Thrust washer
I used to dirt track race a 455 olds motor and the only weak point I could find was the oiling system to the cam and the thrust washer at the rear of the cam. It pushed out just enough to affect the timing under load but would idle perfect. When I tore it down I found that when torque was applied the cam walked backwards and when at idle it would pull forward with the chain. If you rebuild it there are better replacement parts if you plan to race it.