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Old 03-26-2021, 05:33 PM   #1
Neshkoro
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Default Engine stumbles on acceleration

Hi folks,
I need some help.
I bought this 1930 Model A Ford Tudor last September. I've been going through some things that need attention. I just finished rebuilding the steering box, did a tune up. New plugs, cap, rotor, ignition coil and condenser. The points looked good. I just finished rebuilding the Tillitson Carb. The car starts and idles good. While driving, if I accelerate, it begins to stumble and bog down. I've checked the timing and the points gap and they seem to be correct. Fuel flow to the carb is good. I checked the compression. They range between 50 and 60 PSI. I've installed a fuel filter between the gas tank and the carb.
THOUGHTS?

Thanks,
Bill
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Old 03-26-2021, 06:03 PM   #2
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Default Re: Engine stumbles on acceleration

Take the filter off and try it.
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Old 03-26-2021, 06:16 PM   #3
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Default Re: Engine stumbles on acceleration

I agree with JacksonIII. FIlters are unnecessary unless you’ve got rust dust in your gas tank, and that is best resolved with a pencil filter at the shutoff. Otherwise your sediment bowl should be adequate. If you have the steel bulb type sediment bowl, open it up and make sure it isn’t clogged.
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Last edited by 700rpm; 03-26-2021 at 08:12 PM.
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Old 03-26-2021, 06:31 PM   #4
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Default Re: Engine stumbles on acceleration

Is your gav set properly? Might be running it lean
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Old 03-26-2021, 06:59 PM   #5
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Old 03-26-2021, 07:32 PM   #6
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Default Re: Engine stumbles on acceleration

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Marshall,
Thanks for the PM. I'll remove the fuel filter and do as you suggested. I wont be able to get back to the for a couple of weeks. As soon as I do, I'll reply with the results. Thanks so much.
Bill
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Old 03-26-2021, 08:38 PM   #7
Marshall V. Daut
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Default Re: Engine stumbles on acceleration

Only any fuel filter between the sediment bowl and carb, not the pencil filter inside the gas tank or the round filter screen inside the sediment bowl. See that the sediment bowl screen is clean. Also remove any external air filter on the back of the carb to test if that's affecting the acceleration by choking fresh air intake.
M.
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Old 03-26-2021, 08:48 PM   #8
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Default Re: Engine stumbles on acceleration

I had something similar happen with mine. Turned out the aftermarket shaft between the distributor and oil pump wasn't locking in properly. Idled great but ran like crap when you revved it.
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Old 03-26-2021, 08:57 PM   #9
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Default Re: Engine stumbles on acceleration

On a side note, you said the points looked good and you adjusted them. I would recommend as a matter of habit, when doing a tuneup, always replace the points. They are inexpensive and without dressing them you will not get a proper gap setting due to the burning away of material.
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Old 03-26-2021, 09:32 PM   #10
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Default Re: Engine stumbles on acceleration

Quote:
Originally Posted by Marshall V. Daut View Post
Only any fuel filter between the sediment bowl and carb, not the pencil filter inside the gas tank or the round filter screen inside the sediment bowl. See that the sediment bowl screen is clean. Also remove any external air filter on the back of the carb to test if that's affecting the acceleration by choking fresh air intake.
M.
I have high respect for Mr. Daut, but my experience re: pencil filters vs inline filters is just opposite of his. I ageee on the sediment bowl advice.
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Old 03-26-2021, 09:46 PM   #11
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Default Re: Engine stumbles on acceleration

Quote:
Originally Posted by Neshkoro View Post
Hi folks,
I need some help.
Thanks,
Bill
Hi Bill -
Please edit your profile and add your location. You may have other members close by that could help you out.
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Old 03-26-2021, 11:08 PM   #12
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Default Re: Engine stumbles on acceleration

Just a thought...try loosening or removing the GAS CAP? Also you could check the gas FLOW at the carburetor. Try changing to a known working carburetor.

Last edited by ArtimusGordon; 03-26-2021 at 11:13 PM.
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Old 03-27-2021, 07:09 AM   #13
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Default Re: Engine stumbles on acceleration

It sounds as though you may be running a bit lean. Open the gas cap and open the GAV [ choke rod] to 1- 1.5 turns and also the idle mix screw.

I'm one of the few that uses an in-line fuel filter with no issues.
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Old 03-27-2021, 07:16 PM   #14
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Default Re: Engine stumbles on acceleration

When I bought my P/U 30 years ago it had an in-line fuel filter and continues to have one today. Never had a filter problem.
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Old 03-28-2021, 06:06 PM   #15
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Default Re: Engine stumbles on acceleration

Patrick L,
You mentioned the idle mix screw. Turning the screw in or out makes no difference at all on how the car idles. Although, once it warms up, it does seem to idle OK. I placed an order for a bunch of ignition parts. As soon as I can, I will try the things that you folks suggested and report back.
thanks again.
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Old 03-28-2021, 07:13 PM   #16
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Default Re: Engine stumbles on acceleration

You might have the idle speed a bit too high if the idle screw does nothing. Or the idle passages didn't get cleaned enough. The idle mix screw adjusts air not fuel.
These carburetors are pretty simple and it usually takes a lot of cleaner and compressed air to get them clean. A tag wire worked thru the passages is usually needed, then flushed and blown clean.
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Old 03-28-2021, 07:49 PM   #17
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Default Re: Engine stumbles on acceleration

It may be a long shot, but last year my car started running rough when accelerating and also had higher than normal fuel consumption. The cause was the compensator jet in the carb had come loose resulting in a rich mixture. A quick snug-up with a screwdriver and all was well.
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Old 03-29-2021, 09:16 AM   #18
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Default Re: Engine stumbles on acceleration

I’m going to check the idle speed once it warms up and will set it as low as I can get it to idle. Then I’ll try to adjust the idle screw. The bottom half of the Tillitson carb is warped. It will seal on the air inlet portion or the fuel bowl portion. I chose to get it to seal better on the air inlet portion. The top portion is easy to flatten out with a piece of sandpaper and a flat plate. The bottom half, not so easy!
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Old 03-29-2021, 10:03 AM   #19
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Default Re: Engine stumbles on acceleration

The Tilly's are prone to warpage.
I've been able to straighten them out by sanding and filing.
Some folks have a way to do it in an oven/stove.
When you try to remove the main jet you have to be careful not to ruin the threads.
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Old 03-29-2021, 10:24 AM   #20
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Default Re: Engine stumbles on acceleration

Oh, I missed that detail about the Tilly carb. My suggestion doesn't apply, I think.
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