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Old 09-11-2003, 10:32 AM
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LOL, well, thats kinda like trying to talk politics with 10 different guys. Once you get past having an all stock engine, timing and how to get timing at different rpms is a matter of what works.

As a rule of thumb, vacuum advances use ported vacuum. Thats the port that is above the throttle plate. It only comes on when the throttle plate is opened.

BUT,,, a few car makers also used maifold vacuum at idle. Its best to ck your manual for the original hose routing for your specific make and model.

Having said that, advance vacuum can also be hooked to a "manifold" vacuum source. That will give you more advance at idle, often helping the idle quality and aid in a little higher idle speed and enhanced cooling at idle.

Ford and Chevy used to use a thermal vacuum switch for changing the vacuum source going to the dist. At cold and normal eng. water temps, the dist. got ported vacuum. At very high water temps, the dist. got manifold vacuum to speed up the engine at idle to try to keep cooling efeciency better. I always remembered how to hook them up by remembering the word "C.A.M." . Top port went to the "carb" vacuum, middle port went to the "advance", buttom port went to "manifold" vacumm.

From what I've read, the best place to start is un-hook the vac advance and set the TOTAL combined initial and machanical advance to 34 degrees at around 2500rpm. Then hook up the vacuum advance to ported vacuum and drive it and ck for pinging and performance. You can buy an adjustable vacuum advance for most apps. and make small changes in the amount of vacuum advance you get under acceleration.

Personally, for my engine, I find that in the winter times, I run my inital advance 4 degrees above what the engine decal states. ( its cooler and doesn't ping.), but in the summer I have to drop it down to the stated setting or a couple degrees lower, depending on how crappy the gas is that year! LOL


With all that said..............LOL...........There will probably be 10 more posts made telling me I'm wrong, but I expect that too, as everyone has had positive or negative experiences with different ways to do it. Once you get past stock, its whatever works. But you need to start someplace.

Mark