[AdamIsAdam]

Originally Posted by nytrainer

Maybe I'm reading this wrong Adam but it seems you are calculating/adjusting total timing using vacuum advance? Initial and mechanical advance combined (with no vacuum advance factored in at all) will give you your total advance (for ex. 34* total with 12*initial & 22*mechanical). Springs will dictate how soon/fast in the rpm range the mechanical advance comes in (you should be OK as Richie said curve was good). The vacuum canister will further advance the timing at cruise with high vacuum signal or idle when connected to MVA as you have. This will help with engine cooling at idle and cruise (benefit to oil pressure too). The need for the adjustable vacuum canister is to compensate for your cam's profile that gives you a lower max. vacuum than stock type cams. Your lower max vacuum signal may not be high enough to actuate a stock vacuum canister.
Maybe you do have a handle on this concept and I read it wrong but just trying to help.

Maybe I wrote it wrong, but I do understand that the vacuum advance doesn't come into the total advance formula. These figures were all taken with the vacuum advance disconnected: 12* initial, 32* total at 2,800 RPM and about 20* at 1,800.

When I said that it idles at 12* initial, then I got it up to 36* by connecting the Crane advance, that was all at idle. The car likes to idle at 36*. That means that part throttle cruising maybe be as much as 58* or so. They say 54-56* is ideal for efficiency on the higway (that's mechanical + vacuum at part throttle like highway cruising at 3,000 PRM.) Maybe 58* is too much and giving me the surge. I'll go back and double check my Crane notch plate limiter and start that process again.