[70 goat]

I got 2 question for you pontiac guys.

1. should the vacuum advance be hook up to ported or straight vacuum.

2. should the trans module be hook up to ported or straight vacuum.

The reason for the second question is the car at low RPM runs fine , but as soon as i raise the RPM it rev'es a little before it engages. Some what like a stall speed. But no stall speed in the car.And is there a difference in hooking up the vacuum advance to vacuum or ported vacuum. And why the car seem to run the same.Except for a high idle in park.

THANKS, DAVE

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[70 goat]

I got 2 question for you pontiac guys.

1. should the vacuum advance be hook up to ported or straight vacuum.

2. should the trans module be hook up to ported or straight vacuum.

The reason for the second question is the car at low RPM runs fine , but as soon as i raise the RPM it rev'es a little before it engages. Some what like a stall speed. But no stall speed in the car.And is there a difference in hooking up the vacuum advance to vacuum or ported vacuum. And why the car seem to run the same.Except for a high idle in park.

THANKS, DAVE

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[Ccass]

Reminds me of years ago when I took my 67 GTO into a Cottman shop because it was shifting poorly similar to what you mention. They quoted me $750 because the trans. was in such poor shape. I limped home and showed it to a buddy of mine and he moved the vacuum hookup and it shifted perfect from then on! I think that might be your problem.

[Blackcat]

Your answers are.
1. vacuum advance should be to the PORTED on the carb.
2. Vacume module on the trans should have full vacuum not ported.

Hooking the line to ported vacuum should effect gas millege and preformance. With full vacuum the car will idle at full vacuum advance. The car might be sluggesh. It will idle fine but the gas milage should be worse.

[70 goat]

Hey guys thanks for the info. Changed around the vacuum hoses every thing is great. The trans. shifts much better.


THANKS 70 Goat

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[Will]

The vacuum advance can be run from either manifold or ported vacuum, but it will depend on the engine. Low compression engines or engines with big cams tend to like LOT of initial advance and one way to get that is to run the vacuum advance to manifold vacuum. If you hook up a vacuum gauge and go drive around, first to a manifold vacuum source and then to a ported vacuum source you'll see that you have vacuum in your manifold at part-throttle cruise which is where your engine needs the vacuum advance. It may be more or less than the ported vacuum source depending on a number of factors.

In short, experiment with your timing to figure out what your engine likes best. Both of my cars like ported vacuum with high initial advance dialed in and a short mechanical curve, but high compression engines might have a hard time cranking over with a lot of initial advance dialed in so hooking them up to manifold vacuum is a good way to effect a "timing retard" until the engine is running. I know several engines that run real good like that.

As for the trans, definitely hook it up to manifold vacuum. That dropping out of gear you experience when it's hooked to ported vacuum is extremely hard on the tranny and chews your clutches up with all that engaging and disengaging.

[Todd]

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[This message has been edited by Todd (edited 07-18-2000).]