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Old 08-23-2019, 11:11 AM   #1
Sparta
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Default My model A wont go faster than 40-45

Hey guys! Iíve got a bone stock 1931 ford model A. It has a rebuilt engine with steel valves and bearings instead of Babbits. I just out on a rebuilt carb trying to solve the issue, which solved my backfiring issue, but car is still sluggish. The previous owner mentioned that the timing was off and that he fixed it before selling me it. The idle isnít very steady, meaning it has intermittent hesitations when idling. Other than that, what else could it be? Could timing being alittle off cause the car to top out at 40?

Thanks
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Old 08-23-2019, 11:18 AM   #2
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Default Re: My model A wont go faster than 40-45

Have you tried re-timing it??
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Old 08-23-2019, 11:19 AM   #3
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Default Re: My model A wont go faster than 40-45

Does it have a 4:11 rear end? Does the throttle open fully for sure?
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Old 08-23-2019, 11:22 AM   #4
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Default Re: My model A wont go faster than 40-45

I dont know what gear ratio it has...and I’m not sure if throttle is fully open. I can check if the linkage is allowing it to open entirely.

No, I haven’t tried retiming it. Perhaps it’s worth a shot?
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Old 08-23-2019, 11:46 AM   #5
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Default Re: My model A wont go faster than 40-45

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Originally Posted by Sparta View Post
Hey guys! I’ve got a bone stock 1931 ford model A. It has a rebuilt engine with steel valves and bearings instead of Babbits. I just out on a rebuilt carb trying to solve the issue, which solved my backfiring issue, but car is still sluggish. The previous owner mentioned that the timing was off and that he fixed it before selling me it. The idle isn’t very steady, meaning it has intermittent hesitations when idling. Other than that, what else could it be? Could timing being alittle off cause the car to top out at 40?

Thanks
Yes on timing as likely the problem.

Timing the Model A is a little bit of and "acquired skill." Primary to remember is keeping the engine motion "forward" always to take up any lost motion in the moving parts.

From your descriptor, I take it you haven't had the pleasure yet? You really should. Follow the directions which appear in several placed on the Internet, and in several books.

After you get the engine to what you think is "the magic spot," (top dead center) and have moved and fastened your cam, a check you can make is to use the spark advance lever. With the ignition ON move the advance lever to the fully advanced condition (lever all the way to to the bottom.) THEN without having moved anything in the engine, move the spark advance lever up to the fully retarded position. As you near the top of travel in a quiet garage you should hear the points open and the sound of the spark. The closer you can get this to happen at the fully retarded (top) position, the closer you are to correct timing.

Having someone hold a screwdriver on the distributor cam in the direction of rotation (CCW) will help make this check consistent - there is some tendency for the motion of the points traveling around the cam to pull it slightly and introduce lost motion. Not too tight on the screwdriver lest it undo the distributor cam screw.


Anyway, give timing a whirl. It's not that hard.

Joe K

(I have done this check myself by moving the connector lever on the side of the distributor rather than at the steering column. But two people can do it if one is at the driver's seat.)
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Old 08-23-2019, 11:47 AM   #6
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Default Re: My model A wont go faster than 40-45

Start with the basics. Basically a tune up. Usually a good idea to do on a vehicle that is unknown, new to you. The hesitations you mention might be tune up needs.
Pull check/clean/gap plugs.
Check/clean/adjust Points gap.
Check that at full spark advance the distributor upper plate arm is against one side of the Distributor body opening, and at full retard the arm is against the other side of the distributor opening.
With spark set at full retard, check/set timing via the timing pin method.
Remove throttle linkage at the carb, manually exercise the Throttle plate - check it is free and goes completely open and closed. Re-attach linkage and insure it goes completely closed to completely open via the foot pedal.
If the vehicle is a pickup, it is possible it may have a 4.11 rear end, which reduces top speed. Typically cars do not have a 4.11 rear end.


Depending on your experience level, at this point you may want to find someone with experience help you. Start with the basics, so they can be ruled out.
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Old 08-23-2019, 12:10 PM   #7
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Default Re: My model A wont go faster than 40-45

I would probably check for a nice steady, consistent flow of fuel to the carburetor. Try opening up the GAV on the carburetor and see if that picks up speed. May be running to lean on that.
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Old 08-23-2019, 12:20 PM   #8
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Default Re: My model A wont go faster than 40-45

Remove your fuel line from carb, and make sure the ferrule is no more than a 1/16 inch from end of tube. If too long, it will hit filter and block a lot of the fuel flow. Easy to check. Good luck.
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Old 08-23-2019, 03:12 PM   #9
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Default Re: My model A wont go faster than 40-45

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Remove your fuel line from carb, and make sure the ferrule is no more than a 1/16 inch from end of tube. If too long, it will hit filter and block a lot of the fuel flow. Easy to check. Good luck.
If it is a fuel problem it would be bucking and popping I think. Cars that were sold in hill country also had 4:11 gear sets.
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Old 08-23-2019, 04:37 PM   #10
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Default Re: My model A wont go faster than 40-45

deleted info about speed ...

Marshall,

I agree with your recent decision!

Last edited by Benson; 08-24-2019 at 09:50 AM.
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Old 08-23-2019, 06:15 PM   #11
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Default Re: My model A wont go faster than 40-45

A lot of little things can add up to a larger problem. Even if I know who rebuilt an engine, I still wouldn't take condition for granted. I'd make sure it has good compression on all four cylinders. Shake the distributor body and the shaft several ways to see if there is any looseness. Cast iron carb bodies stay pretty straight on the flange over time but the aluminum body Tillotson types can warp & cause a vacuum leak. Any carb can have a loose throttle shaft that will cause a vacuum leak. Loose intake manifold?. All these things can cause up and down rpm fluctuations. Someone already mentioned the GAV rod control or choke/high speed mixture valve control. The mixture can be adjusted at speed but it's a pain to reach over there while driving to do this. Adjusting the timing is not too bad a project once you get the hang of it. The points have to open at the right time or it will be a slug a bug. I just follow the Ford procedure to adjust timing and synchronize the spark control so it can be properly retarded for starting then advanced for running.

Pull the engine through with the hand crank to make sure it has no bearing issues. With no spark plugs installed, it should pull pretty easy. Valves may have been changed to stainless steel from the original steel type stems. I prefer the old steel stems or at least a bronze liner in the guides with stainless type stems. The SS stuff likes to gall if the clearances are too close. You don't need any sticky valves for sure.
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Old 08-23-2019, 08:48 PM   #12
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Default Re: My model A wont go faster than 40-45

Throttle Control Linkage may be bent! check easy things first!
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Old 08-23-2019, 09:24 PM   #13
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Default Re: My model A wont go faster than 40-45

Quote:
Originally Posted by Sparta View Post
Hey guys! Iíve got a bone stock 1931 ford model A. It has a rebuilt engine with steel valves and bearings instead of Babbits. I just out on a rebuilt carb trying to solve the issue, which solved my backfiring issue, but car is still sluggish. The previous owner mentioned that the timing was off and that he fixed it before selling me it. The idle isnít very steady, meaning it has intermittent hesitations when idling. Other than that, what else could it be? Could timing being alittle off cause the car to top out at 40?

Thanks
Just remember Sparta there are more lies told about the size of fish caught, even bigger lies about the ones that got away, more lies told about the yields of crops and lies told about the speed of Model A's. cheers, gary
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Old 08-23-2019, 09:47 PM   #14
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Default Re: My model A wont go faster than 40-45

The intermittent miss at idle can be timing that is more advanced than necessary for idle. It should smooth out if you retard it some. But being sluggish sounds like it is too far retarded. I concur look at your timing rods first for full travel, set the points, then time it. Rember point gap affects timing as well.
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Old 08-23-2019, 11:04 PM   #15
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Default Re: My model A wont go faster than 40-45

Question to you gurus.

This might be the thread to ask a torque question.
My tourer had torque, it could almost be shifted to top at walking pace. I have replaced the spark plugs with new, the smaller diameter thread type with an adapter spacer. It is correctly timed and correctly gapped but lost much of that torque. A shift on the advance/retard lever makes no difference. I notice the gap in the old plugs is much bigger than the new.
Question. Would this gap be the cause of reduced torque.
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Old 08-23-2019, 11:42 PM   #16
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Default Re: My model A wont go faster than 40-45

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Originally Posted by woofa.express View Post
Question to you gurus.

This might be the thread to ask a torque question.
My tourer had torque, it could almost be shifted to top at walking pace. I have replaced the spark plugs with new, the smaller diameter thread type with an adapter spacer. It is correctly timed and correctly gapped but lost much of that torque. A shift on the advance/retard lever makes no difference. I notice the gap in the old plugs is much bigger than the new.
Question. Would this gap be the cause of reduced torque.
Throw the old plugs back in and see if the power comes back.
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Old 08-24-2019, 12:15 AM   #17
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Default Re: My model A wont go faster than 40-45

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Could timing being a little off cause the car to top out at 40?

Thanks

Yes, that; point gap, movement of the lower plate, and use of spark lever all can effect top end.
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Old 08-24-2019, 01:15 AM   #18
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Default Re: My model A wont go faster than 40-45

Check to make sure that your coil polarity is correct.



I had a similar problem and it turned out that the coil polarity was reversed. Once I had switched the wires on the coil, the engine ran like a Swiss watch.

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Old 08-24-2019, 02:55 AM   #19
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Default Re: My model A wont go faster than 40-45

Quote:
Originally Posted by 40 Deluxe View Post
Throw the old plugs back in and see if the power comes back.
Hi Deluxe. Well of course, that would be a simple and effective test wouldn't it. thanks, gary
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Old 08-24-2019, 03:03 AM   #20
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Default Re: My model A wont go faster than 40-45

time to buy a race horse.............
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