This discussion would help me too, it seems my car was somewhat retarded on overall timing as exhaust/crossover paint is significantly burnt from new and was running hot.
I'm not sure my timing mark on the balancer is correct so I am going to confirm that soon (with degree wheel and piston stop and careful rotations).
Regardless, I'm running 110 octane right now to start on the safe side and once I know for sure how the engine (presumed stock rebuild) is configured I'll back that down.
Car runs well and cooler and doesn't ping and nice performance at 18 degrees base (if balancer mark is correct). It appears that I am getting about 10 degrees mechanical advance and about 10 degrees (from manifold) vacuum advance for a total of about 38 at 3000 just sitting still, as I held rpms around 3000 just sitting in the garage with no load and dialed back timing light on that. But when folks are saying "Pontiacs like around 32-34 degrees" I have always assumed that is only base+mechanical. So do I need to tear into my distributor to see if they have welded/limited the mechanical advance to only 10 degrees (measured at the balancer with a dial-back timing light)? Would you be expecting to see as much as 20 degrees (at the balancer) added from mechanical advance alone by 3000 rpm, to be added to a 12-14 degrees base timing to achieve the "Pontiacs like 32-34 degrees" total, assuming WOT at that point meaning zero vacuum advance?
Thanks!
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