[geeteeohguy]

Originally Posted by 64speed

My machinist is a hardcore racer and I don’t think MPG ever enter his mind

This is concerning. Your car is a street car. The only cars that run locked in timing with no vacuum advance that I know of are drag cars. If your initial timing is 27, be prepared to knock the nose off your starter and break flywheel teeth on a hot start if you have ignition connected.

ALL street driven cars should run vacuum advance for fuel economy, power, engine cooling, and overall performance.

How much and manifold or ported depends on what your engine wants.

Optimal timing can't be determined on a run-in stand. Your machinist is blowing smoke.