tuffluck

iTrader: (4)

ok, i searched for this answer, but did not find it. so, i am starting this thread, even though it seems that it *should* have, at least once, been discussed before.

anyway, i have been told by several ls1 owners that when an ls1 engine has piston slap, they have more horsepower/torque than the ls1's without the slap. the explanation:

"When a block is bored out at the factory, one "bit" is used per block. So... one"bit" is used to bore out all 8 cyl per block. The bore on the 1st cyl is almost always a "hair" bigger (we're talking .00X) than the others due to the new "bit". That is why piston slap, it seems, is always on cyl #1."

is this true? and if so, how much extra power are we looking at gaining here?

my car slaps on cold mornings, and so this is an interesting topic for me. my friend with a 340/360 (dyno numbers) ls1 drove my car and says it does feel a bit faster than many stock, so i dunno?

Got Me SOM

iTrader: (2)

I would think it would make less power cause its not sealing the rings as good therefore losing compression.

I'm just purely guessing I have no direct hands on experience.

There was a older guy here with a brand new nbm z28 that was running 11.2's consistently with just a lid, headers,converter,exhaust 12 bolt with 4.11's and 100 shot.
He told me when he heard that piston slap in that car he knew it was the right car for him.. I dunno.

skonka

I believe (but have not confirmed) piston slap can potentially reduce performance due to the knock sensors picking it up and retarding timing accordingly. A good friend of mine just traded in his 2001 Chevy 4 wheel drive with a 5.3 b/c it generated piston slap just out of warranty. Of course the dealer didn't want to do anything about it. He lives in VA and slowly determined that the truck didn't have as much power on hills and his gas economy was declining. I doubt it was the lack of compression, it was the ECM retarding the timing. I suppose LS-1 Edit can be used to compensate for such problems though...

tuffluck

iTrader: (4)

well, my piston slap, and most ls1 piston slap, only occurs when the engine is cold. when the engine warms to operating temperature, the slap is nonexistent. so the knock sensors picking up extra knock makes sense, but if the slap goes away at normal operating temp, then the knock sensors wouldn't be picking up anything abnormal at all.

Colonel

1. LS1s are sleeved. That shoots the #1 cylinder being "bored" first right out of the water.

2. Piston slap has nothing to do with the rings sealing. The rings aren't slapping.

3. Piston slap doesn't trigger the knock sensors even when the engine is cold.

I seriously doubt that piston slap has much, if any, effect on HP since it goes away before normal operating temperature.

35th SS

iTrader: (2)

I seriously doubt that too.thats kind of hard to believe.I have piston slap on the 35th when cold when normal goes away.

Rhode Island Red

iTrader: (2)

Colonel,

any proven way to eliminate the piston slap on LS1's I've got an early '02 that burns between 1-3 quarts of oil as well... seems like the only way would be to have the engine dismantled, and then blue-printed

as for the oil --- it's a GM car, so it's Normal so not even a miracle could cure this

Colonel

Don't worry about the slap. Just with LS1s I've had an '00, two '01s, and an '02 and they ALL have/had slap.

I would think that running a tighter piston to wall clearance would cure it but then that would cost you a little HP and efficiency as well.

The oil problem could be your PCV system (these LS1s are notorious for having this problem.) Thinner oil makes the problem worse. Check inside the lip of the intake manifold to see the evidence.

cantdrv65

iTrader: (3)

My 97 Lt1 and 92 Chevy truck both had piston slap as well as my 99 Ls1....The Lt1 had 85,000 miles when I got rid of it, the truck had 178,000 and my 99 Ls1 now has 108,000 along with quite a bit of nitrous use. My point is piston slap has nothing to do with performance or longevity of the engine.

goober35

iTrader: (1)

I would like to find out if they change the piston and rod design. If they where to make the rod longer and move the wrist pin up that would move the pivet point of the piston. That would cause piston slap. Just a thought but i dont know if they did.

Rhode Island Red

iTrader: (2)

colonel,

yup got the "puddle" of oil in the intake ... as far as I have heard, some people have done the ls6 valley pan mod with limited sucess... I guess the piston slap and oil should be considered 2 different things (my slap started around 5K so carbon buildup might be it)

as far as other ways to block the oil from the intake, I have not heard of any that did not mess with the crankcase pressure ...