that's 14mpg highway, at constant speed. it gets considerably worse when the right foot comes into play (6 to 8 mpg mixed street/racetrack).

What makes me think about the vacuum advance is the overheating at idle that I'm experiencing.

I'm using 98 octane fuel (or 95 in backroad gas stations, sometimes they don't have a 98 pump). I have a fairly low comp ratio (9.3:1), as I planned the engine build thinking of future enhancements...

You think I could have detonation at 2KRPM when the engine is loaded if full advance is there?
Maybe I just need a street distributor with vacuum advance then - I just read an article someone posted today about that.