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.
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.