Reply to "Total advance, please chime in"

factors:

>Cylinders heads (combustion chamber design)
>Camshaft (when the intake valve closes)
>Fuel octane
>Piston design (flat top, domed top, dished top)
>Intake manifold design
>Fuel/air mixture (consistency, distribution, ratio)
>Spark quality and cylinder to cylinder consistency

What I can tell you, back in the 1970s & 1980s, when I worked on other people's cars (including engines), I set-up 351C engines with 36 to 38 degrees total advance, all in by 2800 to 3200 rpm. This was as per Ford literature. The engines were equipped with factory iron heads (both quench & open chamber). Back then the only alloy or aftermarket heads were those sold by Ford SVO, and they had exactly the same combustion chambers as the iron heads.

I set static compression in the range of 10:1 with the goal of achieving 7.7:1 dynamic compression ratio (cams tended to have a bit more advertised duration back then). The gasoline was California pump gas, rated 91/92 octane; that was the highest octane pump gas available. I used Ford distributors curved by a local shop I had close relations with, 20 degrees centrifugal advance by 3000 was our goal; their work was precise and reliable. Obviously 16 to 18 degrees static (initial) advance. The vacuum advance was connected to ported vacuum. The engines were equipped with one of 3 possible choices in intake manifolds: OEM iron manifolds, Ford aluminum dual plane manifolds, or Shelby/Blue Thunder manifolds. The carbs were either Motorcraft 4300D modified by a local shop, or over the "Ford Parts Counter" Holley carburetors designed for the 429 SCJ (780 cfm vacuum secondary). The calibration of those carburetors was smog legal, these engines were daily drivers and had to pass California emissions testing of that era. Even the guys into drag racing drove their cars to work.

I don't think my information necessarily applies to you, but I hope to make the point that the appropriate ignition spec will depend upon all the possible variables. I agree with Brian (bdud) to follow the advice of the engine builder. They had their reasons for stipulating the limits they made.