Hook Up Vac Advance? - Team Camaro Tech
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post #1 of 5 (permalink) Old May 9th, 02, 06:31 PM Thread Starter
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Join Date: Feb 2002
Location: Pearl, Mississippi
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I noticed that the vac advance hose (the one coming from the bottom of the distributer, going to the front of the carb) was missing on a fellow CAMAROs.net tech team members engine. Is this proper? My mechanic told me to do away with the hose, but I refused! The Idle changes when the hose is off, the lope is definitely evident!!! now where this may sound good to the ear, is the engines performance hurt by doing this?

I am asking because it has always been mt experience to keep it hooked up... it makes a lot of diference on the street VS, the track right?

With that being said, if I unhook it on the track, will my car run better(better = faster/harder/stronger)? And if I hook it up on the street, will it Perform decently? (decently = fuel economy/drivability/response)

Thanks - Jerry

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post #2 of 5 (permalink) Old May 9th, 02, 11:39 PM
Join Date: May 2002
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If you want to leave it off that is fine, but you will need to make other adjustments to compensate. First you initial timing will need to be increased to compensate for what the vacum advance is currently doing. (that is why you see the change in idle with out it)
Secondly you may need to change to lighter springs on the centrifical advance. This will allow the timeing to advance quicker w/o the assistance of the vacum advance.
Good luck
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post #3 of 5 (permalink) Old May 10th, 02, 03:37 AM
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Vacuum advance will do absolutely nothing at the track, hooked up or not. It will help on the street with mileage and drivabillity. That is all there is to it.

You can hook it up to ported vacuum where there is no vacuum at idle as the factory did or hook it up to manifold vacuum as was done before emissions but the can should be different or modified for that application.

Curve the distributor for the track, add vacuum advance for the street. End of story (unless you need more details?).


[This message has been edited by stingr69 (edited 05-10-2002).]
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post #4 of 5 (permalink) Old May 10th, 02, 04:00 AM
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a vac advance hooked to manifold vac allows for easier cranking at start up at operating temps. and a better running engine at cruise.
If you hook it up to ported vac, Then it becomes a load compensator(I would rather tune the centrifigial weights for that) bottom line if its a streater it should be hooked up.

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post #5 of 5 (permalink) Old May 10th, 02, 08:35 AM
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Matt Jones
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I never follow the 'run ported vacuum on the street' rule, it's really not the best way to go on a high performance motor.

People always try hooking it up, and complain on how it wasn't running as well. Well, if you think about it, you need to limit the amount of advance the vacuum brings in.

My setup is 10 degrees initial, 24 mechanical, and 6 in the vacuum advance (you don't need an adjustable unit to limit it). This way, I get 10 degrees while cranking, 16 degrees at idle. This helps converter hold-back if you have an automatic.

People always say 'you don't know what you're talking about' when I tell them to run manifold vacuum...ask ANY knowledgable ignition specialist. Good ol' Dave Ray comes to mind here....

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