NOS327

iTrader: (30)

Granted this example picture is a 4.125 stroke build in an LS3 block (credit Dietcoke here and yellowbullet), but I've heard from several people that skirt wear is tremendous on 4" stroke builds. Some say this brand piston or that brand piston do better, but each time I talk to the next credible source, it contradicts the previous piece of data I picked up.



So is it a crap shoot, or matter of machine work (piston to bore fitment), or prep on lower cylinder wall/sleeve (polish/radius high load side of sleeve), or are some brands of pistons worse off than others, coating/no coating?

I'm basically looking for representations of engines with 4" stroke that you've taken back apart. If it looks particularly good or bad, what did (or didn't) you do?

Thanks,
TJ

RX-Ben

iTrader: (7)

My understanding is that any 4" stroke piston will have some wear.
Chamfer the bottom of the sleeves.
Proper thing is longer sleeves that fully support the pistons at the bottom of the stroke.

Jimbo1367

This is why some suggest no more than a 4.0" stroke.

Unreal

My factory LS7 pistons showed no signs of wear and that is a 4.0" stroke motor.

DietCoke

iTrader: (18)

LS7 sleeves are longer then LS3 sleeves, so you can't really compare the two.

In reference to the above pics, it was the opinion of the local machine shop that piston to wall was setup too loose in the engine originally, which caused that excess thrust wear.

RX-Ben

iTrader: (7)

You will still see the wear on engines with proper build specs. Sleeves reduce it and prevent the cylinder walls from venting out the side of the block (like LS7s are known to do).

Jimbo1367

Dietcoke,
Don't bother saying TSP had anything to do with this. They will chastise you.

silver2010

Please explain what that means.

silver2010

About the sleeve side venting.

RX-Ben

iTrader: (7)

The piston putting a hole through the sleeve, out the side of the block.

silver2010

Thanks for the answer.
OUCH that would be.

DietCoke

iTrader: (18)

That wasn't meant to be implied at all. This wear was somewhat expected when I built the engine, the machinist simply felt that a tighter P/W could have reduced it somewhat. TSP wanted to do a 418 and not the 429 for my goals originally, and this is why. There was no problem with the shortblock at all, it's just a product of the combination. Hope to get at least two seasons out of the refresh, then I'm going to sleeve it BIG and do something else.

A.R. Shale Targa

iTrader: (2)

Forged pistons need a .0045"-.0055" piston to wall clearance because of the
alloy's expansion rate.....this causes more piston rock. The 4" arm obviously
increases rod angularity which increases piston speed and side load. The
shorter sleeves will contribute to wear during directional change @ BDC, but
slight amounts of detonation @ TDC will **** the slug and wear it more on
the lifter valley side than the exhaust side. If your tune was on the ragged
edge for max power the 4 that are worn more could have been slightly leaner
or burning a bit hotter. As piston rings wear after more use/abuse; oil contam
ination also contributes to detonation......plenty of factors

briannutter

Hey there, the pic of that set of pistons looks pretty bad, but I need to see more. Please send me additional photos to bnutter@wiseco.com Also details of the build and which block was used, how much time was on the motor, any dial bore guage measurements your local machine shop was able to get, if you see a part number pin stamped into the piston tops, unexpected noise on startup, etc. Any ideas you may have on what happened are welcome.

To answer the general question, the blocks have different sleeve lengths. They should all be good for 4" with the iron blocks having the shortest cylinders I'm aware of. Chamfering the bottom of the blocks is tricky and some of the engine builders will sand and radius the bottom of the sleeves. Because the mains are close to the bottom of the sleeves, it's pretty easy to get tight spots at the bottom of the bore when honing. Lastly, going overboard with rod bolt clearancing doesn't help. We've developed skirt successful profiles for 4.250 in a LS7 and other aftermarket blocks with longer than stock sleeves with the math being pretty straightforward. We have a lot of top notch engine builders on this board with a lot of experience with this, so we'll take a look at those parts and see if we can get you an answer.

Thanks, Brian Nutter

DietCoke

iTrader: (18)

Brian I will send you all the pictures I have and measurements thursday, once I have access to my home pc and the data.

Jason 98 TA

iTrader: (4)

Dietcoke I have the build sheet on your engine here if you'd like to see it. Piston to wall was setup at .004" on your build. The extra long stroke does like to wear more on pistons than the 4" setups.
LS3 blocks don't have long sleeves so the longer stroke puts a little more wear on the pistons. LS3/l92 blocks also like to wave the sleeves because they're pretty thin. The bad thing is LSx blocks will solve that stuff, but you just hate to run a heavy block in a already heavy 2010 car.

We do now offer the LSA blocks that are definitely stronger sleeves, but they do cost more $$$$ from GM
If you'd like a copy of the build sheet let me know!

Jason

DietCoke

iTrader: (18)

Jason I got a copy from Aaron, just to send to the wiseco guy. I didn't create this thread, I was expecting the wear, if not so pronounced so soon. Hopefully I can get another season or two out of the motor and then its time for some sleeves and BIG inches.

Jontall

So you're saying that a LSX block is better for a long stroke. Would Darton sleeves in a LS3 fix the problem too?

DietCoke

iTrader: (18)

Just want to make a note that out of the blue, wiseco offered to make me another set of pistons, with a new skirt profile they came up with to see if it helps with the wear, custom, for the new honed bore. I was blown away, as they contacted ME. Big thanks to Brian Nutter @ wiseco

DaFireMan

iTrader: (5)

It is pretty cool that they gave you a set of pistons! They just made me a customer!