Carb Probs
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Joined: Aug 1999
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Carb Probs
I have a 2 brl motorcraft carb on a '70ish 429. The problem that I am having is that off idle to when the secondary kicks in. There is just a lot of missing and dosen't like to accelarate until I get on to the secondaries. My brother-in-law says that it is the powervalve that needs to be replaced. Any ideas on what to look for or to do to fix the problem.
Thank You
Thank You
Elder User
Joined: Jun 1999
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From: LAT 46.55501° & LON -122
Carb Probs
I have never heard of a Motorcraft carb like your's before. Most Autolite and Motorcraft 2BBL's that I have seen do not have secondaries, both the left and right throttle plates work together. The only time I have seen that type of carburetor you describe was on 4&6 cyl engines. What kind of manifold and/or adapter are you using with this carb?
If your secondary throtle plate is opening but not recieving fuel then it would cause an overly lean mixture which would give you the problems you describe. If your secondary has a seperate float bowl, then check to see if the float needle is stuck closed.
As your friend said, it could also be a broken power valve. It is basically a diaphram that enrichens the fuel when vacuum drops to a certain level. A new one should come in the carburetor kit you should get for it if you decide to tear it apart.
If your secondary throtle plate is opening but not recieving fuel then it would cause an overly lean mixture which would give you the problems you describe. If your secondary has a seperate float bowl, then check to see if the float needle is stuck closed.
As your friend said, it could also be a broken power valve. It is basically a diaphram that enrichens the fuel when vacuum drops to a certain level. A new one should come in the carburetor kit you should get for it if you decide to tear it apart.
Elder User
Joined: Jun 1999
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From: LAT 46.55501° & LON -122
Carb Probs
Disreguard my second paragraph; I thought you were having problems after your secondary kick-in.
Since your problems are before the secondary, then that might be your accelerator pump, especially if it stumbles right after you push on the gas. If it does not run right in the primary circut even with a light & steady throttle position, then you may have a blockage somewhere in the main jets or booster venturi, or your float level may be off. If only heavy acceleration before the secondaries is affected, and light acceleration is unaffected, then it is probably the power valve.
Since your problems are before the secondary, then that might be your accelerator pump, especially if it stumbles right after you push on the gas. If it does not run right in the primary circut even with a light & steady throttle position, then you may have a blockage somewhere in the main jets or booster venturi, or your float level may be off. If only heavy acceleration before the secondaries is affected, and light acceleration is unaffected, then it is probably the power valve.
Senior User
Joined: Jun 1999
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From: Greenville USA
Carb Probs
I'm pretty sure, too, you don't have secondaries, they are usually only on 4-bbl carbs. A progressive 2-bbl would have to be huge to feed a 429.
Anyway is it a 2100 or 2150 model carb? This it's not progressive. 4300 or 4350 - then its a 4-bbl.
Sounds like your accel (or even perhaps your main jets, they are easily removed once the top of the carb is off.) jets aren't functioning due to clogging, no matter what size it is. Fortunately the 2100 series is one of the easiest to rebuild, just take it apart, clean out the junk in there in a can of carb cleaner, blow it out with compressed air,and reassemble. Rebuild kits are only like $20.
fordmando
78 F-150 4x4 400 4 on floor
86 Nissan 300ZX
George
Anyway is it a 2100 or 2150 model carb? This it's not progressive. 4300 or 4350 - then its a 4-bbl.
Sounds like your accel (or even perhaps your main jets, they are easily removed once the top of the carb is off.) jets aren't functioning due to clogging, no matter what size it is. Fortunately the 2100 series is one of the easiest to rebuild, just take it apart, clean out the junk in there in a can of carb cleaner, blow it out with compressed air,and reassemble. Rebuild kits are only like $20.
fordmando
78 F-150 4x4 400 4 on floor
86 Nissan 300ZX
George
