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?

 

Normal troubleshooting should be posted in a Generation Spacific Forum. Transfering to Classic Tech, thanks.