Vacum Advance
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Freshman User
Joined: Feb 2000
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Vacum Advance
How hard is it to replace the vacum advance? I have a '70 F-100 with a 302 in it. It will backfire through the carb (not too hard) when I try to accelerate quickly and I was told this was probobly the problem. The carb was recently rebuilt.
Thanks in advance.
Thanks in advance.
Post Fiend
Joined: Feb 2000
Posts: 5,130
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From: Brea CA
Vacum Advance
The vacuum advance is very easy to replace but I don’t believe it’s the cause of your backfiring through the carb. You can run without a vacuum advance and all you would get is even worse mileage. The usual culprits are:
1. Too much initial timing or centrifugal advance spring(s) broken
2. Crossfiring due to bad dist. cap, rotor and/or wires
3. Carb. way too lean while accelerating
4. Vacuum leaks
5. Sticking intake valve(s)
If you know your vacuum advance is bad, go ahead and replace it (keep an eye on that tiny C-clip) but go ahead and check out the other causes.
Your welcome in advance!
1. Too much initial timing or centrifugal advance spring(s) broken
2. Crossfiring due to bad dist. cap, rotor and/or wires
3. Carb. way too lean while accelerating
4. Vacuum leaks
5. Sticking intake valve(s)
If you know your vacuum advance is bad, go ahead and replace it (keep an eye on that tiny C-clip) but go ahead and check out the other causes.
Your welcome in advance!
Senior User
Joined: Mar 2000
Posts: 147
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Vacum Advance
the vacuum advance is easy to replace. there are 2 screws holding it to the base of the dist. and then there is a clip inside the dist. that must be removed. careful it is very small and can be easily dropped you dont even have to remove your points to do it. im not sure if changing this will fix your problem. i have sort of the smae problem. i changed my jet size and it got a lot better. i went from a size 64 to a size 68 on my 352
i run a holley 600. now it only pops when it is cold (i dont run a choke) hope this helps.
mattb
i run a holley 600. now it only pops when it is cold (i dont run a choke) hope this helps.
mattb
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Vacum Advance
Actually, I get around 16-17 mpg on the highway and 13-14 in town. I drive slow though.
Here is some more info on the problem. My truck sat for around ten years. Three or four years ago I replaced the carb. and a couple of other parts and drove the truck around a little. I don't remember it backfiring at all. Last summer I worked on the truck some more and got it back on the road. One of the first things I noticed was the backfire through the carb.
Rebuilding it helped some, and the distributor cap, rotor, and all spark plug and coil wires are new. Something must have happened or went bad during the last three years when the truck sat. The truck is in really good shape though.
Thanks for the help.
Here is some more info on the problem. My truck sat for around ten years. Three or four years ago I replaced the carb. and a couple of other parts and drove the truck around a little. I don't remember it backfiring at all. Last summer I worked on the truck some more and got it back on the road. One of the first things I noticed was the backfire through the carb.
Rebuilding it helped some, and the distributor cap, rotor, and all spark plug and coil wires are new. Something must have happened or went bad during the last three years when the truck sat. The truck is in really good shape though.
Thanks for the help.
