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07-15-2020, 05:18 PM | #1 |
Member
Join Date: Aug 2013
Location: Long Island NY
Posts: 72
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Model A Bucking at 45 mph plus
Model A Bucking at 45 mph plus
The car is a A with indented firewall with a B engine, A head, converted to 12V, running a B carb and B distributor, 3.0-ohm coil, new condenser, cleaned points and replaced inline gas filter. The car idles well and runs well up to 42-44 mph. As speed is gradually increased to 50-55 mph the engine starts bucking and will to continue to buck until the speed is decreased to 42-45 mph again and then run well. The car has been driven 25 + miles at one time during the same day with the same response each time. A response to a solution from the members of the Ford barn membership is appreciated. Sofield |
07-15-2020, 06:02 PM | #2 |
Senior Member
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Re: Model A Bucking at 45 mph plus
Not getting enough fuel into the carb bowl. I don’t know about B carbs, but if it’s like the zenith, your fuel line might be pressing against the screen in the carb.
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07-15-2020, 06:27 PM | #3 |
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Join Date: Mar 2017
Location: Connecticut Shoreline
Posts: 1,819
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Re: Model A Bucking at 45 mph plus
Fuel problem.
I might start by takings apart and cleaning the carburetor. Check fuel lines and also the gas cap. Is there a air cleaner? If so, is it clean? I think its something on the fuel/air side of you engine. Enjoy. |
07-15-2020, 06:43 PM | #4 |
Senior Member
Join Date: May 2010
Location: Largo Florida
Posts: 7,225
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Re: Model A Bucking at 45 mph plus
Yep, sounds like fuel starvation. Try loosening the fuel cap, may be a vent issue. At least its an easy first thing to try.
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07-15-2020, 07:19 PM | #5 |
Senior Member
Join Date: Jan 2019
Location: Florida Panhandle
Posts: 585
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Re: Model A Bucking at 45 mph plus
Does the shutoff valve on an indented firewall have a pencil filter like the earlier models ? If so, worth checking. Does sound like fuel starvation.
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07-15-2020, 10:13 PM | #6 |
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Join Date: Apr 2012
Posts: 63
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Re: Model A Bucking at 45 mph plus
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07-16-2020, 05:47 AM | #7 |
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Join Date: Sep 2019
Location: Germany
Posts: 215
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Re: Model A Bucking at 45 mph plus
If it's a fuel problem I guess it should happen in 1st and 2nd gear as well if you reach high rpms, you could check that.
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07-16-2020, 09:54 AM | #8 |
Senior Member
Join Date: May 2016
Location: Scottsdale, Arizona
Posts: 611
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Re: Model A Bucking at 45 mph plus
Good Morning...Just a thought, but check your point gap...Your rubbing block might have worn down a bit and your points are closer than 0.018. Could also be a sign of a coil that is a bit long in the tooth...same with your condenser. Ernie in Arizona
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07-16-2020, 09:55 AM | #9 |
Senior Member
Join Date: May 2010
Location: Alabama
Posts: 8,099
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Re: Model A Bucking at 45 mph plus
I would check float height in the carburetor , Five eights is the correct float setting . If the float setting is too low , the engine will starve for gas at higher speed .
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07-16-2020, 11:58 AM | #10 |
Senior Member
Join Date: May 2010
Location: Plano, Texas
Posts: 840
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Re: Model A Bucking at 45 mph plus
Agree float height.
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