Got a 73 Fastback with C6 and 351 Cleveland few months ago. The engine has a severe vibration. The seller said it was the driveline. He had no other information. I bought it knowing I had a problem. The vibration is in the engine or transmission. The vibration is present when the transmission is in neutral and Starts to get real bad above 1000 RPM. The vibration is the same as if you put an external balanced flywheel on an internal balanced engine. After several months of research I started to work. I approached the problem like somebody had put the wrong crank in the engine. The engine has a twenty eight ounce imbalance harmonic balancer and a twenty eight ounce imbalance flex plate. I made a weight identical to the one on the flexplate and tacked it on the flex palte opposite the factory weight on the flex plate. Vibration was worse. Then I cut the weight in half and welded it on either side of the flexplate weight. Vibration was worse. I have a new harmonic balancer to put on. Now I am going to try and slide the torque convertor back and run the engine like that. Are there any precautions to take witht the torque convertor to keep it away from the flexplate? Any other ideas to try?
Vibrates in neutral and gets sever as RPMs are increased.
Vibrates worse with weight welded opposite stock weight.
Vibrates worse with extra weight welded on either side of stock weight.
Any help would be greatly appreciated. Dying to drive the car to a Saturday Night Rod gathering.
Thanks for reading and for any advice. BBFan