Well about 3 months ago I stated getting a little piston slap...at least that's what I think it is? Only on a cold start and only until temps come up to say ~ 150*. It's a horrible knocking sound that will get louder if I roll on the throttle.
Oil pressure is good, M1 changed every ~3000 miles. Sound about normal? It didn't start after any incident or race or anything like that, it just started doing it.
I have 33K miles on this engine.

 

Mine sounds like its got some slap in it and I've only got 2*,000 miles on it.

It sucks but I'm not seeing any performance drops or anything like that. Stupid "normal" gm problems

 

Do you run a catch can with your FI setup? If I recall, this so called "piston slap" would occur in vettes where the owners drove them like grannies and the blowby from the low tension oil rings would cause buildup on top of the pistons. This would make the carbon on top of the piston smack into the surface of the cylinder head. This is why sometimes GM top end cleaner will make it go away. If you don't run a catch can in your setup, I can see where high levels of blowby would cause buildup in your intake ports and your pistons. I doubt this is it but it's a possibility. I run a catch can even on my NA 6L and every oil change (2K miles) I dump about 2-3 table spoons of oil out of it.

 

Normal.

 

Hmm, I would think with the amount of Meth I run that I'd have little build-up on the piston, valves or anything else for that matter but I don't run a catch can and no doubt there is some truth in that.
AK: do you have the same issue? What I do is just drive as easy as possible until the engine reaches normal operating temps. Maybe I will try some GM top end cleaner too.

 

try seafoaming it?? get it on video tape

 

Cold start piston slap is actually a pretty common thing for these trucks when it's cold out. Mine only does it when it reaches freezing temps.

 

Normal! last winter I took mine into the dealer for them to check it out,they told me it was because the high nickel content of the block,I Said OOOOOOOOOOOOOooooooooKaaaay! believed every word! then bought my wife a TBSS and it does the same thing!Now I call BS! but I have talked and listen to others and all have same issues,It just happens.I will be pissed if it happens to the LSX.Lol!

 

It's not as cold here as other parts of the country, it's like high 40's or low 50's in the am. Sea foam huh.... smoke show!

 

sorry trever its a rod bearing.