I have an 86 TA with 305 HO Crate engine (with rollers etc, cant understand why they bought 305 but not 350 but thats another story).

When I bought this car in 1998 I heard a strange sound (klonk klonk) right after I started it up (cold) but it did go away in few seconds. If I start it and the engine is hot then you cant here any noise.

First I was worried but after when it did not increase, and nothing happened I stopped to think about it. Finally I decided it must be a piston slap.

Few days ago a friend told me he thought the flexplate was not like it should be. If its so I would think this sound would alwais be when the engine is running but not only right after startup.

Other than that the engine works very well (but will be replaced when my 406 is ready ).

So to sum it up, the sound is only when I start the engine and its cold, disapeares in few seconds, and does not exists if I start the engine Hot.

Thanks, Jon H.

 

 

Flex plates don't change according to temperature; so it's safe to say it's not that.

If it goes away within a very few seconds, like less than 5, it's probably a loose main or rod bearing.

 

check your starter bolts, when i had my 88 firebird one of the bolts broke off so it was hanging on by one of the bolts. it would grind sometimes,as well as clunk, because the starter was not ligned up right and and loose. then one night it started making scraping noises cause it was rubbing on the flex plate (luckily on the way home) and the last bolt finally came loose and the starter was resting on my exhaust. so that could be your problem. Good luck.

Robert

 

Thank you all, I will chech all those things