I have a 1980 trans am with a 400 out of another trans am. Yesterday I finally got my car out of the shop. I got a new transmission, converter, and fly wheel put on so I decided to try it out. I punched it like 3 times in a row and noticed the converter did not make much of a difference and about 5 seconds after the last time i punched it i started to hear something like a deep Knock. It knocks more times the more gas i give it. it sounds like it is comming from the bottom could it be one of the mains broke or could it be the converter or flywheel is a little loose? if it is one of the mains about how much am i looking at to fix it?

 

i forgot to add when i parked it i left it running and the knocking went away so i turned it off. then i turned it on later and ran it for about 2 minuites and heard no knock. then when i turned it on 15 minuites later to go park it somewhere else it started knocking again so could it still be one of the manis broke ar somthing and is hitting the crank?

 

convertors dont make much of a difference if you dotn stall them up first...check and make sure all your bolts are tight and that the flywheel isnt cracked before you assume its the rods....how big of a stall did you put in it

 

i put a 2800 stall and it starst to get through the brakes around 2200. So you dont really think it is one of the mains holding the crankshaft tha broke or spun?

 

i put a 2800 stall and it starst to get through the brakes around 2200. So you dont really think it is one of the mains holding the crankshaft tha broke or spun because it does no knock all the time like i stated on my thread?

 

That knocking noise could very well be a bearing.... when you were punching it how high did you rev it?
Run it for 30 seconds, turn it off, and then drain the oil and see if there's little pieces of metal floating in it.. if there is... you're gonna need to rebuild.