With gas going up Ive been looking for ways to get some MPG out of my dart.

What is better for milage. Ported or manifold vacuum going to the vac-advace on the dist? It seems to run the same no matter where I put it. With manifold vac i get ~10deg more right off the bat.

Manifold vacuum maxes out at idle and decreases when you open the throttle. Ported Vacuum increases as the throttle blade(s) open. Ported vacuum is better, with manifold vacuum you will lose your advance when you hit the gas.

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

I would think I would only loose it at WOT. At part throd I should still have some

You do, but the transition is strange. If you hook to ported vacuum, you get no vac. advance at idle and as you crack the throttle open the ported vacuum kicks in (drops out if you floor it). If you hook to manifold vacuum, its maximum at idle. Then when you step on the gas a little bit, it drops way off so the engine falls on its face, then recovers.

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Ported vacuum is the only way to get desired results from a vacuum advance feature. Ported is the way it was designed to work.

If you connect to manifold vacuum, you will have far too much advance at the bottom end of the rpm range. You may also have a hard time adjusting a vacuum pot that has reasonable response to the range of vacuum it would encounter since none where designed to work that way.

The manifold controlled advance curve would have maximum advance at idle thought part throttle and then fall off at mid to full throttle, that's just not the best setup.

It's ported for a reason, once you get it dialed in properly, you should get maximum results from this method.

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1980 Aspen 225 super six

as a matter of fact, manifold vacuum on the distributor would only render your mileage worse as your perfomance drops drastically too. You may achieve better power with no vac advance if your's a WOT car or a mid-modified car, but proted vac is the only way of actually getting mileage improvement out of vac advance feature.

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

A better question is: "how much ported vacuum advance will my engine take?"

The vacuum advance "pods" come with different amounts of advance, if you are after more mpg, try a pod with more advance. (11x or a 12x)
I have modified the arm of the pod to get even more light throttle total advance but there come a point where you start to get a lot of pinging which hurts mpg and your engine.
DD

If you want more advance than what your current pot can give you, order a vacuum advance can for a Feather Duster, that is what I did.

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

ok im back on ported.

I never really tuned a car for milage so that thing was normaly never hooked up in my other cars

actually if you did that (unhooking or not hooking vac pod properly) on a mild to stock engine you've been missing both performance AND mileage. For really taking advantage of not using vac pod (from a performance point of view) you really have to maximize your initial timing and limit the total mech timing and study the advance curve map closely along with your carburation, rear end ratio, engine specs, ignition type, compression ratio, type of fuel used, exhaust, vehicle weight, transmission used and gear ratio spread, and most important: your way of drive. say if you were using a 1920, 1945 or BBD carbureted slant with stock distributor and stock points or stock EI, stock or less than 200@050 cam (well, you get the picture) you've been driving with less performance and less mileage than what you'd have gotten provide that you should have had everything connected right and tuned right.

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

It was always connnected to ported on this stocker. I was talking about my other cars which where non-stock.

OK I'll stop my rant!

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.