I just had my 382 all bore motor done/installed. When i picked it up, it had already been run for awhile so i didn't notice anything. but the next morning, when i woke up to go to work, i heard this piston slapping sound. the motor was cold and it scared the **** out of me. i'm not used to it so i shut it off right away. now i talked to the installers and i was given a reason that because it was setup for such a large shot, that it might have been setup a bit loose. after starting it again later that day and letting it run, it seems to go away and i can't hear it anymore and will not hear it again until i let it sit a few hours(overnight). anyone got any suggestions or ideas on if this is really right? car runs fine after being warmed up. i'm still breaking in the spec stage 3i clutch, so i can't get on the car much either. almost has a supercharger whine when first started and at times makes me think something is wrong with the clutch setup as well. threw the belt on the dyno so i was offered an idea that the tensioner is going bad or is already shot and that could be the cause of the whine at initial startup in the morning.

Chris

 

anybody? i'm afraid to drive the car cause it's kinda embarassing and annoying

 

Dont worry even the stock ls1 had knock from the piston slap,some did and some didnt.what your builder did is alittle room for expansion. Thats the trade off sometimes.Some even run coatings on the skirts.

 

My forged 346 has piston slap in the morning too; after 5-10 minutes and warm up, it goes away. I didn't have any slap with the stock motor, so it scared me too at first. Now 17K miles later, I'm OK. FWIW.