I have a 69 Camaro with a 94 LT1 engine and a Richmond 6 speed. At 3500 RPM and above there is a vibration, sitting still or driving. I picked up a used flywheel at a swap meet (small dia bolt pattern) had it resurfaced and installed a new clutch assembly. Is there a balance problem with the flywheel as in internal vs external incompatibility. I don't know what the flywheel came from and have not been able to find a listing for the casting number. Due to other circumstances I have changed engines ('88 350 to the LT1)and the vibration is still present. Any ideas?

Welcome to the best site on the web! graemlins/thumbsup.gif

I'm sorry to say that I can't really definitively help with your problem, but it sounds like you are on the right track. Maybe someone else can pop in here and help.

I don't also but when you are saying (small diameter bolt pattern) are you saying the flywheel had to be modified by making the bolt holes bigger?

Same problem, 2 motors, same tranny ? Did you also use the same flywheel?.... might have that checked/replaced.

One-piece rear seal 350's use a counterweighted (external balance) flywheel (with a neutral balancer). You should be able to see the cast-in offset weight on the forward face of the flywheel.

I've heard the 305 and 350 ballancing is just a touch different on the flywheel end, but i've never run into a problem with it..

late model iron flywheels have the following part numbers from GM for the 350"s follows...

12.75" is 14088650
the only thing i have at my fingertips is a casting number for the 14.0" flywheel that is 93433010N