Bob1320

My 2002 LS1 with just 400 miles on the odometer has moderate piston slap when the engine is cold (under 200 degrees, water temp) through the RPM range of 1500 to 2000 RPM in each gear (6-spd manual).

I find it unusual for a car costing almost $50,000.00 to exhibit such a problem. I am a certified mechanic and engine builder. Piston slap is not caused by barrel-shaped pistons as I have seen rumored here. No matter what the piston design is, this noise is caused by excessive clearance between the cylinder wall and the piston skirt. This can also lead to excessive oil usage because the piston is rocking in the bore. I have built many race engines with forged pistons with up to .006" piston to wall clearance and none had piston slap. Even my '65 327-365 HP Vette that runs 12.20's is not noisy. So, it's something you shouldn't have to put up, even with a high performance engine.

The GM listed spec for piston to cylinder bore clearance for the LS1 is .0007" (Minimum) to .00212" (Maximum). It doesn't sound logical to me, that if the clearance is held to this spec, that piston slap can exist. What is really going on here GM? For such an exotic car, there shouldn't be ANY engine noise. This is my 8th Corvette and I love this car, but I hate the noise.


[Modified by Bob1320, 9:21 PM 11/30/2001]


[Modified by Bob1320, 9:37 PM 11/30/2001]

BOBSZ06

When I got my Z06 in early Feb this year, I noticed some piston slap under cold engine conditions and in the revs that you mentioned. Well now with over 6k miles on her and having fully checked out the rev limiter several times, I can say that the engine no longer has any piston slap. So, I would not get too discouraged at this point, but give it some time and you may find it disappears as it did in mine. Mine sounded like a diesel engine at 2200 rpms taking off when it was cold, but that no longer is the case! :D

vettenuts

There was a piston change to correct this in 2002, but the first couple of weeks of production got the older piston. Do you know the build date?

My build date was 29 October and the motor is totally quiet when cold. My wife's Pontiac, on the other hand, has slapped since new. Has almost 100K on the clock now without a problem. I agree, for the price of the car this should not happen.

Gary2KC5

when dealer measured my tollerance they found the piston clearance was .004 so they bored 1 over and put in hand fitted pistons.

also, you might find this article interesting:
http://www.c5registry.com./2k2z06/page5.htm

looks like you should get yourself in line for a new set of polymer coated pistions.

Pepper

I remember having an 11:1 compresssion (forged piston), solid lifter, 7200 rpm Chevy monster when I was in high school in the late 60's.

My '76 Triumph motorcycle sounds like the incredible machine but there's nothing wrong with it. I made the mistake on an earlier Bonne to do a top end job to eliminate the piston slap......the overheating that resulted from the topend job was much worse than the normal ***** of the slap!

We don't know what engine noise is now-a-days. Personally I like machine noise.

zoomnz

[QUOTE]when dealer measured my tollerance they found the piston clearance was .004 so they bored 1 over and put in hand fitted pistons.

Gary2KC5
What did you have to do or go through to get GM to check piston wall clearance? Did they have to remove the engine?? Were you burning a good amount of oil?? Thanks..

ZOOMNZ

ZO6LS6

The new style coated pistons to remove reduce slap, were started in April '01.......
THis is for LS 6 engines.....I do not know about 1's///////////

vettenuts

I know the LS1 also got the piston, but am not sure when. At a minimum it was when they got the rings which was early 02 production. But now that you mention it, I think the LS1 got the piston's last spring also.

ZO6LS6

vettenuts........correct.......the rings were not available until AFTER the the intro of the '02's.........a couple of months after.....I believe they have not, were ot available until just recently............... :(

vettenuts

According to the article I read, the rings went into the LS1 in the first couple of weeks of 02 production. Do you have better information?