Does anyone know if GM has cleared up their problem with cold start knock/piston slap with the current LS1 and LS6 engines? My 2001 2500HD 6.0L sounds like a diesel, and not just at cold start. Basically whenever it is idling. Off idle, the rest of the engine drivetrain noise masks the knocking, but it is still present. Of course, GM has told us all to go get bent because they're not admitting it is a problem. I love the thought of the new GTO, if not the exterior styling, but there is no way I'm going to dump another 30K+ into GM knocker. Did they finally start building these engines with the correct pistons? Thanks.

I guess I'm lucky, my '99 Firehawk has never had piston slap. The car has 23,000 on it and never noise from the engine.

Yeah, sounds like you are lucky. I've heard the Camaro/Firebird had the problem, as did the Corvette. I know they were changing pistons or rings in Corvettes for a while, but I think that was for an oil consumption problem, not the dreaded slap. It may have fixed both though, if they were changing pistons. Of course no such fix will be extended to the rest of us. Too many LS1 engines in the trucks and pony cars, it would hurt their profit/earnings reports...I would advise anyone who is going to buy a GTO to put their ear down near the wheel well after the car has just been started and listen for it. That is where I hear it best. Of course many people reported that their slap didn't show up until 10K-12K miles, so who knows. Sure wish I knew whether they have fixed this.

I'm sure they havnt changed anything for the 04 year. Not every LS1 does it but it is common.

30K more is a tad excessive, a stock displacement shortblock with great rods and pistons/rings can be had for less than $3,000.

GM doesnt recognize it as a problem and swears up and down that the engine is mechanicly sound. Maybe CNMT can shed some light, I know he was a GM tech.

I think you misunderstood my reference to $30K more. I meant there was no way I was going to ditch my truck and buy a GTO if the GTO engine is going to have the same problem. I agree about the engine replacement being about $3K. Actually, I figure if I keep the truck I'll try to get one of the Gen IV DOD 6.0L out of a junkyard in 5-10 years, so I can stop single handedly financing Chevron's pension fund.

It's only like 0.01% of pre 2001 LS1 that have had the piston slap problem.

Regardless of your .01% number, (I'd love to hear your source for this), I have it bad in my 2001 6.0L, and I don't want to buy another vehicle with this same problem. It is pretty common in the trucks, and I have heard complaints of it in camaros and vettes. I'll give you that on web forums you get a bunch of complainers, and a lot of the happy people may not ever post, but it seems a lot more common than .01%. I just want to know if the new pistons/rings they developed for the vettes have trickled down to all the other LS1's, since it sounds like they tried to address the issue with the new pistons. And of course, if the fix actually worked.

The monaros had that ls1 oil / piston slap problem. However I think thats been cleared up. No big complaints lately

Some of the GM engines do it, some don't, GM swears the engines are sound, because they are. Im a GM tech, and whenever we have that complaint come into the shop (mostly on the 6.0 liter trucks) we print off the bulletin information and give it to the customer. :D