Its a trial and error thing. Compression can make the engine ping with to much timing, so depending on how much mechanical advance yours has, you will have to adjust according. Each HEI is a little different when it comes to advancing, some just keep going, some come in quick, some very slow, there is a endless combination of springs and weights to choose from.
Total timing can vary from 32 to 36 degrees, again it depends on how your engine responds. Its pretty easy to change, so try a few different settings and see how it runs. Full throttle short blasts will tell you a lot, also long hills where you can work the engine are helpfull. Ideal timing is where the engine has very slight ping when working up a hill at medium throttle, the ping should go away if you step down enough to open the power circuit in the carb and drop a little vacuum. New cars run right on this edge all the time thanks to the computers and constant adjusting.
Joe
