Small Block & Big Block Chevy Specific - need help with timing motor

Ive been trying to set my timing but when i try to the timing mark just jumps around on me i cant tell where it needs to be ive also tried to bring up the idle a little bit but when it starts to mellow out it starts to advance my weights, i just advanced it untill it started running good so i could break in the cam and now i keep advancing it just a little twist of the dis. at a time and the motor just keeps pulling harder and harder, but i would like to be able to se where im am on timing, also my cam is 507-510 lift 240-246 dur 110 lsa i have heard of people not running the vacume advance with larger cams should i or should i not run it, thanks alot

Ryan

Set total timing, we never even check timing at idle. Just my opinion.

Ive never set my timing that way how would i go about doing it?

Unhook vacuum advance from distributor and plug it. Rev engine to 3000ish rpm and check timing. Try to get 34-38 degrees at 3000ish rpm. Tighten down the distributor. With a bigger cam I would run the vacuum advance on full manifold vacuum. After setting total timing to specs above now hook up the vacuum advance and adjust it such that you have around 50 degrees of advance max at 3000ish rpm. Being on full vacuum will smooth the idle and help a little with low end throttle response.

I always set my timing at 10-12* initial first (at idle w/vac advance unhooked & plugged), then have 34-36* all in by 3000rpm. I like to use between 10-14* of vac advance (adjustable cans are nice) and plug into manifold vaccum. This will give you 20-22* at idle with the vac advance hooked up and will improve your idle quality & throttle response along with making sure your carb stays in the idle circuit.