trucks and VansAll of the 4.8L engines used the 12553482 casting with the

narrow (0.857˝) flange, but it had the 58X reluctor wheel(p/n 12586768) instead of the 24X reluctor wheel that wasfound on all the Gen III motors.

• 5.3L Gen IV ’05-’06 Trucks, Vans and SUVs These early Gen IV motors came with the 12552216 cast-

ing that had the 24X reluctor wheel, just like all the 5.3L GenIII motors, because they still used the early ECM.

• 5.3L Gen IV ’07-’11 Trucks, Vans and SUVsBeginning in ’07, all of the 5.3L truck engines came with

the 12552216 casting that had the 58X reluctor wheel, be-cause they all had the new ECM that needed more accurateinformation than they could provide with a 24X reluctorwheel.

• 5.3L Gen IV ’05-’07 (1st design) FWD CarsThe early FWD cars used the 12552216 casting, just like

the trucks, but it was 13.0mm, or about a half an inch,shorter according to GM, so the flange measures 0.750˝ in-stead of about 0.850˝ and the front snout is shorter, too. Thiscrank had the 24X reluctor wheel.

• 5.3L Gen IV (’07-’09 2nd design) FWD Cars

The late FWD cars used the shortened 12552216 castingwith the 58X reluctor wheel.

• 6.0L Gen IV ’07-’11 Trucks, Vans and SUVs The 6.0L engines all used the 12552216 casting with the

58X reluctor wheel. This is the same casting that’s used inthe 5.3L motors, but it’s balanced with a different bobweight, because of the heavier pistons. However, there aresome rebuilders who say they mix and match them and getaway with it.

RodsThere are long and short LS rods that came with and with-out pin bushings, but all of the Gen IV rods are bushed. It’seasy to tell them apart because the Gen III press-fit rods haverounded edges on one side of the beam and there’s no bush-ing.

• 4.8L: These engines all have the long rod that measuresabout 4.70˝ from bore-to-bore. They’re powdered metal witha cracked cap and no identification.

• 5.3L and 6.0L: All of these engines use the short, bushedrod that measures about 4.520˝ from bore-to-bore. They’re allpowdered metal and most of them have “GKN” and “3847”on the big end of the rod. Rebuilders need to be aware thatthe bushed rods weigh 30 grams more and the pin bore inthe press-fit rods is about .002˝ larger than the one for thebushed rods, so you can’t play mix and match if you’re shortof the bushed rods.

PistonsInstalling the right pistons in the right motor can be a chal-lenge, because there are flat tops and dished pistons thatcame with and without the valve reliefs that are required forthe engines that have variable valve timing (VVT), so it’seasy to make a mistake. Here’s our cheat sheet for the GenIV motors:

RingsThe rings for these engines are petty straightforward, be-cause there haven’t been many changes made since the ad-


The three bolt gear with a 1X sensor was replaced by the 1bolt gear or phaser that had a 4X sensor in ’07.

Note the difference in the shape of the teeth on the camgear. This asymmetrical design reduces chain noise.

The VVT motors have an electric sole-noid that modulates the oil to thephaser so it can advance or retard thecam.

Engine Year Piston GM P/N4.8L ’07- ’09 Flat Tops 89060486

’10-’11 Flat Tops with 2 reliefs 19208675

5.3L ’05-’09 Flat Tops 89060486’10- ’11 Flat Tops

with 2 reliefs 192086756.0L ’05-’09 LS2 Flat Tops 19178305

’07-’11 Dished 89017849(Ex Hybrids) w/2 reliefs’08-’09 LFA Flat Tops 19209286(Hybrid) w/2 reliefs’10-’11 LZ1 Flat Tops 19209286(Hybrid) w/ 2 reliefs

vent of the Gen III truck engines in ’99.• 4.8L: One set covers all the 4.8L

engines from ’99-’11. The rings are1.5mm/1.5mm/3.0mm.

• 5.3L: The same set covers all of the5.3L engines from ’99-’11, because thebore is the same as the 4.8L and therings are still 1.5mm/1.5mm/3.0mm.

• 6.0L: There have been two ringsets for the 6.0L from ’99-’11.

• The rings in the first set that fitsfrom ’99-’04 are1.5mm/1.5mm/3.0mm.

• The rings in the second set thatfits from ’05-’11 are1.2mm/1.5mm/2.5mm.

Be sure to match the pistons andrings for each application.

Oil PumpsThe Gen IV engines have used two dif-ferent oil pumps that have three differ-ent springs for the relief valve.

• The 12586665 pump that was car-ried over from the Gen III applicationspumped 0.96 cubic inches per revolu-tion. It was used on all the cast ironGen IV motors and on a few of the alu-

minum ones like the LS2 and LH8 thatcame without AFM or VVT. The re-placement pump is the Melling M295.

• GM introduced a new pump be-ginning in ’05 with 33% more capacitythat pumped 1.26 cubic inches per rev-olution. There were two versions ofthis pump, but the only difference be-tween them was the spring for the re-lief valve. The original 12571885 pumpthat was used for a couple of applica-tions in ’05-’07 had a red spring that re-lieved the oil pressure at 43 lbs.

Based on our research, we believethat GM originally intended to buildthese early 5.3L Gen IV engines withboth AFM and VVT, so they increasedthe pressure and the volume to makesure the pump could supply enoughoil for both of them, but they appar-ently decided they didn’t need thehigher oil pressure because this pumpwas replaced by the 12612289 that hada 33 lbs. relief valve in ’08. The originalhigh-pressure pump is available fromMelling as the M355, but we prefer touse the M365 that has the lower pres-sure instead.

• The 12612289 is the latest versionof the big pump. It has the bigger hous-ing with the extra capacity, but it hasthe yellow spring that reduces themaximum oil pressure from 43 lbs.down to 33 lbs. It’s used on all of thetruck engines with an aluminum blockthat have AFM or VVT or both. It’s theMelling M365.

• The LFA and LZ1 Hybrids camewith a variable displacement oil pumpthat supposedly saves two horsepower.It’s available under p/n 12625823 forthe LFA and p/n 12623423 for the LZ1.

We recommend replacing all thefactory oil pumps with aftermarketpumps because the original design hasseveral flaws that can lead to problems.

• The clearance between the rotorand the backing plate is so tight (.000˝to .003˝) that most of the covers arebadly scored by the time we see them.In fact, GM is having problems withthem scoring and seizing while they’restill under warranty.

• The thin steel backing platewarps, leaks, and bleeds off oil pres-sure constantly.

• The OEM relief spring starts by-passing oil at 6#, which aggravates theproblem if the engine has low oil pres-sure at hot idle, and the constant fluc-tuation of the relief valve tends to wearthe bore in the aluminum housing sothe oil bypasses the relief valve and theengine has low oil pressure.

The replacement pumps address allof these problems, so we suggest usingnew ones instead of trying to rebuildthe OEM pumps. The chart on page 10explains the application by RPO andVIN code. You will note that we super-


The Gen IV engines without AFM had aflat cover (left) that sealed off the valleyand the oil ports. The lifter oil manage-ment assembly (right) was used on theengines with AFM.

The perimeter gasket on the left is usedfor the cover without AFM and the oneon the right is used for the one withAFM.

There are four solenoids on the lifter oil management assembly that are connectedto the eight oil ports that control the “De-Ac” lifters.

The shield that fits over the AFM reliefvalve in the pan deflects the oil downand away from the crank so it doesn’tend up on the walls.

seded the 43 lbs.12571885 with

the 33 lbs. 12612289, but you can runthe 43 lbs. pump on the ’05-’07 LH6and LS4 engines if you prefer.

Timing ComponentsThere have been several changes madeto the timing components over theyears. This can create a problem for re-builders, because the chains, gears andtensioners are not interchangeable eventhough they may fit several differentapplications. Here are the correct gearand sensor combinations:

• All of the Gen III motors had thecam sensor located on the back of thecam so they used a “plain” gear withlots of holes in it that was bolted to thefront of the cam with three small cap-screws.

Note: GM and most vendors haveconsolidated their timing gears/sets byreplacing the “plain” gear with the ’05-’06 Gen IV gear that has a single notchin it and three capscrews. It works fine.

• The cam sensor was moved to thecam gear and front cover in ’05 in orderto make room for the oil ports thatwere required for AFM. The cam gearhad a single notch (1X) on it through’06, because these engines still used the

old ECM, and itwas bolted tothe cam withthree small cap-screws, just likethe Gen III mo-tors.

• When GMswitched to the

new ECM in ’07, they changed the camgear on the 4.8L and 5.3L. It was heldon with one large bolt and it had fournotches (4X) on it so it could provide amore accurate signal to the computer. Italso provided a backup signal andlimp-home capability in case the cranksensor failed. This gear was used upthrough ’09 on all of these engines, be-cause none of them had VVT and thephaser with the 4X sensor attached toit.

• The cam gear on the 6.0L engineswas changed in ’07, too, but all of theseengines came with VVT, so the camgear was an integral part of the camphaser assembly that had a stamped-steel plate with four notches (4X) at-tached to the front of it. This sameassembly was used on all the 4.8L and5.3L motors when they got VVT in2010.

Here’s a recap of the cam gears andsensors for the Gen IV motors:

4.8L ’07-’09 4X One Bolt’10-’11 4X Phaser P/N 12606358

5.3L ’05-’06 (LH6) 1X 3 Bolts’07-’09 4X One Bolt’10-’11 4X Phaser P/N 12606358

6.0L ’05-’06 (LS2) 1X 3 Bolts’07-’09 (LS2) 4X One Bolt’07-’11 (ex. LS2 and Hybrids) 4X Phaser P/N 12606358’08-‘11 (LFA & LZ1 Hybrids) 4X Phaser P/N 12602699

TensionersGM has used either a chain damper ora tensioner on all the GEN IV engines,depending on the application. Theyboth fit all the Gen IV blocks, butthey’re not interchangeable.

• The 12588670 is the wedge shapedguide that was used on the ’05-’06 LH6and the LS2 along with ’05-’07 1st de-sign LS4, because they all had 1X camgear with the three bolt cam.

• The 12585997 is a blade style,spring- loaded tensioner that was usedfor all ’07 and up Gen IV motors that

had the 58X crank reluc-tor wheel and the 4Xcam gear or the phaser.This tensioner must beused on all of these en-gines because GM cre-ated some initial slackin the chain by modify-

ing the tooth profile so the chain satdeeper in the gear, but that created anoise problem, so the powdered metalgears have an asymmetrical pattern onthe teeth that reduces the noise byeliminating the common harmonic fre-quency. Look at the picture of the 4X


The oil pump forthe aluminum en-gines with AFMand/or VVT had33% more volume.Note the differ-ence in the widthof the gerotor onthe right.

The miniature AFM lifter has twospring-loaded pins that ride up ona ledge inside the roller bodyuntil they are depressed by theoil pressure that deactivates thelifter and allows it to drop downinside the roller body.

The intake rockers had to be offset by6.0mm to clear the large, rectangularports on the 823/ 5364 heads that wereinstalled on the 6.0L Gen IV engines be-ginning in ’07.

Most of the 6.0L Gen IV engines camewith either flat top or dished pistonsthat had valve reliefs for VVT, but theones for the LS2 didn’t have reliefs be-cause it didn’t have VVT.

The cam for the ’05-’06 Gen IV engineshad three bolts for the cam gear, the’07-’09 engines without VVT had a sin-gle bolt and the all of the engines withVVT had the single bolt along with thetwo “ears” that supplied oil to thephaser.

The second journal was grooved andhad a hole that fed oil into the hollowcore for the engines with VVT.

gear that’s on page 5 and you will seethat the teeth aren’t symmetrical be-cause they all vary in size and width.

The bottom line is that you mustuse the correct chain/gear/tensionercombination for each application oryou will have a noisy timing set thatwill fail prematurely.

CamshaftsGetting the right cam in each particularengine can be a challenge, becausethere have been 12 different cams usedin the Gen IV motors and they’re notusually interchangeable becausethey’re varied, unique and specific toeach application in most cases. Thereare two different bolt patterns for thecam gear and some had AFM or VVT,or both or neither. Here’s what youneed to know:

• You have to use the three bolt camin the ’05-’06 Gen IV 5.3L motors inorder to use the 1X cam gear.

• Youmust use anAFM cam inthe AFM mo-tors, becausethe ramps onthe AFMcylinders arelonger sothey can takeup the lock-ing lash that

exists betweenthe ledge inthe outerbody and thetwo pins inthe lifter whenthe cam is onbase circle.

• All of theVVT cams are

drilled back to the second journal that’sgrooved and there’s a hole in it thatfeeds oil into the hollow core so the ac-tuator valve can regulate the positionof the cam phaser by applying oil intoeither side of the phaser through thetwo “ears” in the front of the cam. Youcan use a cam that’s machined for VVTin a non-VVT motor, because the largebolt for the gear will plug the hole andblock off the oil, but you must have aVVT cam with the groove and the earsin order to make the VVT work. GMhas chosen to machine all their latecams for VVT whether the engine hasit or not, so it can be confusing, but justremember that you can’t use a singlebolt cam without the groove and thetwo ears in a VVT motor.

• We have combined a few applica-tions when GM has superseded themand we hope to consolidate a few morebecause the specs appear to be pretty

close, but we’re concerned about howthe computer will react to any changesso we’re sneaking up on it.

• The last four digits of the OEMpart number are always etched on theback of the rear journal, so it’s easy toidentify the cam unless it’s a super-seded number, and there are a coupleof them, so that makes it more difficult.The good news is that we have figuredout the complete part numbers for thesuperseded cams and included themon the chart on page 10.

LiftersHere’s where the fun starts.

• GM changed the location of the oilhole on the Gen IV lifters that are usedin the cylinders that aren’t deactivatedon the AFM motors. The oil hole is onthe same side as the flat instead of 90°away from the flat. We’re told that ithas to do with limiting the amount ofoil that can leak out of the lifter whenthe engine is shut off and that thischange helps eliminate noisy lifters atstart-up, so rebuilders should probablyuse the correct lifters for the Gen IV en-gines, even though they cost more.

• There are three different “De-Ac”lifters. The early ones were made by ei-ther Eaton or Delphi. The latest one,that’s made exclusively by Delphi (wecall it the “Delphi II”), was designed to


The lifter guides for the AFM engineshave one notch that indexes on a tab inthe block to ensure that it’s installed inthe right location. The ones for the en-gines without AFM have two notchesbecause the lifters are all the same sothey can fit in any location.

The original Delphi “De-Ac” lifter is onthe left and the Eaton with the three“windows” is on the right. Neither oneshould be reused. Unfortunately, youcan’t tell the difference between a Del-phi I and Delphi II externally.

The early “De-Ac”lifters have a smallhole in both the bodyand the plunger. Thelatest version- the“Delphi II” -has sev-eral large holes thatrefill the lifter immedi-ately and eliminatelifter noise at start-up.

The Gen III, oval port heads (bottom)were replaced by the ones with “Dee”shaped exhaust ports and biggervalves on all the 4.8L/5.3L Gen IV mo-tors.

Notice the difference in the size of theholes for the lifters and the location ofthe notches in each lifter guide.

eliminate the problem GM had withnoisy lifters at start-up with both of theearly designs. If you take a “De-Ac”lifter apart, you will see why there’s aproblem, because there’s a completeminiature lifter assembly inside theouter roller body where the plungerused to be, so there’s not enough oil inthe downsized upper chamber to refillthe lower chamber after the engine hasbeen shut off long enough to let thelifter leak down. GM couldn’t changethe physical size of the lifter to fix thisproblem because it had to fit inside theroller body, so they reduced the leakdown rate of the lifter and opened upthe oil holes in both the lifter and theplunger to make sure they could refillthe upper and lower chambers imme-diately after start-up. These changeseliminated the problem they had withnoisy lifters, so we recommend in-stalling all new “Delphi II De-Ac”lifters in every AFM engine. Its notworth taking a chance on the originalEaton or Delphi lifters if you have toreplace them under warranty when theengine gets 30,000 or 40,000 miles on it.The “Delphi II” lifters are availablefrom GM for about $50 apiece or for alittle less from at least one supplier inthe aftermarket. Be sure to specify thelatest “Delphi II” lifters when youorder new ones wherever you getthem. The correct GM part number is12639516, according to our Chevydealer.

Lifter GuidesThere have been three different lifterguides used for the Gen IV enginesand they’re unique to each applicationso they’re not interchangeable.

All the engines without AFM have auniversal guide that accommodates

four regular lifters and fits in any loca-tion because it has two notches on theguide that match any of the locatortabs on the block. It has the part num-ber, 12595365, molded right on it.

The AFM engines have two differ-ent lifter guides that have two big holesfor the “De-Ac” lifters and two smallholes for regular lifters. The 12571596 isfor the front cylinders on both sidesand the 12571608 is for the back twocylinders on both sides. GM designedthem so you can’t physically inter-change them because they each have asingle notch that fits over the singleraised tab in the block which locatesthe guide and the lifters correctly.

HeadsThere have been several different headcastings used on the Gen III and Gen1V motors. The intake and exhaustports have been changed along withthe valve sizes and springs. The charton page 46 lists all the truck heads wehave seen by year, RPO and VIN code,including the ones for the Gen III mo-tors, and describes each one by partnumber, casting number, port configu-ration and valve size. Once you seethem all together, the patterns becomemore obvious.

Head GasketsGM made a slight modification to thecoolant passages in the head gasketsthat were used on the 799/12564243

heads with “Dee” shaped exhaustports, so be sure to use the latest designon the Gen III L33/VIN B and all of the4.8L/5.3L Gen IV engines that camewith these heads.

SpringsGM has used two different valvesprings for the truck engines.

• The original spring that was usedon the trucks from ’99 through ’04 hadless tension than the later one. The ac-tual specifications will vary dependingon the checking height specified by thevendor, but we have found that 75 lbsat 1.800˝ and 180 lbs. at 1.420˝ are ac-ceptable numbers for our use.

• GM introduced a new, strongerspring in’05 that was designed to ex-tend the operating range of the enginea little bit higher because the newheads had bigger valves and betterports that flowed more air. We checkthem at 85 lbs. at 1.800˝ and 245 lbs. at1.320˝.

Rocker Arms and Supports• All of the Gen III and Gen IV 4.8Land 5.3L motors came with straight in-take and exhaust rockers along with allthe Gen III 6.0L engines and the Gen IVLS2 that was used in some trucks. Theywere bolted to a rocker support thatwas mounted on the square pedestalsthat were machined on the heads.

• When GM installed the823/5343 heads on the Gen IV 6.0Lengine in ’07, they had to offset theintake rockers by 6.0mm so thepushrods would clear the big, rectan-gular intake ports found on thesecastings. The rocker support (p/n12569167) was modified to fit the


The 6.0L Gen IV motors got the823/5364 castings with the big rectan-gular intake ports instead of the oneswith the smaller cathedral ports thatwere used on all the rest of the Gen IVengines.

The 24X crank sensor wheel (left) wasreplaced by the 58X on all Gen IV mo-tors beginning in ’07.

The chamber for the rectangular portheads (left) was modified to incorpo-rate two quench areas and biggervalves.

The rectangular port heads (left) haveround bolt pads instead of the squareones, so there are two different rockersupports.

round pedestals that were machinedon these heads.

PushrodsThe Gen IV engines use the samepushrods that were used for all theGen III engines.

The LOMA and Valley CoversThe “lifter oil management assem-bly”(LOMA) that contains the sole-noids that control the “De-Ac” lifterscovers up the valley on the engineswith AFM. The early ones were boltedtogether as an assembly, but the laterones are riveted so they can’t be disas-sembled. GM offers a perimeter gasket(p/n 89017690) to service the LOMA,but that means you have to cut the gas-ket and reuse the existing inner portionthat seals the oil ports and that’s prettysuspect based on the limited number ofsamples we’ve seen on cores. The onlyalternative is to install a new LOMA as-

sembly or tell the installer that he hasto put a new one on in order to validatethe warranty. They cost about $200apiece, but it may be money well spentif it avoids a problem with the AFMlifters, because you will be blamedeven though it’s not your fault.

If the engine comes without AFM,there’s a plain cover (c/n 12598833)and a perimeter gasket (p/n 12610141)plus eight “O” rings that seal off thevalley and the oil ports. There’s no pro-vision for the PCV used on the trucks,but some of the cars use one that has aPCV baffle, so be sure to use the rightone for the application.

Front CoversThe Gen IV motors have used threedifferent front covers, two for thetrucks and one for the cars.

• All the Gen IV truck engines, ex-cept those with VVT, use a 12600326casting with a hole for the cam sensorthat’s offset toward the driver’s side.

• The Gen IV motor with VVT stillhas the hole for the cam sensor offset tothe driver’s side, but it also has a largehole in the center for the solenoid thatregulates the oil pressure for the camphaser. Our sample has a 12594939casting number which is the same asthe OEM part number.

• The FWD cars have a unique frontcover that has the hole for the cam sen-sor offset to the passenger side. Wehave seen two different versions, butthe latest one (p/n 12611880) super-sedes the earlier 12580288 casting, sothey appear to be interchangeable. Thelater one has an unusual casting num-ber that’s “CDCG/A,” whatever thatmeans.

Rear CoversThese engines have two different rearcovers.

• The RWD trucks (and cars) haveeither a 12556105, a 12587100, a12598301 or a 12572014 casting. Theyare all very similar to the Gen III rearcover (c/n 12559287) and appear to beinterchangeable.

• The FWD cars use the 12587100casting. It’s similar to the RWD cover,but it was modified to provide more

The Gen IV aluminum blocks have oneextra bolt hole on the passenger side.

The Gen IV aluminum blocks have twoextra bolt holes on the driver’s side.

LITERS YEAR RPO VIN BLOCK OIL PUMP AFM VVT CRANK CAM SENSOR CAM P/N MAT'L SENSOR4.8L 2007-09 LY2 C CI M295 58X 4X GEAR/1-BOLT 12593205 - 126254374.8L 2010-11 L20 A CI M295 58X 4X GEAR/1-BOLT 126254375.3L 2005-06 LH6 M AL M365 ° 24X 1X GEAR/3-BOLT 125695255.3L 2007-09 LH6 M AL M365 ° 58X 4X GEAR/1-BOLT 12593207 - 126254365.3L 2007-09 LY5 J CI M295 ° 58X 4X GEAR/1-BOLT 12593207 - 126254365.3L 2007-09 LMG O CI M295 ° 58X 4X GEAR/1-BOLT 12593207 - 126254365.3L 2007-09 LC9 3 AL M365 ° 58X 4X GEAR/1-BOLT 12593207 - 126254365.3L 2008-09 LMF 4 CI M295 58X 4X GEAR/1-BOLT 126254375.3L 2008-09 LH8 L AL M295 58X 4X GEAR/1-BOLT 126254375.3L 2010-11 LH9 P AL M365 ° 58X 4X PHASER 126254375.3L 2010-11 LMF 4 CI M295 ° 58X 4X PHASER 126254375.3L 2010-11 LMG 0 CI M295 ° ° 58X 4X PHASER 126254365.3L 2010-11 LC9 3 AL M365 ° ° 58X 4X PHASER 126254366.0L 2005-06 LS2 H AL M295 24X 1X GEAR/3-BOLT 125745196.0L 2007-08 LS2 H AL M295 58X 4X GEAR/1-BOLT 125932066.0L 2007-09 LY6 K CI M295 ° 58X 4X PHASER 12612274 - 126254396.0L 2007-09 L76 Y AL M365 ° ° 58X 4X PHASER 12629698/ 12625438 (09)6.0L 2008-09 LFA 5 AL VARIABLE ° ° 58X 4X PHASER 126296986.0L 2010-11 LZ1 J AL VARIABLE ° ° 58X 4X PHASER 126296986.0L 2010- LY6 K CI M295 ° 58X 4X PHASER 126254396.0L 2010-11 L96 G CI M295 ° 58X 4X PHASER 12625439/ 12625440 (11)

CHEVY GM IV Engines Chart


clearance around one of the bolt bossesfor the smaller FWD bell housing.

Problems With The LS MotorThere are a couple of problems with theGen IV motors that may affect how yourebuild the AFM motors, especially theones with aluminum blocks.

• Lifter noiseafter a two-hourshutdown can bean issue with theengines that have

AFM. If the tickinglasts more than 10seconds afterstartup and it’s diag-

nosed as lifter noise, GM is replacing thelifters with the latest “Delphi II” lifters(p/n 12639516) that we described earlier.We recommend using all new “Delphi II”“De-Ac” lifters in these engines to avoidthe possibility of a warranty 30,000 or40,000 miles later, because you have to re-move the heads in order to replace the

lifters, and that gets really expensive!• Some of the aluminum engines with

AFM have experienced oil consumption,too. GM says that the oil spray that is dis-charged from the AFM pressure reliefvalve in the crankcase may result in car-bon deposits in the ring grooves that stickthe rings and cause oil consumption.They have modified the rocker cover tochange the calibration for the PCV forsome applications, but the real fix is theinstallation of a shield (p/n 12639759)over the AFM relief valve to deflect the oildown into the pan instead of allowing itto hit the crank that throws it up on thecylinder walls. Rebuilders should includethis shield with the LC9, L76, L96, LS4,LFA and LZ1 along with a picture and in-structions so the installer knows where itgoes and why it must be installed beforeputting the pan on the engine.

• The cam phaser hasn’t created anyproblems for GM, but it probably shouldbe replaced when the engine is rebuilt fora couple of reasons. The cam gear is apart of the phaser, so if the gear is worn,the phaser will have to be replaced. Thereare some internal parts that wear, too,and there’s no easy way to get the phaserapart to inspect them. So, the only real al-ternative is to try to clean it and pressuretest it to see if it’s okay – or replace itevery time to make sure it will go the dis-tance without a comeback. By the way,there are two different phasers. The onefor the LFA and LZ1 Hybrids is a p/n12602699, and the one for all the rest ofthe VVT applications is p/n 12606358.

ConclusionThat’s pretty much the story about theGen IV engines. It’s interesting to seehow GM has taken a building-blockapproach to this family that has al-lowed them to mix and match a vari-ety of castings and components tocreate 28 engines that are all tailored todifferent needs and applications.

Unfortunately, that means there are28 different truck engines that we allneed to rebuild, so it’s going to be realcomplicated for everyone in the indus-try, but it can be done if we identifyeach RPO and rebuild it exactly theway GM built it in the first place.Hopefully this information will makeit easier for everyone to do that, but themoral of the LS story is, “Don’t guess


The Gen IV blocks have 8 oil ports in the valley for AFM in-stead of the two knock sensors that were located in the val-ley on the Gen III motors.

4.8L 4.8L/GEN-III RPO VIN GM PN CN VALVES PORTS 99-07 LR4 V 12578925 12559862 I 1.890” Cathedral 12561706 E 1.55” Oval

4.8L 4.8L/ GEN-IV RPO VIN GM PN CN VALVES PORTS 07-09 LY2 C 12629049 799 I 2.00” Cathedral 10-11 L20 A 12564243 E 1.55” “Dee”

5.3L 5.3L/GEN-III RPO VIN GM PN CN VALVES PORTS 99-07 LM7 T 12578925 12559862 I 1.890” Cathedral 02-07 L59 Z 12561706 E 1.55” Oval 03-04 LM4 P 5.3L/GEN-III 05-07 L33 B 12629049 799 I 2.00” Cathedral 12564243 E 1.55 “Dee”

5.3L 5.3L/GEN-IV RPO VIN GM PN CN VALVES PORTS 05-09 LH6 M 12629049 799 I 2.00” Cathedral 07-09 LY5 J 12564243 E 1.55” “Dee” 07-11 LC9 3 07-11 LMG 0 08-11 LMF 4 08-09 LH8 L 10-11 LH9 P 05-09 LS4 C

6.0L 6.0L/GEN-III RPO VIN GM PN CN VALVES PORTS 99-00 LQ4 U 12568175 12567173 I 2.00” Cathedral CAST IRON E 1.55” Oval 01-08 LQ4 U 12562319 12562317 I 2.00” Cathedral 02-07 LQ9 N E 1.55” “Dee” ALUMINUM

6.0L 6.0L/GEN-IV RPO VIN GM PN CN VALVES PORTS 05-09 LS2 H 12564243 I 2.00” Cathedral E 1.55” “Dee” 07-10 LY6 K 12629051 823 I 2.165” Rectangular 07-09 L76 Y 5364 E 1.590” “Big Dee” 08-09 LFA 5 12629051 823 I 2.00” Rectangular 10-11 LZ1 J 5364 E 1.55” “Big Dee” 10-12 L96 G 12629051 823 I 2.165” Rectangular 11 LC8 ? 5364 E 1.590” “Big Dee”

6.2L 6.2L/GEN-IV RPO VIN GM PN CN VALVES PORTS 07-08 L92 8 12629091 823 I 2.165” Rectangular 09-11 L9H 2 5364 E 1.590” “Big Dee” 10-11 L94 F

GEN III AND GEN IV LS TRUCK HEADS

Even in today’s struggling econ-omy, there are still creativeways to make an income, and

the same is true with the transporta-tion industry. I am sure there areplenty of automotive and diesel en-gine shops finding new areas inwhich to direct their expertise.

I believe society naturally directsthe outcome of its environment: ifsomeone manages a quality inde-pendent automotive repair shop,they will always be looking forways to increase their educa-tion and specialty tools astechnology changes. In orderto take care of their cus-tomers when the warrantyruns out and they nolonger visit the dealer-ship, shops need toadapt. A quality inde-pendent automotive re-pair facility that keepsup with technologicaladvances is no differentthan any other competitiveindustry. Look at the automo-tive manufacturers themselves.Today’s society has directed themto make more power, use less fueland offer more features.

The same can be said about theheavy-duty industry as well. Heavy-duty diesels that transport goodsacross the country along with theones that are used to excavate high-ways are all using the same competi-tive strategies to stay on top. Inaddition, the EPA has raised stan-dards and lowered emissions in re-sponse to or as a cause oftechnological advances.

The Caterpillar C7 engine is noexception. Another popular Cat en-gine, they’re now seeing rebuildingopportunities, so we thought wewould take a look at how thingshave changed to get to where we aretoday.

This popular engine was releasedin 2003, and now has a total produc-tion of over 300,000 units. With a

range from 190hp to 360hp, this mid-range six cylinder engine is very ver-satile. It can often be found inon-highway trucks, and also in off-highway applications such as load-ers, skidders, excavators, motorgraders, and industrial and marineunits. It is actually a7.2 liter

(439 cu. in.)engine with a4.33” bore (110mm)and 5.0” stroke(127mm).

From 2003 to 2009, the C7 wasCaterpillar’s primary engine formedium-duty trucks with a GVWRof 18,000 to 33,000 lbs. from GMC,Ford, Freightliner and Paccar. TheCat C7 is an inline 6-cylinder dieselengine with a displacement of 7.2liters or 441 cubic inches. At the endof its production cycle, the engine in-cluded a number of features includ-ing turbocharging, common rail fuelinjection system, full electronic con-trol system and Caterpillar’s ACERTfuel/air management system. Tomeet regulations, advanced emissionsolutions include a closed crankcasebreather and a diesel particulate fil-ter using Cat’s proprietary regenera-

tion system. Of course, to understand where

we are, it’s often necessary to take alook back. The C7 was Caterpillar’sanswer to growing demands foremissions reductions and was de-rived from its older engine brother,the Cat 3126.

The 3126 was, in fact, the re-placement for the Cat 3116

and that’s where this storyREALLY starts. The 3116engine was used up untilthe mid ’90s until society

demanded more. The3116 caused strong reac-tions in many people,to say the least. Not too

many 3116 owners wereproud of Cat’s reputationbehind the engine and,while the engine didprove reliable, it didn’toffer enough power formost users and was notvery fuel-efficient.

To counter its poorreputation and meet

tightening emissions de-mands, Cat released the

3126 in 1997 as its firstmidrange electronic diesel en-

gine. The 3126 could be found inGMC, Ford and Freightliner trucks,Thomas and other school buses,recreational vehicles and smalleremergency vehicles. It was also of-fered in off-road applications as wellin excavators, skidders, motorgraders, industrial, and marine. De-pending on application, the 3126ranged from 175 to 300 hp. It was apart of the “gear fast, run slow”strategy from Cat, which allows theengine to run slower at cruisespeeds, translating into potential re-duced fuel consumption. The 300horsepower version produced peakpower at 2,200 rpm with the torquepeaking at 800 ft.lbs. at 1440 rpm.

To achieve its electronic advance-ment the 3126 engine utilized HEUI(Hydraulic Electronic Unit Injector).


CONTRIBUTOR Robert [email protected]

All HEUI designs work in the samefashion. The components include anECU (Electronic Control Unit), elec-tronic injectors, and various sensorsplaced on the engine and vehicle.This same technology is also foundin the Ford Power Stroke and wasused by International in several dif-ferent applications with their inlinesix-cylinder engines in the DT seriestrucks, but HEUI is a trademark ofCaterpillar.

Caterpillar used high-pressure oilto make even higher injection pres-sures, effectively squeezing fuel outof the injector nozzle. In a HEUI sys-tem, the oil pump inside the enginesupplies oil to a high-pressure oilpump or HPOP. The HPOP is gear-driven by the engine and sends pres-surized oil to a galley in the cylinderhead that surrounds the injector.

When the ECU commands the injec-tor to open, the high-pressure oil en-ters the injector and pushes down onan intensifier piston inside the injec-tor body which in turn pushes downon a plunger.

The intensifier piston is generallyseven times greater in size than theplunger. At idle, the HPOP suppliesapproximately 500 psi of pressure tothe injector. Caterpillar used highpressure oil to squeeze fuel out of theinjector nozzle. The injector has twocompartments in the lower portionof the injectors body. One for highpressure oil to enter the injector andthe other is to store incoming fuelwhich is provided by a pump at 80psi. When the injector is commandedto open, the 500 psi oil enters andthen sends fuel out of the tip at 3,500psi (7 x 500 because of the intensifier

piston). At wide open throttle, theHPOP can supply the injector withup to 3,000 psi of oil pressure. So, thefuel being ejected from the injectortip can reach as high as 21,000 psi.

The volume of oil that is suppliedby the HPOP is controlled by an elec-tronic regulator. The various sensorsmonitor HPOP pressure in relation toengine parameters from coolant tem-perature, oil temperature, cam posi-tion sensor, throttle position,manifold pressure, and barometricpressure. Utilizing these electroniccontrols along with high-pressure oilbrought about more precise enginecontrol as well as more economy.This engine design also increasedpower and reduced emissions.

One thing that really set the 3126apart was the design of its cylinderhead. The inline-six cylinder head in-


This chart provides engine and market information on 17 different configurations of Caterpillar C-series engines, from theC7 to the C280-16 model. Chart courtesy of IPD LLC.

corporated three valves per cylinder:one exhaust valve and two intakevalves. The head was named “cross-flow” and revolutionized the airflowof the engine. Incoming air enteredthe engine from the right hand sidethrough the intake valves and exitedthrough the exhaust valve on the lefthand side. This cross-flow designchanged the swirl characteristics ofthe cylinder head and was a big fac-tor in improving power and combus-tion on this diesel engine. With all ofthese changes in the 3126, the powerwas almost double that of the 3116.

In 1998, after one year, Caterpillarreleased the 3126B, basically thesame engine configuration with im-proved electronics. The ECU was up-graded from a 40 pin to a 70 pinconnection. This advanced ECU wasused to gain more engine control, asCaterpillar sought less smoke evenupon cold start as emissions de-mands increased. Another concernwas to lower the operating decibelsof the engine. The previous 3126 wasconsidered to be “too loud,” so bycontrolling the engine with advancedelectronics, fuel delivery strategies

were also changed, lowering thedecibels and making the engine moreefficient.

As emissions tightened even fur-ther, Caterpillar released the 3126E in2002. The 3126E was the same engineplatform with even more advancedelectronics and redesigned HPOP.The HPOP gave higher injectionpressures and a new leak-free de-sign. If the HPOP did leak, it wouldleak into the engine, unlike older de-signs that tended to leak to the exte-rior of the engine. The HPOP willonly leak when there is an internal

The base of Caterpillar’s rear seal installer is bolted to therear of the crankshaft.

The one-piece steel piston design is produced by (center) inertia/friction welding a steel crown to a steel piston skirt. This de-sign creates a piston with an internal oil cooling gallery in the crown (right), and increased structural strength and resistance tofatigue.

The rear seal is installed over the installer base. An outersleeve will be used with an impact wrench to install the sealinto its proper position.


seal problem, which is an indicator of an upcomingHPOP failure. This new design of HPOP also incorpo-rated a different regulator system, however, this style ofnew pump was more costly to replace and could not beinterchanged with older 3126 versions.

In the second half of 2003, Cat released the replace-ment for the 3126 version, known as the C7.

Once again, you can see the trend as demand rises.Whether the circumstance involves making more poweror keeping compliant with growing emissions standards;in order to compete, things must change. The C7 wasCaterpillar’s answer to the Tier 4 standard that would berequired for 2004. The engine used the same configura-tion as the 3126 version, but the fuel system waschanged, utilizing a new style of HEUI injector. The elec-tronics were also more intense to offer further fuel con-trol and electronic additions to the engine. The controllerwas upgraded to a 120 pin connection with much fasterprocessing speeds.

One of the electronic additions is known as the Cat

18 November 2012 | EngineBuilderCircle 118 for more information

Rod caps and rods are color coded so that they can bematched during installation and assure correct tolerances fora smooth running engine.

To ensure that the block issalvageable it should bemeasured with a digital discbrake caliper to determineif the wall thickness can ac-cept a repair sleeve.

ACERT System – Advanced Combustion Emissions Re-duction Technology – involves the precise control of thecombustion cycle by controlling incoming air and fuel,as well as exhaust aftertreatment. The new HEUI injec-tor and electronics allow for multiple injections, differentfuel rate strategies which help improve combustion.

In 2007, the C7 would change again, this time to ad-just to the fuel, not just to market demands. You have toremember that in 2007, diesel fuel would change toULSD (Ultra-Low Sulfur Diesel). With this change,Caterpillar changed the fuel system of the C7 to com-mon-rail injection. The common-rail injection took injec-tion pressures to 27,500 psi. The transfer pump suppliesfuel to the fuel rail at 280 psi. The reduction of sulfur lev-els in ULSD means less lubricity, so circulating the fuelrapidly at high pressure keeps heat down. The tur-bocharger was changed to variable nozzle technology,which can offer proper amounts of boost at all enginespeeds. What is really impressive is that these engines


Camshaft end play is inspected with a dial indicator andrecorded on a Quality Control Card.

Piston height is inspected with a dial indicator and recordedon a Quality Control Card.

Circle 119 for more information

can have a service life of 450,000 to500,000 miles on a blend of B50 bio-diesel.

The 3126 and the C7 configura-tions share many similarities. Thebore is 4.330˝ and the stroke is 5.000˝.The compression ratio was 16.5:1.The cylinder block has “parent” bore

cylinders, meaning it does not havereplaceable liners, but the cylinderscan be sleeved if necessary. Beforeboring the cylinder block to acceptrepair sleeves, follow the OE guide-lines to ensure that the block is sal-vageable. One guideline in particularexplains that the cylinder blockshould be measured with a digitaldisc brake caliper to determine if thecylinder wall thickness is thickenough to accept a cylinder repairsleeve.

Insert the thinner leg of the caliperapproximately 1.25” into the waterpassage at the front between of eachcylinder. The block must be a mini-mum of 0.170” (4.3mm) for the blockto be salvageable. The use of a stressplate is also recommended for meas-uring & honing the cylinder diame-ters.

The single cylinder head is similarto the late 3126B heads, with 3 valvesper cylinder (one exhaust valve and2 intake valves). The electronically-actuated injectors are located be-tween the three valves. A commonpush rod and rocker arm design op-erates the valves, driven from acamshaft located in the cylinderblock. The head is a cross flow de-sign, with the intake ports located onthe left side, and the exhaust portson the right. There are provisions onthe left side of the cylinder head forthe high-pressure fuel lines. The ex-haust rockers incorporate smallspray holes that are used to cool theinjectors. The front cover haschanged to incorporate the high-pressure fuel delivery system.

But there are some differences aswell. The connecting rods and crank-shaft still share the same journalsizes but have some changes also.The counterweights of the crankshaftare smaller to accommodate a lighterpiston design. The rods are notforged as previous versions were butare now powdered metal with a“cracked cap” design. There are twodifferent sizes of the small end of theconnecting rod, depending on thepiston used.

The C7 used two different pistonsdepending on its horsepower. Thereis a short one-piece aluminum piston

for 210 hp and below engines that in-corporates a smaller 1.5˝ diameterwristpin. There is a taller aluminumpiston with a 1.811˝ wrist pin diame-ter for 230 hp and higher versions. Asteel piston is used with the smaller1.5˝ wristpin design for smaller hpapplications.

The front gear train of the enginehas changed which includes fewerteeth and a more coarse design. Thisis so that these gear designs cannotbe interchanged with older versions.The front gear train drives thecamshaft, oil pump, accessory drives,


The Cat C7 Was AvailableWith These Horsepower Ratings:

210, 230, 250, 275, 300, 330, 350and 360 hp

Torque ratings ranged from520 up to 925 lb-ft. The 201,230 and 250 hp. ratings wereavailable in either a lowtorque or high torque option.

The choice of torque options allowed differenttransmissions, which are ratedby torque capacity, to bematched with the C7. The 330through 360 horsepowerratings were only available inRV and firetruck applications.

Main bearings are lubricated after in-stallation as they are readied to re-ceive the crankshaft.

Journals are lubricated after installa-tion and prior to the installation of themain caps.

Crankshaft end play is inspected witha dial indicator and recorded on aQuality Control Card.

and the high pressure fuel pump forthe common rail fuel system.In addi-tion, the oil pump now produces ahigher volume.

Many C7 engines are now facingthe need of a rebuild. Most of theseengines see a service life of around500,000 miles. In researching this ar-ticle, Bill Wessel and others at JasperEngines and Transmissions in Jasper,IN, explained that they have takenon production of the Cat C7 to meetthe changing needs of the diesel en-gine aftermarket.

Jasper incorporates precision ma-chining and quality parts on the re-build of each C7 as they do with theother engines that they stand behind,and Wessel offers some tips. Eventhough the cylinders are not sleeved,

the block can safely be bored. Thecylinder block is torque plate honedso there will not be any cylinder dis-tortion. The high pressure fuel linesare also replaced. Cat recommendsthis if they are ever removed.

Cat itself does not offer any gasketsets for this engine, so Jasper isworking with leading gasket manu-facturers to offer complete gasketsets needed for use during the en-gine install process. Other replace-ment parts are available for thisengine in the aftermarket as well.

Special thanks to Bill Wessel, BradBoeglin, Chip Helderman, Jimmy Corbinand Mike Pfau from Jasper and SteveScott from IPD LLC for their assistancewith this article. ■


Rocker side play is inspected and adjusted to correct tolerances.

The Basic C7 Engine Features An In-Line Six-Cylinder And Four-Stroke Diesel Engine

The C7 model sets up as a turbo-charged engine, and the officialcompression ratio comes in at an impressive 16.5:1. The coolingsystem holds 3.5 gallons, while the lube oil system holds 5.5gallons to ensure everything runs smoothly. These heavy enginesweigh over half a ton with the flywheel, coming in at 1,295pounds according to company specifications.

ACERTThe ACERT technology combinesadvances in four critical enginesystems: air intake, fuel, electroniccontrols and exhaust aftertreatment.The air intake system uses

traditional wastegatedturbochargers to boost air intakepressures. The medium-dutyengines uses a single turbocharger,and the heavy-duty engines usetwo turbochargers working inseries. Cat uses variable valveactuation controlled by the engineelectronics to adjust the amount ofair that enters the cylinders foroptimum combustion. The variablevalve actuation will also allow Cat tooffer an optional integralcompression brake on two of theirheavy-duty engines.The fuel system uses existing

hydraulically actuated,electronically controlled unitinjectors on medium-duty engines,and mechanically actuated,electronically controlled unitinjectors on heavy-duty engines.The two injection systems havebeen modified with multipleinjection technology that pulsesmultiple bursts of fuel to producemore complete combustion.The electronic controls use the

same hardware found on previousCat engines, but they have re-programmed software to controlthe various new components andsystems.Finally, the exhaust after-

treatment package consists of adiesel oxidation catalyst to reduceparticulates. This device has beenused on certain Cat engines forseveral years with great success. Itis incorporated into the mufflerand requires no maintenance orcleaning. Cat says the expected lifeof the aftertreatment unit is equalto the life of the engine itself.

Typically the questions with astroker are, ‘How big can youmake it?’; ‘How big do you

want it?’; and ‘How are you goingto swing all that mass in there?’”explains John Nijssen, aka StrokerJohn. The Apple Valley, CA-basedengine builder operates stro-kerengine.com and builds domesticV8 engines for the U.S. and interna-tional (primarilyAustralian) en-thusiast mar-kets.

He says hedoesn’t try topush his desireonto the customer. “Idon’t sell you what Ilike, but rather youand I figure out whatyou really need forpower and price,” Nijssen says.

“Customers (I prefer to call them‘clients’) enjoy discussing their en-gine build. I ask them what theywant the new motor to do for them.From there I can make recommen-dations and ask for their approval,”he says.

Nijssen considers himself a cus-tom engine builder, rather than abuilder of crate motors. “I try tobuild the best possible combina-tions within the limits of the client'sbudget.”

“The main purpose of a strokerengine is to make more power. Mycompany motto is ‘Bigger enginesmake more power.’ What does thatreally mean? When I talk aboutpower, I’m typically talking abouttorque.

“In Ford, I do the 302 block as331 or 347 like everyone else,” heexplains. “With a Windsor, the 408and 418 work very well. If youwant more torque this block will go427 and 434. If we step up and use aDart block, 467 is about the limit. Imade 711 hp at 6400 rpm with aYates Wedge cut head on a 463

Clevor. The 460 block works well asa 545, and with the Kaase P51 headsmakes an effortless 600 horse-power.”

Nijssen says, “I do not ‘sell en-gines’ – I build engines. Mostly,

they’re street/stripcombina-

tions,both lowercost ‘budget’ mo-tors and maximummonster power makers.” His shopis a small operation specializing inpowerful street V8 engines to meetspecific needs, either massive lowspeed torque or upper rpm horse-power.

“If you increase the cubic inchdisplacement of the engine itshould make more power. Obvi-ously a 460 engine will have a lotmore pulling power at 2,500 rpmthan a 302 will – common sensetells you that and it happens in thereal world.”

Nijssen says you can typically es-timate the torque that an enginewill put out based on a very simpleformula: stock heads will typicallymake 1 foot pound of torque percubic inch, so a 302 is usually capa-

ble of putting out about 300 lb.ft. If you get a set of performance

heads and raise the compressionratio, you’ll typically make about1.25 to 1.3 lb.ft. of torque per cubicinch. So a 302 at the smaller numberequals about 377 foot pounds oftorque over the stock heads (Editor’snote: see Larry Carley’s article on

cylinder heads in the March ’12issue of Engine Builder maga-zine for more information.)

Another way of increasingtorque is to raise the compres-sion ratio, explains Nijssen.“There are limits on what youcan do with the compression

ratio, however, before yourun into detonation. Deto-

nation is connected to fueland is keyed to the oc-

tane rating.” Weknow from expe-rience that the

maximum com-pression ratio we can run

based on the fuel the cus-tomer plans to run is a set

number – that number is a vari-ance based on the engine build.”Nijssen says each full compres-

sion ratio increase is worth power.“That is to say, going from 9:1 to10:1 or from 10:1 to 11:1 is worthfour percent more power each time,pretty much across the rpm range.For example, if we have an enginemaking 500 hp at 10:1, and we raisethe compression ratio to 11, wewould gain four percent morepower or 20 hp. That’s not atremendous gain, so if we raise it to11:1 and it starts detonating, notonly would you not make the extra20, you would lose some of the 500you had because detonation is notburning the fuel causing expansionand power, but exploding it causingshock and damage. So, we tend tobuild motors conservatively, keep-ing them in the safe zone, perhaps10.7:1, leaving that .3 as a safety


EDITOR Doug Kaufman [email protected]

margin and the power loss is like1.2%, not enough to worry about.”

The choice, explains Nijssen, be-comes, how much cubic inch in-crease do you want and how muchcan you fit in the block? When youincrease cubic inch capacity of theengine you’ll make more torque. Itdoesn’t matter if you’re doing thatby increasing the bore or the stroke.There is a direct relationship be-tween torque and cid (cubic inchdisplacement) as long as the cidcomes up the same; the torque out-put increase will be the same. Ifyou’re making 1 foot pound oftorque per cubic inch and you mul-tiply it by 350 it doesn’t matter if ithas a 4-inch bore and a 3.5-inchcrank or a 3-inch crank and a 4.3-inch bore.

However the power curve be-tween the two combinations lookdifferent. The shorter stoker largerbore motor will produce less torqueat lower rpm and peak at a higherrpm than the long stroke combina-tion. This is why in part dieselmotor utilizes very long stroker,more torque or pulling power atlow speed. Nijssen acknowledgesthat if the discussion has been cen-tered on the same cid engine, “Youmight say ‘I want the bigger bore

combination,’” he says. “Great…soyou go out and buy an aftermarketblock.

“Now we can take a 351 W froma 4.030˝ optimal bore size to 4.155˝(a .030˝ over) or some blocks youcould push it out to 4.200˝. So in-

stead of a small bore with a plus1/2˝ stroked 408 ‘stump puller’ youcan build a 1/8˝ stroked 402‘screamer.’”

“But once you have a nice bigbore block what happens if you putthe big crank in there as well? “Wellthen you can go from a 434, whichis the biggest crank you could putin there to a 471 cid motor,” he says.“For the street, because most of thetime you’re driving around in the2,000-4,000 rpm range, having thebig stroke crank will pay off moreoften. On an oval track, having ashorter stroke will have the advan-tage because you’re not only deal-ing so much with torque productionand acceleration you’re dealingwith miles per hour and the issuesinvolved with that.”

For drag racing Nijssen saysthere’s a balance between thelongest possible stroke and some-thing a little less.

“Choosing the stroke has a lot todo with the maximum rpm require-ment of the engine. For example, inthe Ford family on a Windsor block,I might encourage the use of a4.000˝ stroke crankshaft to turn to


“Stroker John,” John Nijssen.

The small block Chevy has a valve angle of 23 degrees; the small block Ford has avalve angle of 21 degrees. When you have less valve angle the turn from the portinto the valve pocket isn’t as severe. Aftermarket heads often have valve angles of14 degrees and 11 degrees. So, the Ford heads have a slight advantage over theChevy heads due to the valve angle.

7,000 rpm, whereas on the street, Imight want to suggest a 4.100˝stroke crank to turn to, say, 6,500 orI might even suggest a 4.250˝ strokeif we’re only going to 6,000 rpm be-cause of the frictional loss concerns.

“However, while a longer strokecrankshaft tends to make moretorque early on in the rpm range,and about the same amount oftorque at peak horsepower,” Ni-jssen continues. “But what happensis, the longer stroke crank pulls thepiston down the cylinder a longerdistance. You’re dragging the ringsfurther, so friction becomes an in-creasing problem as rpm increasesbecause it’s putting the brakes onand it’s absorbing more energy. Asthe rpm goes up it’s robbing moreand more power – they call it fric-tion horsepower – like anti-horse-power.”

Nijssen says that since the pistonhas to travel a greater distance inthe same half a revolution, then ac-celerate from a dead stop, then stopit and start it again – it requiresmore energy usage, so it losespower again.

“A longer stroke crank won’tmake the same amount of torque atthe higher rpm so it won’t multiplyout into horsepower, he says. “Thebigger bore, shorter stroke motorwill typically make more horse-power and if max rpm is a concernit will have an advantage. But forsheer acceleration off the line and60 foot times it’s hard to beat thelong stroke small bore because itwill just push you back in the seat

harder as it accelerates from 2,000rpm up. But once you pull it out ofgear at 6,000 and put it in 2nd gearit drops down to 5,000 rpm and it’snow operating at a higher rpmrange and will do so through all thegears until you lift your foot. So abigger bore short stroke motor willhave an advantage.”

Nijssen says another point toconsider on the particularly longstroke motors is the feet per secondtravel of the piston.

“There are limits to how fast apiston should be accelerated anddecelerated,” he cautions. “Thereare structural limitations of all theinternal components.”

You can typically buy a 2618forged piston that can handle a lotof abuse. Pistons seldom fail;they’re usually destroyed by some-thing else going wrong. So if youwere to rev the engine particularlyhigh you would want to use a bet-ter quality crankshaft, typicallyAmerican made, than say a cheapercrankshaft.”When it comes to com-paring a Ford stroker to a Chevroletstroker for the street, there are otherissues involved. For example, theangle of the valves plays an impor-tant role. The small block Chevyhas a valve angle of 23 degrees; thesmall block Ford has a valve angleof 21 degrees. When you have lessvalve angle the turn from the portinto the valve pocket isn’t as severe.Nijssen says this is an importantpoint.

“Aftermarket modified racingheads often have valve angles of 14degrees and 11 degrees – when youlook at the cylinder head itself theintake port is standing up more to-ward the vertical making the headsvery tall, and the exhaust side be-comes very long, in comparison. So,the Ford heads have a slight advan-tage over the Chevy heads due tothe valve angle, he says.

“In the case of a Cleveland cylin-der head, because the valve iscanted on a second angle, there areother benefits as well. The incomingair stream doesn’t just flow straightin, arriving 90 degrees over the topof the piston – you’re tipping it a

little more toward the center of thecylinder, which helps the air swirlaround in the cylinder as it comesin. Like water going down thedrain, it swirls around going intothe cylinder, which is good forkeeping the air and the fuel thor-oughly mixed up. Homogenizationis maintained so you don’t get richand lean pockets throughout theair-fuel charge,” he says.

Rotating AssembliesTypically, says Nijssen, you can puta pretty big crank in a small blockand rev it to 7,000 rpm. “But whenwe get into the big blocks and westart putting in 4.500˝ or 4.750˝strokes, that rpm limit starts com-ing down to 6,500 to 6,000 rpm. Ifyou’re using an iron crankshaft,6,000 rpm would be the limit. Sowhen choosing a stroke length, youhave to pay attention to rpm andthat may be a limitation.”

Another consideration is rodangle: often referred to as rod tostroke ratio, he explains. When thecrankshaft is rotated 45 degrees and


Limitations to a stroker include strikingthe oil pan. Nijssen says sometimes hecan cut into the oil pan rail as long asthere’s not a bolt there.

You can put a pretty big crank in a smallblock and rev it to 7,000 rpm. But whenyou put in 4.500˝ or 4.750˝ strokes in abig block, that rpm limit starts comingdown to 6,500 - 6,000 rpm. If you’reusing an iron crankshaft, 6,000 rpmwould be the limit, says Nijssen.

the piston is halfway down thecylinder traveling at maximumspeed just before it begins to decel-erate as it nears the bottom, the rodtips over on an angle. As you in-crease the stroke length the rodangle is increased. So it’s desirableto increase the rod length to takesome of that angle out of the rod,because it is transferred to side loador thrust against the piston.

“It’s pushing the piston harderand harder against the cylinderwall as the stroke is increased. Onceagain, that’s friction and wear. Sowe want to increase the rod lengthwhen we increase the strokelength,” Nijssen says. “The limita-tion of that becomes the block deckheight. Basically it all has to fit inthe block.

“Custom pistons provide the so-lution to many combinations andwe want to use the longest rodlength we can. We have some dis-cretion with the piston compressionheight. The question is whetherthere is enough material on the pis-ton to fit the rings in and allow thevalve pockets to be strongenough?” he says. “We’re limitedby two factors when it comes to pis-ton compression heights: we haveto fit all three rings between thewrist pin and the top of the piston

and have enough thickness betweenthem for the ring lands to be strongenough to support them all. We canraise the wrist pin up into the oilring groove almost to the top of theoil ring groove. We can compensatefor the cut by putting in a steel railthat covers the wrist pin area thatwas cut out. The steel spacer ringhelps support the area that was cutout.”

Nijssen suggests that when thereare concerns about negative side ef-fects or effectiveness of a workingcomponent it simply comes downto a debate over which is more im-portant: making more power or en-durance?

“The other consideration withpistons is valve pocket depth. Thisis not usually a concern with aWindsor but if you have a Cleve-land, which tips the valve over onan angle, now the valve pocket isextended over into the side of thepiston where the top ring is. So youhave to have enough material in thetop of the piston to put the valvepocket in place without touchingthe top ring,” he says. “Typicallyyou could perhaps get a Windsorpiston with a shorter compressionheight than a Cleveland piston.Custom pistons allow you to mini-mize the piston squish height, al-

lowing the piston to reach the topof the cylinder bore.” says Nijssen.

“Typically when we’re buildingstreet engines we’re going for thebig power increases. We’re notchasing three horsepower, that’s forracing applications where every-thing is on the line,” he says.

From a stroking point of viewone of the most significant differ-ences in deciding to build a Fordover Chevy comes to block con-struction. “A Ford 302 can’t be aslarge as a small block Chevy (SBC)stroker but a Windsor motor can besubstantially larger than a SBC stro-ker. The Windsor is a taller block, soyou can put a longer stroke crank-shaft in it,” explains Nijssen.

“Typically, a factory Chevy canbe stroked to a 383. You can takethem to 396 and 408 although you’llbe pouring block fill in the bottomof the block so you can grind clear-ances into the bottom of the blockinto the water jacket and not havewater pouring out. This isn’t as biga problem for Ford because of theway the blocks are cast – you cancut a fairly substantial groove in thebottom of the cylinder and still notbe near the water jacket,” he says.

In addition, the Windsor blockhas a higher camshaft height thanthe comparable Chevrolet. “Whenyou’re building a Chevy you firsthave to consider adding the extraclearance for the rod when it comesaround, otherwise, when the rodcomes around, the nut will collidewith the bottom of the cylinder;then you have to grind the corneroff the other end of the bolt on theother side so it won’t collide withthe camshaft. You hear about smallbase circle camshafts – this providesmore clearance for the rod on thecam lobe rather than on the con-necting rod.”

Nijssen suggests that when usinga connecting rod with a cap screwbolt on it, you have more clearanceroom for the camshaft and you’re notcompromising the bolt by grindingpart of it away. “On a Ford this is al-most no problem at all because thecamshaft is so high up that you won’tget interference even with a very long


Nijssen says he the Ford 302 block as 331 or 347 like everyone else. With a Windsor,the 408 and 418 work very well. If you want more torque this block will go 427 and434. If want to step up and use a Dart block, 467 is about the limit, he says.

stroke you can put in a Ford block.”Limitations to a stroker include

striking the oil pan. You can’t goout through the oil pan rail, but Ni-jssen says sometimes he can cut intothe oil pan rail as long as there’s nota bolt there. In addition, aftermar-ket oil pan makers often form addi-tional clearance into the side of theoil pan.

He cautions, however, that youneed to be careful about how faryou’ll pull the piston down the bot-tom of the cylinder. If your connect-ing rod is too short, even if it doesn’thit the counterweight, you may findyou’re pulling the piston out the bot-tom of the cylinder further than youwant to. And the piston may rock andas it comes back into the cylinder andit can scrape the piston skirt andthereby damage it.

An example is with Clevelands. A4.000˝ stroke 6.000˝ rod does not clearthe counterweight on all brands ofcrankshafts. Often the part numberreflects the rod length – p/n 4006200for example, indicates a 6.200˝ longrod. Using a 6.000˝ will not work.

When choosing cranks, particu-larly longer stroke cranks, you runinto the balancing issue. Ford typi-

cally has external balanced cranks inall of its motors, Nijssen explains.“When you go to an aftermarketcrank and increase the stroke, itmakes the crankshaft inherently heav-ier on the connecting rod side of thecrank since you have more metalgoing out in that direction. Thereforeas the stroke increases you start tofind the weight of the counterweightis inadequate.

According to Nijssen, with an af-termarket crankshaft you might wantto have it internally balanced eventhough the factory crankshaft was ex-ternally balanced. “You decidewhether you’ll want to take advan-tage of that or just go ahead and usethe factory harmonic balancer andflexplate and drill the counterweightlike Swiss cheese,” he says.

“As you increase the cubic inchdisplacement,” he says, “not only doyou want to increase the rod length,you want to change the camshaft du-ration. Because the engine is larger itneeds a bigger gulp of air to producepower at the same rpm than a stan-dard stroke engine. And a bigger en-gine wants bigger ports to feed it, soonce again, if you use the same headas on the stock engine, you’ll want to

increase the camshaft duration. If youcan put a larger cylinder head youmight be able to keep the same dura-tion.”

“I started out in this field as an ap-prentice automotive machinist inNew Zealand in 1977. I graduatedfirst in my class 1980 and moved tothe U.S. in 1982,” Nijssen explains. “Iworked in various machine shops formany years until 2001 when I decidedto start building custom high per-formance engines for those whowhere looking for something morethan the typical crate engine combina-tion.”

Nijssen suggests that stroker en-gine builders caution their customersthat replacing an engine with a morepowerful stroker engine may requireincreasing the strength of relatedcomponents, such as the transmis-sion, U-joints, driveshaft, differentialand axles. It may also be a good ideato improve the brakes, and if you addenough extra power, you may need tostiffen the chassis frame rails.

In addition, traction may become aproblem. Slicks increase stress, whereas smoking street tires ease this loadon the drive train.

“Long duration camshafts may re-quire a higher stall torque converter,and high compression ratios will re-quire racing gas or octane boasters. Besure you plan your engine combina-tion carefully,” he says.

“High compression ratios, longduration camshafts high speed torqueconverters work well when racing,but can just waste gas, and be a painto drive in stop and go commuting towork traffic,” he says. “Sometimes,the best thing is to explain to a cus-tomer that a modestly powerful en-gine may be all he needs.”

Today’s cars and trucks use elec-tronic fuel injection (EFI) which re-quire ECU reprogramming, andStates with smog regulations limit en-gine modification, but these are sub-jects of another discussion.

Finally Nijssen suggests you doyour math, consider the applicationand enjoy building more powereiyh your Ford Strokers. ■


Nijssen suggests that stroker engine builders caution customers that replacing an en-gine with a more powerful stroker engine may require increasing the strength of re-lated components, such as the transmission, U-joints, driveshaft, differential and axles.

Engine Rebuilding Technical Guide, 11.2012

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Transcript of Engine Rebuilding Technical Guide, 11.2012