Vacuum tuning
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Vacuum tuning
I've heard that you are supposed to tune the carb rich for highest vacuum, however I had trouble tuning when I tuned it leaner I got higher vacuum. That didn't seem right and I just don't want to tune it too lean. Anyone know what I'm doing wrong? Thanks.
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From: **** hole San Jose ca.
Having no idea what your working on, but all your tuning should be from manifold vacuum not carb timed port for dizzy. The carb adjustments are for fine tuning should not be overly lean or rich just highest vacuum
Orich
Orich
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Sorry I'm tuning a 360 fe in a 72 f100. I am going from manifold vacuum, but from directions I have read, people are saying to lean it out until it almost dies, which mine wont... but then to turn it rich for highest vacuum then lean a quater turn about then repeat with other screw. Well my problem is that my vacuum goes down when I tune it more rich. And tuning for highest vacuum makes it quite lean so I'm not sure why it's doing this..
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From: **** hole San Jose ca.
If engine won't die when carb air/fuel jets are screwed all the way in the power valve is bad.
If that what your saying. Plus have you checked that the vacuum advance can is good and not sucking air.
Orich
If that what your saying. Plus have you checked that the vacuum advance can is good and not sucking air.
Orich
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From: **** hole San Jose ca.
The redneck way is by sucking on the rubber hose pulled off at the carb. It should hold a vacuum once you suck all the air out. But if you just keep sucking air then it's bad.
Or buy a hand held vac pump tester..
Orich
Or buy a hand held vac pump tester..
Orich
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Okay thanks. I've been looking at symptoms of a bad power valve and I think that might be the problem.
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Did the power valve. Still get pops through the carb... the old one looked worn but I didn't see any holes. I'm thinking jets. I looked and I have size 54 jets and I think I'm going to try down sizing my jets but I don't know how far down to go. I think I was told once 51 to 54? Buy idk how far down to try.
Lead Driver
Joined: Aug 2003
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From: **** hole San Jose ca.
Did the power valve. Still get pops through the carb... the old one looked worn but I didn't see any holes. I'm thinking jets. I looked and I have size 54 jets and I think I'm going to try down sizing my jets but I don't know how far down to go. I think I was told once 51 to 54? Buy idk how far down to try.
Re-Jetting an engine leaner the higher the elevations you get, iirrc it's two sizes smaller per every 2000 ft elv.
Old skool jump 3 sizes if then lean come back one or the other way that would be one larger.. Then go one size at a time as you should be close or right on.
orich
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.....another reason I'm glad I'm (eventually) swapping to Ford EFI. It automatically tunes itself for all weather changes, relative humidity, air density and changes in altitude. No jets to change, no fuel bowls/air horns to remove, no floats to adjust, no spilled fuel on the intake/engine ...or on you and no tools involved for these adjustments to take place. ....in the meantime though, I still have to deal with a carburetor.
Some of the science behind carburetor settings.
Density Altitude Tuning - How To Tune For Changing Weather Conditions - Hot Rod Magazine
Some of the science behind carburetor settings.
Density Altitude Tuning - How To Tune For Changing Weather Conditions - Hot Rod Magazine
Lead Driver
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From: **** hole San Jose ca.
If their was a EFI setup for a FE that had a dizzy that adjusted the timing as needed. Plus a knock sensor, I'd buy it.
But to is day no one has put together one on the market.
Was told they could use the small late dizzy from the efi 5.0 with a FE housing. They know what to use but not enough market yet for it...May be never tho.
Orich
But to is day no one has put together one on the market.
Was told they could use the small late dizzy from the efi 5.0 with a FE housing. They know what to use but not enough market yet for it...May be never tho.
Orich
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From: Antelope Valley ,CA
sorry i goofed , that should have read idle screw not fast idle ( i was up at 4am yesterday for work)
anyways check your throttle plates (look down carb ) they should be closed . If they are open even a little then your idle screw is turned to far in and holding them open . crank the idle screw out till they close and reset your idle mixture screws to like 2 turns out this will give you a good starting point , i like to use 2 Vacuum gauges 1 on manifold 1 on timed , so you can get max vacuum on the manifold with 0 on the timed gauge (or close to it)
anyways check your throttle plates (look down carb ) they should be closed . If they are open even a little then your idle screw is turned to far in and holding them open . crank the idle screw out till they close and reset your idle mixture screws to like 2 turns out this will give you a good starting point , i like to use 2 Vacuum gauges 1 on manifold 1 on timed , so you can get max vacuum on the manifold with 0 on the timed gauge (or close to it)