I installed my old 12a into a fb I got and it makes a chattering when the car is in nuetral with the clutch out. The noises goes away when I push in the clutch.

I've used this engine in 2 other cars and it didnt happen. but when i installed it this time i broke off the bolt from the lower passenger side engine/transmission bolt. and maybe this is cuasing it?

Does anyone have any recommendations for what to do?

 

Maybe this thread will help you:

https://www.rx7club.com/forum/showth...=pilot+bearing

 

Throw-out bearing.

change the pilot bearing(bushing) while you're in there.

If that doesn't fix it, the tranny needs a rebuild.