[vector1]

I did an unexperimental analysis of with and without vacuum advance and figured it was worth 2 mpg. I am a believer in using it, quieter and snappy and can be easier on valves & exhaust. I had the carb tuned to run on the ragged edge of leanness at cruise, when I hooked up the vacuum advance I had to richen the transition slot at least one size, maybe two.