My friend had a 55 Chevy 235 car engine in his 51 truck. He told me he was driving it not sure how aggressive but he heard a loud bang on his motor and it shut down shut it down. I bought the motor from him for parts and it had a fiber gear and hydralic lifters. When I took the motor apart the teeth were completely worn down on the cam gear, a couple of lifters the spring clips were off and there was two pieces at different locations on the counter weights on the crank had been worn down. The bearings were ok.

http://i1291.photobucket.com/albums...20Engine/55fibergearpic2_zps77409944.jpg

http://i1291.photobucket.com/albums...unterweightby3pistonpic2_zpsc0bbd59e.jpg

Maybe just a wire came off somewhere but if you pull it apart take a good look.

"As I lay rubber down the street, I pray for traction I can keep, but if I spin and begin to slide, please dear God protect my sweet ride." -Amen

56 Chevy 3100