Vacuum Advance
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Vacuum Advance
Would a 70 390 in an F100 have a timed vacuum advance or a full vacuum advance. I can't seem to get it to run right using the timed port on the carb, but it seems to run ok (no miss) when I use the manifold vacuum port. The distributor is stock for that year and motor. I have replaced everything in the ignition system and plugged the vacuum advance hose in the other port out of desperation. I rebuilt it myself and there are no emissions junk on it.
Sam
Sam
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From: saramento usa
Vacuum Advance
I was told or given advice by a Ford mechanic that the Fords like to run off the manifold vacuum rather than the timed port. I've run mine off the manifold and it runs fine. It will especially idle better in city type driving. You do, however, lose the vacuum advance at WOT since the manifold vacuum drops to near zero in WOT.
Steve
Steve
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Joined: Jun 1999
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From: Greenville USA
Vacuum Advance
The same would apply with timed vacuum, it is just higher on the carb, under full throttle the ported vac advance should not be advancing the timing either, the mechanical advance should be doing the trick.
Vac advance is there to improve idle quality.
Vac advance is there to improve idle quality.
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Joined: May 2004
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From: Regina, Sask. Canada
I have a 1967 F100 with a 1978 351M powertrain. Since I replaced the advance unit (mine too was seized around the distributor main shaft), I've found that it advances too far upon acceleration. I tried two ports on the 2-bbl carb. and both end up with the same results.
Is there another lower-vaccuum place I can try/
Is there another lower-vaccuum place I can try/
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Answering 7 1/2 year old posts will cause you to buy a round of beer for FTE 500 people 
See my emissions album for a vacuum diagram for your engine.
The VA hose runs directly to the heated vauum switch first before it gets to the ported vacuum tube..
See my emissions album for a vacuum diagram for your engine.
The VA hose runs directly to the heated vauum switch first before it gets to the ported vacuum tube..
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Originally Posted by Sam Benham
Would a 70 390 in an F100 have a timed vacuum advance or a full vacuum advance. I can't seem to get it to run right using the timed port on the carb, but it seems to run ok (no miss) when I use the manifold vacuum port. The distributor is stock for that year and motor. I have replaced everything in the ignition system and plugged the vacuum advance hose in the other port out of desperation. I rebuilt it myself and there are no emissions junk on it.
Sam
Sam
http://www.performancedistributors.com/forddui.htm</O
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