LS4 build

[FieroWanaBe1]

I wanted to share my slow build-up of my LS4 engine, it's a little unorthodox.
My goal is to build a bullet-proof LS4. Mostly road course track-day use, limited street driving, Mated to a “Close-Ratio” geared, Quaife equipped F40: 14.74:1, 7.98:1, 5.36:1, 4.11:1, 3.32:1, 2.44:1
I've scoured part options to find the lightest, and most economical combination of parts.
Block: Flashing Cleanup, .020 Overbore (possible with factory sleeves), factory caps, ProComp Main studs and ARP Head Bolts. You can find a seller online machining these blocks for $800 Shipped. This is cheaper than taking any block to the machine shop.
Crankshaft: GM-12641690 (3.622 Stroke, LS3 Dry Sump, 58X wheel, (Same 4140 forging as LS9) with 8 bolt pattern. This is the best way to get a forged crank for an LS motor for less than $500. The factory LS4 crank is not going to work on this engine combination.
Oil Pump: GM Factory LS7/LS3 2 Stage Pump. Hand Ported.
Oil Pan: Factory LS3 dry sump pan and oil tank, Improved racing windage tray w/ trap doors and ls9 thermostatic oil cooler.
Rods: Chinesium LG3-6125LSI 4340 I beams 6.125" (605g) RPM International Rods (these look identical to ProComp Rods, and came with a balance sheet of +/-1gm. These, besides expensive billet I-beams, are the lightest, and cheapest on-center forged rods I could find.
Pistons: Mahle Forged 5.3L piston 3.800 Bore for use with 6.125 Rod with a .927 Pin, and 1.0, 1.0, 2.0 ring pack, to achieve an 10:1 compression ratio. From my searches, MAHLE is best cost per Weight for 2618 pistons, weight should be 427grams
Heads: GM 243 Castings, hand ported with rocker stud boss removal, slight swirl ramp reduction, and bowl cleanup. Valve Job Needed.
Push-Rods: Will need to measure for length, most likely Comp 5/16 pushrod.
Rockers: BTR Shaft System with BTR Rockers for Added durability over .600 lift
Valves: Stock GM LS6 Hollow Stem Intake (75g) and Sodium Filled Exhaust (66g)
Springs: BTR .625" Lift Beehive Springs, using Brian Tooley Racing Ti Retainers (4.5g) with factory 7 degree locks (1g).
Intake: TBSS for now, Looking into the BTR Equalizer.
Exhaust: LS7/LS9 Manifolds.
Cooling System: Meziere remote mechanical water pump WP430-S, Summit Manifold, Moroso remote thermostat housing 63425.
Ignition: Factory GM LS4 coils
ECU: Maybe Haltech Rebel LS
Bearings: Calico Coated Clevite Tri-Metal Bearings.
Timing Chain: C7-R Timing Chain
Camshaft: I am still narrowing my search down on the camshafts.
Dyno Testing To Do
Jegs 454LSX Clone
Sloppy Stage 3
Sloppy Best "import"
Sloppy Coppy Stages 1 and 2 fresh off the boat from Wuhan.
Lifters: Delphi "LS7"


edit: rods, most aftermarket rods have a .030" offset to the big end for SBC applications. (Scat uses .015 and is "useable of both SBC and LSx apps for their I beams)

EDIT 10-22-24 Build list updated

[FieroWanaBe1]

I don't think the rods I want to use will work for me.
The probe SBC 6.125 Ultralight I beams for an SBC weigh about 565g
SBC rods have a offset on the big end (coaxial to the crank shaft and piston pin) of .030"
LS rods have no big end offset.
There are other I beams out there that might work that have no offset, and aren't too expensive, they are about 605g each. Its unverified at this point that the GM Connecting rod weighs about 650g. So I can still save weight and upgrade the rod.
Some Chinesium rods:
http://www.racingpartsmaximum.com/sae4340ibeam-2.html
they weigh 605g according to the tech support.
And i found these, suspiciously i think they come from the same place.
http://www.vigilanteparts.com/Vigilante ... -10049.htm

I have emailed a couple places selling lightweight I-beams if they have no-offset rods in 6.125. We shall see.

[FieroWanaBe1]

I confirmed the factory rod weight is 650g

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[The Dark Side of Will]

If you're going to an actual shallow-pan dry sump, will you do anything to lower the engine in the car? That's one of the huge advantages of a dry sump system.

[FieroWanaBe1]

I dont think the LS7 oil pan is any shallower than a wet sump LS3 corvette pan, which has a height of 5". I can snap picutres comparing the LS4 pan to the LS7/LS3 Dry Sump pan.

[FieroWanaBe1]

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Factory flat top 3.780 piston weight and pin weight.

[The Dark Side of Will]

What are your goals or objectives? Do you have an RPM target?

In a pushrod engine, RPM is more about the valvetrain than the rotating assembly.

A stock LS rotating assembly with ARP rod bolts will turn 7000 reliably.

Really, if you get lightweight high compression pistons, you'll have gone as far as you need to go for the use case you've outlined. I'd go for 11.5 to 11.8:1 in your shoes, though.

You're also dealing with cathedral port heads, which are very good, but aren't as good as LS7/3/9/A style heads and will limit the engine's extreme RPM potential.

[FieroWanaBe1]

My power goal is 450whp, and as much reliability that I can afford. To me that means checking every box as far as efficiency, optimizing, and attention to detail. Really,For the cost of the overseas forged I beams, I would end up being very close to what it would cost for me to install the ARP bolts, and then have the rods re-honed with more clamp load.

As far as valve train stability, I'm using the LS6 hollow stem intake and sodium filled exhaust valves, short of titanium ($),these are the lightest "available" valves out there that I found. I found mine used on eBay. The BTR Ti retainers are some of the lightest I found in my search, and can work with the stock locks, which are very light already. Even the PAC race springs are a few grams lighter than stock. The factory rockers are also pretty low inertia, and very stiff. One piece pushrods should save weight.
I am limiting myself to .600" of lift to save wear on the valve guides and tips and rocker fulcrums, they were not design with high lift in mind.
And I'm leaning towards tie bar lifters to avoid the possibility of lifters rotating in the factory style plastic trays. But, at .600 lift, maybe it is less of a concern.


Being that the LS4 is a bastard engine, it cannot be dry sleeved like other Gen IV 5.3L blocks, the cylinders are not siamesed, its similar to a GEN III, where past the deck the cooling jacket is open between cylinders, the block does have bay to bay windows, but they do not have the radius that was added to the LS3 block, and the hone head clearance radius is 3mm, unlike the 10mm of the LS3 and LS7 block.
The short of it is, unless you want to spend big bucks, the LS4 is stuck with a 3.780 (maybe 3.790) bore and using Cathedral heads, with a maximum valve diameter of 2.00 on the intake and 1.55 on the exhaust. No rectangle port heads for me.

[The Dark Side of Will]

The big deal with rod bolt clamp load is preventing cap fret and the resulting possibility of spinning a bearing.

Cracked cap rods DO NOT FRET. That failure mode has been eliminated.

Therefore you don't need to go insane with the clamp load on the rod bolts. LS rods don't need to be resized with only a little more clamp load than stock.

Why upgrade then? Stock torque to yield rod bolts are closer to their ultimate limits, so running them higher than stock can take them over that limit and operate them in a low cycle fatigue condition resulting in failure.

Basically, the vast majority of builds waste money putting aftermarket rods in an LS.

You really need to set an RPM limit and design your valvetrain to that. OE rockers are well engineered for OE spring loads. Yes, you're using LS6 valves, but GM didn't turn the LS6 to 7000 RPM from the factory. Why not? Is the weak point the rockers at a spring load that will support 7000 RPM reliably?

[FieroWanaBe1]

I have given myself 7500 rpm limit. I think thats the practical limit without going to crazy on parts.
http://www.superchevy.com/how-to/0901gm ... ine-build/
Here is a decent tech article explaining what Katech did to make the LS2 live in the Cadillac GT cars. My goal is to mimic the valve train there. However katech ditched the plastic trays, the gm racing lifters are not avaiable as tie bar lifters, and have a smaller roller than most aftermarket lifters. I also am trying to find out more about adding roller cam bearings to the LS4 block, its closer to a LS6 block than a LS2, and I really have only heard of Gen IV engines being machined for roller cam bearings. Builders on LS1tech also claim coated cam bearings have made roller bearings a lot less necessary. But the reduction in oil heat alone might make the change worthwhile.

Related, my dry sump system will not create much if any crankcase vacuum, therefore, I am thinking I can get away without piston oilers and the pins wont seize. GM didnt find them necessary on The LS7 engine. I would like to have conversation with someone in the know at Katech to get their input on what would benefit me for high speed operation.
Here is GM's patent for a piston oiler system for Gen III engines. Too bad they never made it available.
www.google.com/patents/US6955142?dq=us0 ... sQ6AEIHTAA

In 2008 GM did update the rod bolts to higher strength material and with more fatigue resistance in the design of the thread root.
http://www.corvetteactioncenter.com/spe ... 8/ls3.html
My 2006 motor does not have this update.
When I installed ARP rods in my LQ1, it was necesarry to have the rods honed; the machine shop found them to be a couple thousand out of round, if I recall correctly.

[fieroguru]

Looks like a fun build! I am curious to see the final result.
Given the durability of the Gen IV LS engines and how inexpensive they are to buy used, I wouldn't touch the bottom end and focus all your efforts on the intake, heads, camshaft, and exhaust.

How did you figure out the wet sleeve issue? Run a scope down one of the cooling jackets and saw the backside of the sleeve?

[FieroWanaBe1]

There are posts on LS1tech From Race Engine Development describing the issue, and I verified it by running some wire between the sleeves in the cooling jacket.

The LS4 block is a non siameesed Gen III internally. It is MID or wet sleeve only.

Most but not all 5.3 L aluminum truck blocks are Gen IV castings and can be dry sleeved to 4.185" bore. I sleeve a lot of these. Just picked up another core over the weekend. 

The front drive LS4 block has a completely different rear bolt pattern from the rear drive blocks we are all familiar with. If I remember correctly (been a while since I had an LS4 block here) the engine mounting points on the side of the block are different as well. 

Steve

From <https://ls1tech.com/forums/generation-i ... st16550012>

If you shine a penlight between the cylinders from the deck, it becomes obvious that dry sleeves aren't possible.

[The Dark Side of Will]

If you're looking for "reliability" look into something like this: http://www.raceindustry.com/part-showca ... aster.html
These are for race engines running 0.800+" of lift with high acceleration ramp rates that can beat the needles in conventional roller lifters literally to death. The idea is beautifully elegant and they shouldn't take any machining to install... I don't know if they're made for Gen III/IV engines, though.

Roller cam bearings are for 9500 RPM engines, not 7500 RPM engines. If you're not running the valve spring loads for extreme lift at extreme RPM, you don't need roller cam bearings.

At some point I'll tear an LS apart and measure for myself, but the basic set of ARP bolts are supposed to be drop-in. There are more expensive sets that aren't, but the basic ones are billed as such.

[FieroWanaBe1]

Being as I am using an LS3 specific crankshaft, and my power/speed goals would dictate it, I need to have my bottom end balanced for the small bore pistons regardless. Forged pistons are good insurance if I am to run at high speeed for long durations. At least when compared to the typical 1/4 mile runs. Broken parts would end up costong more money in the long run. Rods might not be necessary, but I feel pistons are. Im definitely giving the valvetrain a lot of attention here, and am trying to find everythong i can that cuts weight, and wont give me overkill for spring pressures, that equates to more wear and friction. Going to a slightly longer rod, I can change to a smaller and lighter pin, and reduce side loading on the cylinder just a smal amount. The lighter piston assembly will lower rod bearing stress at high speed, more insurance against spinning a rod bearing.

[FieroWanaBe1]

Roller cam bearings are for 9500 RPM engines, not 7500 RPM engines. If you're not running the valve spring loads for extreme lift at extreme RPM, you don't need roller cam bearings.

I really only considered it becuase Katech found it necessary on their road race motors. And those motors are used in 30-60 minute SCCA races. The Cam used isnt high lift, it is the GM showroom stock cam. About .570 valve lift and 238/251 duration on a 106 center. A bit pricey from GM though.

At some point I'll tear an LS apart and measure for myself, but the basic set of ARP bolts are supposed to be drop-in. There are more expensive sets that aren't, but the basic ones are billed as such.

Its my understanding that they are drop in. But without using extra clamp load higher proof strength fasteners are supposed to provide, bolts of the same general diameter provide no more insurance to a joint. The modulus of elasticity for alloy steels doesnt change enough to make the bolts stretch any less. and if I am to increase fastening torque to gain more clamp load, i would want to ensure the rod ends do not come out round, meaning im prpbably going to have the big ends honed regardless.

[The Dark Side of Will]

I really only considered it becuase Katech found it necessary on their road race motors. And those motors are used in 30-60 minute SCCA races. The Cam used isnt high lift, it is the GM showroom stock cam. About .570 valve lift and 238/251 duration on a 106 center. A bit pricey from GM though.

I haven't researched. What valvesprings are they using? There are LOT of people who run LS based engines on track with plain cam bearings. Are you planning to run slicks? Slicks create huge potential reliability issues in terms of keeping the engine's oil supply steady. Even the factory semi-dry sump in the C6 ZO6 and others has problems in a left hand corner at greater than 1.0 g's for more than 4 seconds.

ETA: https://www.corvetteforum.com/forums/c6 ... -data.html

Its my understanding that they are drop in. But without using extra clamp load higher proof strength fasteners are supposed to provide, bolts of the same general diameter provide no more insurance to a joint. The modulus of elasticity for alloy steels doesnt change enough to make the bolts stretch any less. and if I am to increase fastening torque to gain more clamp load, i would want to ensure the rod ends do not come out round, meaning im prpbably going to have the big ends honed regardless.

Yield stress is one thing, but fatigue limit is another. A bolt with a lower yield strength will have a lower fatigue limit. If you exceed the stock RPM limit with the lower yield bolts, the resulting increased tensile loads could be running them in a high cycle (or even low cycle) fatigue regime eventually (or quickly!) resulting in tensile failure. Replacing it with a stronger bolt pulled to the same preload means that there's greater "headroom" until the tension loads from increased RPM exceed the material's fatigue limit.

[FieroWanaBe1]

I haven't researched. What valvesprings are they using?

PAC beehives, which are around 140lb seat, and 300 nose, PSI offers similar springs with a bit more seat pressure (170?)

Even the factory semi-dry sump in the C6 ZO6 and others has problems in a left hand corner at greater than 1.0 g's for more than 4 seconds.

The dry sump tank is not baffled, and the factory "suction" stage is easy to uncover in the oil pan. The pressure side of the oil pump can easily start pumping air. GM's remedy for this on the LS9 and up iterations was increasing capacity with an additional reservoir on the tank. Improved racing and Aviad make trap door assemblies for the LS7 oil pan, and Aviad also sells a LS7 oil tank insert to aid in keeping the tank pickup covered in oil. Neither of the oil pan trap door/windage trays were designed to be used on the LS3 dry sump setup, Ill need creativity there. The left hand turn oiling issue becomes an acceleration oiling issue once installed in a Fiero. I have no intention on running slicks, The car does have on of V8Archie's widebody kits sitting in my rafters for it at the moment, so I do intend on running pretty wide rubber on the car.

I have been emailing a few shops that have some experience in LS motors to see what their pricing is for various services. Few shops by me have much. I also want to confirm that this block doesn't have the sleeve thickness available for a 3.9" bore, there are mixed opinions on LS1tech.com about what can be done with an Aluminum 5.3 block, and the LS4 is some sort of strange bastard Gen III/IV motor. eBay has really cheep sonic meters available, but I don't think they are capable of reading a curved surface. A 3.9" bore opens up the options for pistons.

[FieroWanaBe1]

LS4 intake valve, 99g

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LS6 intake valve 74g

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[FieroWanaBe1]

LS4 exhaust valve 87g

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LS6 exhaust valve 64g

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[The Dark Side of Will]

That's pretty cool. I hadn't seen numbers showing exactly how much lighter the fancy valves are