do not ckeck with vacum advances run the timing up to where it stops and lock it down at 35 to38 timing .when this is done check vacum pull it could be as much as 47to50 on pull .i do not use vacum advances for a engine like yours and bigger .i lock it and put more on crank and go with the lite springs if you use the vacum pull check to see if it s ported vacum or not you will need ported this will not pull at idle