Running, idling, not driving

[Flathead Fever]

I was a mechanic for 30-years. Sometimes it's hard to tell if it's a fuel problem or ignition problem, especially without a scope to look at the firing pattern. One thing you can try is to take a can of carb spray and spray it into the engine while you open the throttle and if it runs on the spray then it is a fuel delivery problem, if it doesn't and still cuts out it's probably an ignition problem. A lot of timed the jets in the carb will be able flow enough fuel to idle but not enough to drive the car. Like others have said, also check the accelerator pump to make sure it squirts. Even if it was a bad accelerator pump the engine would hesitate when you first opened the throttle but then when the main jets took over it would straighten out. If your engine is falling on its face and staying there after you open the throttle then it's probably not the accelerator pump. Even if the carb was recently rebuilt there is so much junk in these old gas tanks that sometimes the carbs plug right back up again. Make sure there is a large metal, not plastic fuel filter located down on the frame to catch any crud in the tank. You can also easily remove the top from the carb with it still on the engine and look in there to see if there is rust and junk in the float bowl. You can also check the float height while you have the top off. There can be so many different things on an engine to make it run bad, but you have to start somewhere until you finally find the problem.

[35fordtn]

Sure sounds like a condensor

[Seth Swoboda]

Originally Posted by 35fordtn

Sure sounds like a condensor

Agree

[glennpm]

Originally Posted by Flathead Fever

I was a mechanic for 30-years. Sometimes it's hard to tell if it's a fuel problem or ignition problem, especially without a scope to look at the firing pattern. One thing you can try is to take a can of carb spray and spray it into the engine while you open the throttle and if it runs on the spray then it is a fuel delivery problem, if it doesn't and still cuts out it's probably an ignition problem. A lot of timed the jets in the carb will be able flow enough fuel to idle but not enough to drive the car. Like others have said, also check the accelerator pump to make sure it squirts. Even if it was a bad accelerator pump the engine would hesitate when you first opened the throttle but then when the main jets took over it would straighten out. If your engine is falling on its face and staying there after you open the throttle then it's probably not the accelerator pump. Even if the carb was recently rebuilt there is so much junk in these old gas tanks that sometimes the carbs plug right back up again. Make sure there is a large metal, not plastic fuel filter located down on the frame to catch any crud in the tank. You can also easily remove the top from the carb with it still on the engine and look in there to see if there is rust and junk in the float bowl. You can also check the float height while you have the top off. There can be so many different things on an engine to make it run bad, but you have to start somewhere until you finally find the problem.

Good advice here. You mention that "If I hold it at that rev range for about 30s, the engine begins sputtering. Lightly at first, then hiccupping and sputtering. If I let off on the gas hard, there's a 1 in 2 chance the engine just dies. If I let off it gentle, the engine might die." Seems like you are running out of gas due to carb floats being too low and/or junk in fuel supply.