Flathead loses power under load

M

mitch3951

Junior Member
Hello,

I have a 1939 ford that I've been having problems with, I rebuild the original carburetor (A Ford 94) It will idle fine and even run fine but in 3rd gear at about 60 mph it will bog down, spit and sputter but I'll let up on it and it will go away its not a constant thing it will do it then it won't. Is this still a carburetor issue or is it electrical like in the distributor? it has the original helmet style distributor as well. I'm at a loss on what it can be. I'm new to Flatheads and I'm only 22 years old so its learning experience. Any help would be appreciated. Thank you!!
 
Mitch, welcome to Ford Flatheads! Sounds like you enjoy greasy fingernails, they are part of the hobby! It does sound like a fuel delivery issue rather than electrical. I'd start by checking the flow from your fuel pump. Disconnect the line to the carb, and with ignition off, crank it steadily while directing the fuel line into a container. You should get a strong, pulsating stream. If not, your pump may be at fault (weak spring, worn fulcrum, bad valves, leaking gasket), your flex line may be collapsed inside, your line from the tank is restricted, or sucking air at any place in the system. I assume you've rebuilt your carb to the book, but it wouldn't hurt to recheck float level, float valve (metal not rubber), junk in the bowl restricting the main jets, junk in the internal passages, and correct operation of the power valve. About the power valve, check its function by sucking on it. Suction holds to your tongue one way, not the other. Then check its gasket surface to be flat, with no radius at the threads. The power valve (economizer) gasket must not leak. Please report your findings, and let's see some pics!
 
I'll check the fuel pump today. But everything is new. New tank. Fuel lines. Rubber line. Fuel pump from Bob drake. So that's what is leaving me question the issue because everything is new within the last 6 months. Not sure why but it won't let me upload photos. Will keep trying. Thanks.
 
I had symptoms in my 34 which were similar to yours. The problem went away when I completely removed the old ethanol gasoline from the system and put in fresh non ethanol gasoline. I also used some HEET to remove any possible moisture from the fuel delivery system.
 
Mitch, In this day and age, the term "new" has a different definition that it had in the past. Every "new" part these days is highly suspect as to pertains to quality and specifications, even from well known and respected manufacturers and suppliers. Also, you should delete the word "rubber" from your vocabulary for anything that comes in contact with modern fuel. Bob Shewman makes an Ethanol compatible flex line. He advertises in the V8 Times, the publication from the EFV8CA.
 
I had a very similar problem with my 41 truck. I thought it was the fuel pump, but I took my carburetor off and cleaned it again, making sure all the little passages were clear. I put a fuel filter on the fuel line just before the fuel pump and that problem was solved. I had rebuilt the carb a month or so earlier but I think something got in it. I think it is very important to have a good fuel filter. I got a generic one from autozone.
 
Thanks for all the help guys. I think I figured it out. Ended up changing the coil and condenser. After going through the whole fuel system a couple more times. So far no issues. But time will tell. I know MGG mentioned going to unethanol gas is that a good idea to do?
 
Ethanol gas has no redeeming qualities for use in a flathead that I'm aware of. Ethanol eats up about anything that is not stainless steel. It will eat up fuel tanks, fuel lines and aluminum in carburetors/fuel pumps. It destroys noncompatable rubber products. It also contributes to vapor lock.
 
Ethanol also draws moisture which you do not want in your fuel system. After replacing and/or rebuilding 5 of my small engine carburetors, (Mowers, etc.), I switched to non ethanol for all of my small engines about 7 years ago and have had no problems with them whatsoever, even after sitting idle through the long northwest winters.
 
MGG said:
Ethanol also draws moisture which you do not want in your fuel system. After replacing and/or rebuilding 5 of my small engine carburetors, (Mowers, etc.), I switched to non ethanol for all of my small engines about 7 years ago and have had no problems with them whatsoever, even after sitting idle through the long northwest winters.
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Same here!
 
We're really lucky up here in Minnesota. Thanks to the efforts of the MSRA at the legislature and the marine industry, almost every station up here has "non-oxygenated" (no alcohol) gas.

I've never had a fuel related problem, but I'm not taking any chances.
 
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