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  Vacum Advance Adjustment???

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Author Topic:   Vacum Advance Adjustment???

Posts: 16
From: CO
Registered: Jul 2000

posted 06-05-2002 08:00 AM     Click Here to See the Profile for CannedHeat   Click Here to Email CannedHeat     Edit/Delete Message   Reply w/Quote
I have a Mallory Unilite distributor with vacum advance installed in my modified 289. When I rev it to 2000 rpm and hold it there, it has a slight miss. When I take the vacum advance line off the dist. and plug it and do the same, the engine revs very smooth with no misses. The vacum advance looks as if its adjustable but I am unsure of if this will cure the problem or which way to adjust it. Also, even though my motor is modified, do I still check for 36 degree's total advance? I am also using the ported vacum on the carb. Any help on this guys??

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Posts: 366
From: France
Registered: Apr 2002

posted 06-05-2002 11:04 AM     Click Here to See the Profile for Pierre   Click Here to Email Pierre     Edit/Delete Message   Reply w/Quote
I am by no mean a pro, but here is my experience
Your vaccum should be connected to the port on the carb that shows no vaccum at idle (above the throttles) and increasing vaccum as throttle plates open.
Adjust your initial advance to the maximum value (vaccum disconnected)before your engine starts pinging.
Then you have to play with your various adjustment (vaccum advance, mechanical advance) to find the right curve. Keep in mind that you should have a maximum of 36-40? of advance(depends on what octane you are running)by 3000 RPM.

I ended up disconnecting my vaccum and not using it (gave me the most torq at low RPM !). I set my initial at 16? and my mechanical at 24?.

Any Professional opinion on that ?

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Posts: 975
From: Charlotte NC usa
Registered: Apr 2001

posted 06-05-2002 12:51 PM     Click Here to See the Profile for Mpcoluv   Click Here to Email Mpcoluv     Edit/Delete Message   Reply w/Quote
For stock cars, Pierre is correct, run ported vacuum.
For cars with a healthy cam run full manifold vacuum to the distributor.

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