Full throttle vacuum should not exceed 1.5 inches at WOT or the carb is to small and the motor will run lean at WOT because of excess vacuum signal at the boosters. Second you don't want more than about 38 degrees total timing at any time or you will get part throttle pinging as the timing over advances. Ported vacuum was done as an emissions measure to lean out the motor to help for smog reasons,and heres how you can tell what you have. I f you have a temp sensor on the top of the t'stat hosing and its hooked to 2 vacuum sources and goes to the distibutor on the 3rd vac line follow the 2 source vac lines to their source, those should be 1 ported and 1 manifold. It worked like this, if the engine was cold or at least not very hot it got ported vac timing, but if it got hot it got manifold vac timing to cool the engine down. This is how I hooked up my vacuum advance, got a Crane adjustable unit and set it for a max of 12 degrees and hooked it to manifold vac. Reworked the dizzy and set it for a max of 22 degrees mech advance. Set the total timing at 2500rpm for a max of 36 degrees from both sources. That means I'm setting at 2 degrees base timing, so it starts easy and then idles good as the vacuum advance comes on. This gives me the best part throttle crusing, no surging, and for whatever reason I get a little surge with 38 degrees timing so it stays at 36.
George
I'm saving my pennies for a MSD digital box and billet distributor, the timing retard feature for starting is so cool, you can run a locked distributor and still start the engine when its hot. Best of both worlds.
