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Classic/Antique Car Repair/Model A sputters and coughs when warm


QUESTION: I love your Youtube posts and they have been very useful to me.

I have a 1931 roadster. It is an older restoration but runs well. he has been having a problem for a while now. he as recently been to my mechanic. They are very capable men and have serviced my cars, old and new, for a long time.

Here's the problem. It's maddening because the car now runs like a clock... Redid exhaust leak, new Renner carb, new plugs, points, condenser... Runs and sounds like a masterpiece... However, first part of any trip is lovely. Then after you head home when he is warm, he cuts out and pops through the carb and hesitates and has a fit.

What is the problem?

Any ideas? New coil, sparks like a lightening bolt. Timing is perfect and exact. Fuel flows like a river... It only acts up when it's warm...

It can't be carb or points or condenser or coil they are all new and it was doing this before we replaced everything... have finger filter in gas tank...

Is fuel getting too hot in line? Gas cap? So what do you think? I am flummoxed and frazzled.

I wish I could show you exactly what he does. It only happens when he is warm and is the thing he was doing before going into the doctor. The carb is a rebuilt Zenith done by Renner.


Many thanks,


ANSWER: Ok, try this.  Pull out the gas line from the carb and make sure the ferrule is not set back too far from the end of the tube.  On the zenith, it sometimes hits the round screen in there and blocks most of the flow.  
Get the old condenser and put it on.  You have a higher probability of getting a bad one than you do have it going bad.  
Same with the coil.  The new one may not be good.  Long shot there.

Next time it acts up, throw a bottle of water on the carb bowl.  Your gas may be flashing into a gas.

Try a different carb.  Easy to do.  

Let me know how you make out.  jack

---------- FOLLOW-UP ----------

QUESTION: Apparently. it is the dadgummed evil Ethanol flashing in the bowl...So frustrating, I know that many old-time Model A guys say that is not possible, but it is. We are installing a fiber gasket between the Zenith and the intake manifold to try to stop the heat transference and my guys made a fairly decent looking heat shield to protect the carb. The intake manifold gets blisteringly hot, which I imagine is a whole other problem!Would the intake get this hot due to an exhaust leak or not being tightened enough? The manifold was replaced some time back.

It should not act up once you get it on the road.  Maybe if it's very, very hot, it might, but that cool fuel going in should keep it in liquid form.
Your engine is running way too hot.  Check your timing.  You must be running a little advanced.  I assume your radiator is good and you are not overheating.  I also assume you are not getting combustion gases in your water jacket.  You would be losing coolant if you did.
A lean mixture can increase exhaust temp.  
My guess is that your timing is off, or a bad condenser.  Let me know.  jack

At idle, you should get a nice "Cackle", and with the spark lever all the way down, the engine should lope.  Run with the spark lever all the way down.

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jack bahm


Only repair type questions on the 1928-1931 Ford Model A.


Owned one when I was 15 yrs old, and now have owned 5. Still own and play with 2 of them.

Oakleaf region of MARC. Model A Restorers Club. I have put several Model A videos on the Oakleaf site that may be of help. Things like how to start the A, how to Time it, how to troubleshoot it.. Go to and you will find them. Also, go to and search for "jackbahm" and you will find over a hundred videos. Many about the Model A and our outings. jack

"More than you need to know about cars." Just a small book for Car Nuts. "Model A Ford Tips and Hints" "Get A Horse" (What to do when Henry's Lady quits on you.) or Snyder's Antique Parts. "Engineering Stuff" (For the Kid who likes to take things apart and get them back together). Kids book for ages 10-16. 2012 Many Model A movies that can be found on

BSME LSU, 1958, Masters of automotive engineering from the Chrysler Institute of engineering, 1960, MBA Mich State, 1976. Worked as an engineer at Chrysler from 1958 to the end of 1991.

Awards and Honors
Two patents while working in auto industry. Go to this site for my Model A videos.

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