Vacuum Advance
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Laughing Gas
Joined: Nov 2001
Posts: 968
Likes: 71
From: Cherryville,N.C.
Vacuum Advance
I am having problems with hesitation on my truck.I changed the accelerator pump diaphram and did not help.I took the vacuum line off the advance and nothing changed.Is this normal or do I have problems with the advance?I have a rebuilt distributor from NAPA.I have no timing light but I have advanced the timing up but did not seem to help.1973 F-100 with 360 engine and motocraft carb.Russell
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Laughing Gas
Joined: Nov 2001
Posts: 968
Likes: 71
From: Cherryville,N.C.
The distributor came with the vacuum advance installed.The vacuum line is hooked up to the the base of the carburetor.How can I find out what the settings should be on the pump.As far as I know the rod has been at the same place since the truck was new.It is in the top hole on the brackett now.Truck has original carb and engine with 180,000 miles on it.Thanks,Russell
New User
Joined: Jan 2008
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Start it up and spray some carb cleaner with wand attached right at the throttle rod bushing to see if it is leaking.
This is popular spot for carbs to wear out first and there is apparemtly no fix for it. The carb has to be replaced
This is popular spot for carbs to wear out first and there is apparemtly no fix for it. The carb has to be replaced
Lead Driver
Joined: Nov 2000
Posts: 6,628
Likes: 345
From: Albuquerque
You can check the vacuum advance by pulling the hose off the carb or manifold. Suck on the hose and you should hear the engine speed increase a little. Or look inside the dizzy to make sure the mechanism moves when you do this. Your vacuum line may also run through a temp. switch which could go bad.
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Laughing Gas
Joined: Nov 2001
Posts: 968
Likes: 71
From: Cherryville,N.C.
Well I sprayed carb cleaner around the throttle linkage and body with truck running and nothing changed.I do not have any pinging at all.I took the cap off and sucked on the vacuum line and the advance moved, but it sure is very strong.I thought about changing the power valve but the carb has to be removed for this I think.The truck just seems sluggish at normal driving,but with the pedal to the metal it winds out fine for a 360.Russell
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Get a timing light, and see if your timing mark is steady. If the mark is jumping around 6 to 10 degrees, you might have a bad module or magnetic pick-up.
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Laughing Gas
Joined: Nov 2001
Posts: 968
Likes: 71
From: Cherryville,N.C.
Thanks guys,but I don't have electronic ignition.I guess I should get the timing checked first before I buy a carb.My choke does not work that good and I figured it would be best just to replace it.Russell
Posting Guru
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Put the accelerator linkage in the hole nearest the pivot point. How did u get the dist in and timed without a lite? Loosen the dist hold down and with the engine idling turn the dist clockwise and see if it speeds up. Usually if it does you are advancing the timing in a working range. Adjust it back and forth between fastest idle and slowest idle putting it on the faster part of idle but not the fastest. Should be in the ballpark so to speak. do you have a vacuum gauge?
New User
Joined: Jan 2008
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ALL Right.. I finally found my 1973 service specs book. (Tidying up helped me find it)
Here are your settings to factory.
Choke - Index
Accelerator Pump index setting
Auto Trans - 2A Inboard
Manual Trans - 3A Inboard
Here are your settings to factory.
Choke - Index
Accelerator Pump index setting
Auto Trans - 2A Inboard
Manual Trans - 3A Inboard
Junior User
Joined: Dec 2005
Posts: 82
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From: Estes Park
I had a motorcraft 2 brl on a 79 F-150 I could never get just right, I rebuilt it and fiddeled with it for a long damn time, finally I just stuck anouther one on and the truck ran great. I would check the timing first to make sure its right on, after that if it still runs like crap quit messing with it and stick a new carb on it, it saved me a big pain in the ***. Jesse
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Originally Posted by leonharu
Yes,I have a vacuum gage.Where should I hook it up and what should a good reading be? Russell
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