I have searched for other threads on various engine noises, but I can't find anything that compares to a "noise" I am getting. At partial throttle not under high load typically between 2 to 3000 rpm I am hearing what sounds like a slapping noise. It gets louder once the engine is up to operating temp. and goes away when I put more load on the engine. It may be I just can't hear it when the exhaust note is higher (I have a LM). I have read that the CAI could cause this, but that doesn't make sense. I thought the plastic shield in front of the CAI might cause this so I secured it with bolts through the shield and CAI....but no difference. The car runs strong but would really like to get rid of this annoying sound....it kinda takes some of the joy dropping the top. Any help?
Thanks, Randy Hughes

 

Anybody with suggestions would be appreciated...
Thanks.

 

BLUEBYU:

I sincerely hope this is not the case with you, but I have a friend with a 98 SS with low miles. And in 2001 his LS-1 developed a sound that sounds simular to yours. The sound started out like yours but soon got so bad you could hear it from up the road.
What had happened is his oil pump when out and was not aware of it. The result was the excessive heat caused some of the valves to warp and it was scraping away at the aluminum cylidner head, causing little aluminum flakes to get all in his engine. It ruined the heads and pistons.
I hope your problem is not as serious as this but you may want to have your oil and water pump checked out.
I have also known other people with a simular sound, there issue was that one of the pistons was actually hitting the spark plug at TDC.
I really doubt this is your case, but I am just trying to help.