how to tell if your vacuum advance is bad?????
 

i have a bad vacuum leak somewhere, it's making my truck run ****ty and my tranny isn't shifting, i got a new manifold new gaskets and i replaced the tranny modulator (this is a 307 sbc with a th350) and still i have the problem, i was adjusting my timing and i noticed on the back side of my vacuum advance there is a small hole and it will suck my finger to it, is it supposed to suck air in like that or is it a bad vacuum advance? i bought a new one already it was cheap so i decided what the hey, but i haven't put it on yet!!! does that sound normal the sucking in from the backside of the advance?????

yeah it was bad, i took it to the mechanic shop next to where i work and he put a vacuum gauge to it, and said it was wasted!!!!