Distributor vacuum - ClassicOldsmobile.com

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Distributor vacuum

Old March 29th, 2015, 03:56 PM
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Distributor vacuum

When hooking up the vacuum advance on an 83 H/O distributor what port do I use on the carb. Ported or full vacuum
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Old March 29th, 2015, 05:00 PM
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This has been a long discussed question and there really is no right answer. Try both and see which the engine likes better, going to manifold vacuum will require you to lower your curb idle setting once it's hooked to vacuum.
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Old March 30th, 2015, 07:43 AM
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Originally Posted by truckerlary View Post
When hooking up the vacuum advance on an 83 H/O distributor what port do I use on the carb. Ported or full vacuum
The original distributor in a 1983 H/O doesn't have a vacuum advance can. The CCC computer controls advance based on the MAP sensor and the TPS. I assume you have replaced the distributor? In that case, you'll need to experiment to find which source the car runs best on, manifold or ported.
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Old March 30th, 2015, 09:27 AM
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My high compression 403 had an aggressive cam and GREATLY preferred manifold vacuum.

Ported vacuum- retarded timing - low intake vacuum - can't idle, stumbles, stalls. Overheated while driving, overheated while idling.

I suspect the vacuum was so low the power piston was allowing the needles up and richening the mixture. It would idle at 1000, anything lower stumble and stall.

Changed to full vacuum to the distributor- major increase in manifold vacuum number, idles fine, starts easily [that advance is not there until AFTER the engine starts]. NO overheating even with the '85's stock old 307 radiator.

Your call. Whatever your engine likes.
has your engine been changed in any way from factory stock?
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Old March 30th, 2015, 04:49 PM
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To the best of my knowledge All that has been done is removal of all the computer controlled equipment. Items changed are the dist. to a vacuum advance GM hei model and a different quadrajet carb, not sure what it is supposed to fit and a performer Edelbrock manifold. Can't see much difference which ever way I hook up the vacuum
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