wortex

I had a very simple task from one of my shops - find a low(er) compression piston for a 2003 Z06 (LS6) so they could properly supercharge it. The request was for a 9:1 or 9.5:1 compr. ratio.
I for sure thought this would be easy job and there will be no trouble. The LS1 and LS6 was used in every Chevy Pontiac and Cadillac from mid 90's till 2004 (1996-2004) Boy, I was in for a big suprise...
It seems that the LS1/LS6 is a forgotten world in engine tuning. I have trouble locating a lower compression pistons. I called JE, Ross, Mahle, and all have nothing for these engines. No pistons, no rings, nothing.
They advertise a lot of their product for the LS1/6, but none fits without changing everything like rods, bearings, etc.
They have wrong size wrist pin a 0.927 and all LS engines from 1997 used the 0.945 diameter.
Why is it that none of the piston makers makes anything for a 12+ year old CHEVY engine ? They are trying to sell a 35 year old engine parts for this engine when it does not even fit. They made me so mad I called all of them back and filed a complain about false advertising.
Same thign with the Chrysler Hemi engines. No aftermarket pistons are available besides the MOPAR performance which is higher compression then factory oem.
All the other ones they would try and sell you require major changes to teh engine - bore it out to 0.030" and then use a different rods, use chevy bearings, etc.
I mean come on BIG TUNER GUYS, the LS series engines and the Hemi's are today best "cheap" performance engines. If they don't have anything for these then don't call yourself a "tuner" just a classic car tuner.

I'm just pissed as I thought it would be easy to modify these for the supercharger. By the way the rod they wanted to sell me for their unfit piston was Eagle performance rods with a 0.927 wrist pin.
Interestingly thats about 5% weaker then a factory LS6 Z06 rod with the 0.945 wrist pin. The Eagle rod is for the old small blocks and much stronger then those old style SB rods, but can not even match the LS6 factory rods strenght. The only reason everybody uses them because this is the only way you can use those pistons in your newer engine.


Does anybody have a lead for a correct REAL Ls1/6 pistons without using a weaker aftermarket rod ?

KCS

iTrader: (20)

No one really builds a 9:1CR engine with stock rods, so piston manufacturers don't really make shelf pistons for them. There's no demand. There are plenty of flat tops, but for a boosted engine requiring 9:1, stock rods probably aren't a good idea.

I don't know where you got the info that Eagle rods are 5% weaker than stock, but I don't think that's true. I've seen cheap Eagle H-beams (LS1 specific) handle way more power than what a stock cracked cap rod could.

The way I see it, you could either

Get shelf pistons for a .945" pin and use a 317 head with 72cc chambers to get the CR down

Get a custom set of pistons

Or get a set of forged rods and the .927" pin pistons

WhiteRhino

iTrader: (6)

I say contact Wiseco or pm Brian Nutter, as he posts on this site sometimes. I'm sure he could get you something. Even if it has to be made. From what i've seen and read. They have great customer service. As well as some of the best ls pistons out there.

itsslow98

iTrader: (18)

if the motor is being supercharged and its opened up already, i dont see why you wouldnt buy a set of forged rods for safety anyways

wortex

then most aftermarket. Totally different then a LS1 rod. Capable of handling the supercharger easily. The piston is the weakest link - aluminium hypereutectic and not forged.
The rods are not exactly H-beam rods but close to that. They are definitely reinforced compare to the LS1.

The Z06/LS6 rod has a bronze bushing at the top and oil grooves. the rod isn't the weak link at all. I talked to Lingenfelter guys before and they confirmed that the rod was absolutely not a concern. They also change the rod for one reason - no piston made for the 0.945 wrist pin with low compression.
The cometic gasket and larger head could take care of the compression issue but that is again a whole lot more expensive at the end.
a cheap insurance is what we were looking for. A 9:1 compression forged piston would have been a perfect solution in this and most average customers case. The piston being the weakest link in a supercharged setup limits the amount of boost big time. With that simple change and 600usd (set of forged piston with rings) would give you an engine that can handle 650+ HP safely.
Sure the custom pistons are the best way but I forgot to tell that time was an another factor. The #4 piston melted a few days before x-mas and we tried to have the car ready this week. Customer pistons are 4-6 weeks at least , specially during holidays.
Ross and JE for example stopped making anything for the Hemi engine. They said Chrysler will fold and will be no market for their product. So much fate in their survival...
anyway the shop is putting the forged aluminium pistons back today (Mahle) which will be slightly better as stronger then factory but the boost will have to be kept down.

I guess either you spend big bux or get nothing.

briannutter

It does appear odd to the average person why things aren't built around the o.e. At the same time you need to give shops and the aftermarket some credit. Much of what GM's designers learned to build the LS7 came from the aftermarket and running racing programs. Case in point, .9252 (the closest metric equivalent to .927) is standard in the LS7. LS7 rods are I beams btw. GM's 376 and 454 crate engines use .9252 pins and H beams as well. Unscrewing a set of LS7 rod "screws" and putting them down next to a set of ARP 7/16 bolts is pretty scary, but I commend the factory for making them only as big as necessary for their application.

There are many instances of the factory rod hanging in the for a mild 600 horsepower build. That being said, without a bushed small end, crappy bolts, and a big end that can't be resized for proper bearing crush...why bother? Most companies $500 H beams will handle 1200whp.

Back to the LS1/6: .945 isn't the answer. The engine should have been designed with 22mm pins to begin with. If .927 pins are handling 2300 horsepower today, why would GM use .945 for a sleepy 345 horsepower engine? They've learned a lot since then. Our little 6 cylinder 2JZ pistons withstand 183 whp per cylinder using a 22x2.500 pin before we swap to a thicker tool steel pin. Our 4g63 pistons run 22mm and handle 275whp per cylinder easily. Cup engines use sub .8268 pins at 830+hp. NHRA 500ci Pro Stock runs .927 pins. Why would I bother with something bigger? The answer is we don't; our latest Hemi stroker pistons utilize a 22mm pin (and matching rod) to make our ring lands .030" thicker than otherwise (which is huge). When the combined piston and pin and rod weight go down, the stress on the crank and block is reduced by tons (literally) at higher rpm.

The first LS engines modded in the late nineties were equipped with 6.125 sbc rods with the resulting .927 pin. Rod makers had them in stock and Piston makers had .927 pins in stock. Things snowballed from there into a huge number of combinations that benefit racers. You'll find that many of the aftermarket stroker kits for chevy, ford, chrysler etc. use a chevy rod journal, chevy pin, and chevy derived bore diameters. This makes for a wide selection of extremely good (and cheap) bearings, rings, and pins. The cranks and rods are smaller (lighter) than they would have been and hold up to whatever power is required of them. In addition, standardization means the aftermarket companies and engine builders can stock twice as many combinations and the volume drops the price 50% by the time it boils down to the racers.

jkkaz

JE and SRP are the same company. SRP is the off the shelf piston while JE is supposed to be the custom made pistons. In any case everybody makes a piston. They aren't as cheap, but they weren't that bad either. I had a custom set of pistons made for a Nissan turbo motor from JE. It ran about $800 bucks.

If it was me, I would just by a short block with forged pistons with or without a complete forged bottom end, depending on what your application is going to be.

wortex

That was our 1st try. Chevy does not really offer short blocks any longer. Either full long blocks or bare blocks. Thats what we used - Z06 spec LS6 block and it wasn't too bad either a little under a grand.
The 0.927 and 0.945 difference is not exactly for strength at all. The reason is that they went with a floating pin versus the press fit pin. The 0.945 is lighter then the factory 0.927 pin as they were able to make it thinner on the wall. The rod has a bronze bushing with oil grooves and a ring holds the pin. The LS1 and LS6 are totally different animals. The rod is very strong and the engine is more efficient then the LS1. Different piston, rod, etc.

Yes you are right about that the C5R program created the engines like LS7 and LS9 and they experimented a lot with new technology.
The trouble is the aftermarket industry didn't really follow that route. Sure you can build a strong engine but it will not be energy efficient and either it will be expensive or will not be capable of running for 100k miles.
No offense to the aftermarket guys but the factory engines are as strong as the "built" engines and they last a great deal more and cost half as much.
A built SB engine that puts out 500+ HP will be more money then a Z06 engine which will also run for 100k miles and be fuel efficient.
Big companies=big resources, direct fit and tested while small company=universal applications, lots of trial and error and you test on your own.
When I called the Mahle performance guys they could not come up with an answer for a simple question in a day. They have not had any experience with the LS6 engine at all. They had no idea that the LS6 used a floating pin for example.
I'm all for tuning and modifications but the aftermarket industry is still trying to push the SB chevy envelope when the last of the SB engine is over 12 y/o. a decade has passed on those engines and they still stuck with that.
I would not even want to imagine to improve on the LS7 or LS9 engine with aftermarket items. There is probably nothing available yet.

GM used the supercharger on the ZR1 and CTS-V so the factory pistons from that might fit the 6.2 engines but if you want to supercharge the 7.0 engine, no alternatives for the piston yet. With a Z06 high compression the supercharger isn't a good idea, also the cyl wall thickness is on the edge. Hence that GM went back to the 6.2 bore instead of the 7.0l

Both engines are good in their stock form but the supercharged in the ZR1 is a massive power.

anyway project is almost completed but GM farted on their conn rods, they sent us the replacement OEM rod without cracking them apart. So an another day or two delay due to this... somebody's *** should be whupped for that !

briannutter

I think you've come to the wrong website if you're trying to proclaim the factory engines can't be improved upon greatly. This board has thread after thread of blown up o.e. engines. Problem solved when they build up the engine with better parts. The O.E. concentrates on making every component in that engine to as cheap as it can be and get the job done for the horsepower the engine is rated for....no more. There isn't a single component that can't be improved upon in these engines by the aftermarket. Cranks, rods, pistons, cams, valvesprings, cylinder heads, rockers, intake manifolds, header, you name it...the aftermarket does it better. There are some aftermarket parts that belong in a LS hall of fame. Ever wonder why some guys in Memphis can design an intake manifold that kicks the crap out of an O.E. one? How about some cylinder head guys in Michigan, California, and Ohio making heads that flow 100 cfm better than LS1, LS6, L92, and LS7?

On the subject of O.E. designers being saints: They say a professional is somone that has spent 10000 hours at their craft. I've seen parts from every o.e. company where the designer obviously wasn't a specialist. Pistons on monday on and door handles tuesday. I know this because we build prototype pistons for some of the o.e.'s. We in the aftermarket see a very wide range of engine types every day, specialize in one component, and can apply the technology from one engine to the other.

On the piston subject...Why is it that the o.e. with all of their resources can't make a piston that doesn't slap when cold when we can make a forged piston quiet? Why did the LS motors suck oil like no tomorrow for years? Forged pistons with the coatings and the nitride Steel napier ring packs are vastly superior to what GM is using in their engines. Our standard pin weighs 105 grams and hold up to 1100whp with regularity before we start upgrading to the tool steels. Adding to the pin diameter adds to the rods mass and the width of the pistons pin towers (pure mass). The trick is to run the smallest diameter pin that has the required bearing area. Please enlighten us with your o.e. LS6's wrist-pin gram weight.

I'd like to tell you which American Aftermarket companies were chosen to do the rotating assembly components for GM's very own 376 and 454 crate engines, but I can't and I probably don't have to. The 454 makes 620 horsepower naturally aspirated, went through their validation process which amounts to beating on the engine to death for 50 hours, and comes with a warranty. The aftermarkets knowledge to build those parts came from working with the engine builders on this board.

I'm not sure if you've priced a LS7 or LS9 crate engine lately, but you'll see the vendors on this board making more power at 50 to 75% of the price and they did it 5 to 10 years sooner than GM did it. LS7's and LS9's are improved upon every day and LS6's are dinosaurs. If you think these engines are "efficient" it's only because horsepower requires fuel and the factory engines don't make much to begin with. Reliability?--Plenty of examples of people on this board who have been driving their 600 horsepower naturally aspirated and 900 horsepower boosted daily drivers for years.

WhiteRhino

iTrader: (6)

Brian, just wanted to Thank You for posting up. I like reading when the Pro's chime in. I run Wiseco's in my ls6 383 and think very highly of them. That's why I name drop you sometimes, even though i've never delt with you nor Wiseco personally. I just know you are very educated/experienced in the game. Also constantly improving the product with more lsx offerings.

bww3588

iTrader: (49)

i have mahle flat top with a 4cc valve releif, .945 pin on stock rods with a stock CD. i dont feel like doing the math, but i bet that would get you close to 9:1 with a stock cc head.