My '98 Z28 with 100K on it doesn't make much noise at idle when cold.

Remember guys, it's a GOOD think we audible piston slap (if you look at it right). If GM would have used iron blocks in their GenIII motors, we wouldn't have this issue. Being the block is the single heaviest piece on our car, I'd gladly take an Aluminum one. Very few cars in this price range have an Al block.

Even though grey cast iron blocks are quieter, I'd still choose the aluminum block for its lighter weight. Very few LS1 cars make enough power (taking a lot of them into consideration here) to warrant a heavier, more rigid, steel block.

I'd agree with the theory Abe pointed out, that being, if aluminum expands at a different rate than iron, the pistons need a while to expand to within tolerance in the bores. This is also the same reason you don't want to go WOT on a super/turbocharged car right after start up... unless you like building motors.

My friend mwill15 has a 2001 SS with a diesel in it (49K miles). EngineerMike's dad has been seen driving a rattle-free, mint, '02 Firebird that also has an appreciable amount of slap. Saying that the '01 & '02 cars have no piston slap issue is a misnomer.

Ben T.

 

Why use aluminum blocks with iron pistons? LT1's have aluminum pistons, so why not use aluminum pistons with the LS1 aluminum block? wouldn't that eliminate the slap?

 

4-20-05 frist day of ownership
69,200 No Slap
11-20-05 Last Day I drove/start'd it, In storage for Winter
78000'ish No Slap

Also it burns about 1/3 or 1/4 a Quart Ever 8k on AMSOil 5-30 with PF59 Filter or K&N Filter

FYI - Issues i have had with my 98
Wire and Plugs - Fix Missfire in Cyl #4 (Lookd factory)
Replaced Dif Seal and Fluid( was Seapage and fluid didnt look good to me)
Fuel Filter was VARY OLD i couldnt blow though it
and Roters and Pads
Front Trun Single Housing and Pig tall replament(water Dmg)
Are the only Issues i have run into with my 98 T/A

 

No one is using an iron piston. There are iron sleeves in the aluminum blocks. The aluminum blocks accentuate the ticking/slapping noise more than the LT1's iron block did.

Ben T.

 

ok so the iron sleeves are what aren't expanding as fast as the block, that makes more sense, cause i figured LS1's couldn't have iron pistons, that would be stupid.

 

I have chrome pistons. And I'm a post *****.

Abe

 

I've heard plenty of iron block engines w/piston slap, either from forged pistons and the additional clearance they require, or from engines with excessive bore wear.

Actually the cause of the slap issue on LS1s is the pistons. Older engines used pistons with a steel insert. LS1 pistons don't have the steel slipper... lighter weight, quicker acceleration. But they expand more so they had to increase the clearance a bit. Most engines are still quiet, but those unlucky few who have a block with the bores at the max allowable bore size + pistons at the minimum allowable size have extra clearance... and the noise that results.

 

Really old engines had iron pistons. And some Vega engines had iron plated pistons that rode directly in silicon aluminum bore. And it was a stupid idea cause those engines sucked huge.

 

54k

 

Almost 44,000. And chrome pistons dammit!

Abe

 

My 98 has some slight piston slap, and I'm at 54K. It don't bother me at all, goes away after just a few minutes, and runs great!

 

50k and no slap. What does piston slap even sound like?

 

02 Z28 No slap 46,000K M6

 

my 99 trans am is fun but sucks

90k miles, no piston slap, crappy power (for a t/a that is) i think any other 4th gen on the road would beat me maybe even lt1's

so no piston slap no oil loss but plenty of other funny noises and small probs

that being said.... it'll do me just fine till i get a vette

thats what they're for right?

 

Wifes 98 SS, no piston slap, no oil consumption, 30,000 miles.

My 2000 Formy, light piston slap just for 20 or 30 seconds on cold starts, no oil consumption, 24,000 miles with the last 3 years being a trailered race car.