My timing jumped quite a bit and the oil pump (spins freely) and distributor (gear and pin still good) are ok and yes the distributor was clamped down well.. My father and I put put a new timing chain and gear on in March. Does anyone have anymore ideas as to what would cause the timing to jump 15-20* and hold that far off? Thanks in advance.

 

If you have a mag pickup ignition ,Did you swap to a new ignition module?
If the polaritiy is reversed the timing will be retarded by about that amount.

Then if you fix the polaritiy and the base timing will advance by the same amount.

 

If the engine still runs about the same,,, check dampner to see if ring slipped.