Because they had info online on how to add ported vacuum to a 97 before they started making them that way.
or you could just tap in to the intake manifold and run manifold vacuum.
Yep, I just did that in my truck to get more timing at idle. So far it's working great.
You need to make sure that the vacuum advance kicks in below whatever vacuum you have idling in gear (if automatic), and make sure that your total timing is good.
I can go into more detail if there's interest.
OK, so what am I missing here? If you have all the vacuum advance "in" at an idle, when the motor's vacuum is at its highest point, when you step on the throttle, and the vacuum drops, won't you get a decrease in the ignition timing at a point the timing should be advancing?
A ported vacuum has little vacuum at idle, and as the throttle opens, the vacuum increases, which causes the vacuum advance to advance the ignition timing, as it was intended to do.
Have things changed since I was in auto classes in the early 70s? Gene
