Distributor setups for L78 or L72 engines?

[@wot]

The vacuum advance unit is non adjustable an adds 15 degrees to the mechanical advance on a stock L78, yielding 51 total timing. If you are positive there is no detonation, check the plugs to confirm, leave it alone. If it is high speed detonation, back off the timing a couple of degrees. If you detonate under load, its probably the too much vacuum advance. There is NO vacuum advance at full throttle, engine vacuum will be close to zero.