1957 stalls at stop

[jtkse]

My 1957 bird runs great around town. But when on long freeway run when I stop it starts to stumble and if I don’t shift into neutral it will die. I have a good mechanical fuel and I backed it up with an electric. I have a fuel in the fuel bowl when it dies and a New Holley carb. Good tune on engine. Once it dies and sits a minute it starts up and problem goes away until another long run. Checked timing ,Vacuum advance , new points, condenser and coil. I drilled a hole in fuel cap so it is vented. Blew out fuels line and new hoses. New spark plugs and wires. Wrapped fuel lines with heat cover so no vapor lock. Could a transmission torque converter be a problem? It down shifts and up shifts good. Even tried electronic ignition. No help. I keep both fuel pumps working but it runs good without electric one but I tried just in case.

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[sre]

Seems like you covered most of the bases. Do you have a plastic spacer, useally 1" thick between the intake and carb.? might help if not there

 

[74 Harley]

Your idle mixture could be a little bit lean, a lot of carbureted cars had a dash pot for this issue.

 

[jtkse]

Your idle mixture could be a little bit lean, a lot of carbureted cars had a dash pot for this issue.

It will idle for about 10 seconds or so then slowly looses it rpm’s until it dies. Before a long run I can pull up to a stop light and it idles fine

 

[jtkse]

Seems like you covered most of the bases. Do you have a plastic spacer, useally 1" thick between the intake and carb.? might help if not there

Yes I have a spacer. Car is running 180 degrees so not hot. I wrapped the fuel lines from the carb to the frame. Also wrap it in the rear because I thought the exhaust could be a problem

 

[ron56]

If it was my problem I would install a remote fuel pressure gauge. That way you would know where to start looking. Fuel or ignition.

 

[74 Harley]

If you have a Holley 4160 check your float level, then you may want to try a pair of main jet extensions. ( I can't recall their proper name) Anyway they may help. And they're cheap. I used to use them when I built carbs for off road use.

 

[jtkse]

If you have a Holley 4160 check your float level, then you may want to try a pair of main jet extensions. ( I can't recall their proper name) Anyway they may help. And they're cheap. I used to use them when I built carbs for off road use.

I did try swapping a carb with another car that was running good. My carb ran good on their car but theirs did not on my car. Same problem

 

[74 Harley]

I did try swapping a carb with another car that was running good. My carb ran good on their car but theirs did not on my car. Same problem

That's odd. However you may need to check the mechanical advance in your distributor to make sure it is not sticking at full advance.

 

[jtkse]

That's odd. However you may need to check the mechanical advance in your distributor to make sure it is not sticking at full advance.

Put the timing light on it today and both vacuum and mechanical are working properly

 

[74 Harley]

Put the timing light on it today and both vacuum and mechanical are working properly

New thoughts! Do you have power brakes? A vacuum leak in the booster could be an issue.

 

[jtkse]

New thoughts! Do you have power brakes? A vacuum leak in the booster could be an issue.

I will have to block that hose off and drive it. Thanks

 

[Pink T-Bird]

New thoughts! Do you have power brakes? A vacuum leak in the booster could be an issue.

Since the problem remained with the engine and not the carb when you swapped that exonerates the new carb. If there is no black cloud when you restart then it is leaning out to stall rather than getting too rich causing the stall. (Or it could be the ignition, except you've replaced everything.)
Could be a vacuum leak somewhere else besides the brake booster too, like in the booster section of the fuel pump, wiper motor lines, even a intake manifold gasket that opens slightly when hot, like after a freeway run.
On my car the 'T' under the dash that feeds the heater vacuum valve and the wiper motor was leaking a bit. The brittle hose from the T to the wiper motor seemed to the the 1957 original and could no longer seal well. Apparently close enough to the firewall that engine heat exacerbated the leak.

 

[jtkse]

Since the problem remained with the engine and not the carb when you swapped that exonerates the new carb. If there is no black cloud when you restart then it is leaning out to stall rather than getting too rich causing the stall. (Or it could be the ignition, except you've replaced everything.)
Could be a vacuum leak somewhere else besides the brake booster too, like in the booster section of the fuel pump, wiper motor lines, even a intake manifold gasket that opens slightly when hot, like after a freeway run.
On my car the 'T' under the dash that feeds the heater vacuum valve and the wiper motor was leaking a bit. The brittle hose from the T to the wiper motor seemed to the the 1957 original and could no longer seal well. Apparently close enough to the firewall that engine heat exacerbated the leak.

What is strange is when it shuts down it restarts with no problem and runs fine until the next long run

 

[Pink T-Bird]

What is strange is when it shuts down it restarts with no problem and runs fine until the next long run

Well, that's why I'm leaning towards vacuum leak leaning out the mixture to the point of stalling. I presume you pump the gas once or twice before the restart? And you have confirmed there is no black exhaust upon the restart, so it is a lean stall not a rich stall?

My other choices would have been: stuck distributor advance, but you verified that was fine; excess fuel pressure from the combination of both fuel pumps working hard at freeway speed, but that didn't happen with the other carb (and it would be a rich stall); or boiling of the fuel in the bowl because of a missing phenolic spacer under the carb, but you have a phenolic spacer.

Just for fun, have you confirmed the vacuum advance on the distributor is not leaking? I've seen that do weird things. Pull vacuum on it verify it moves, then seal off and hold for a minute or two it should not move back towards the at rest position and the vacum reading should not decay.

You can also check for vacuum leaks by carefully spraying starter fluid at vacuum connections, like at the phenolic spacer, intake manifold gasket, any vacuum connections or transitions from steel to rubber hose, etc. If there is a leak the idle speed will increase from burning the starter fluid. Stay away from ignition wires, coil etc that might spark and light off the fluid outside of the engine.

 

[sre]

I agree with Pink T-Bird on the vacuum advance. I went thru 4 vacuum advance units before I found one that didn't leak. I use the vacuum pump I have for bleeding brakes. I even tried a rebuilt unit that leaked.

 

[jtkse]

Found the problem. Vacuum advance was working good but the e clip that holds the arm was missing. When the arm pulled on the point plate to advance it almost came off the pin and would stick when you released the vacuum. Thank you the help

 

[seatramp]

Well, that's why I'm leaning towards vacuum leak leaning out the mixture to the point of stalling. I presume you pump the gas once or twice before the restart? And you have confirmed there is no black exhaust upon the restart, so it is a lean stall not a rich stall?

My other choices would have been: stuck distributor advance, but you verified that was fine; excess fuel pressure from the combination of both fuel pumps working hard at freeway speed, but that didn't happen with the other carb (and it would be a rich stall); or boiling of the fuel in the bowl because of a missing phenolic spacer under the carb, but you have a phenolic spacer.

Just for fun, have you confirmed the vacuum advance on the distributor is not leaking? I've seen that do weird things. Pull vacuum on it verify it moves, then seal off and hold for a minute or two it should not move back towards the at rest position and the vacum reading should not decay.

You can also check for vacuum leaks by carefully spraying starter fluid at vacuum connections, like at the phenolic spacer, intake manifold gasket, any vacuum connections or transitions from steel to rubber hose, etc. If there is a leak the idle speed will increase from burning the starter fluid. Stay away from ignition wires, coil etc that might spark and light off the fluid outside of the engine.

When chasing vacuum leaks I use a barbecue butane lighter to blow a little butane on the connections with the same idle increase for leaks. Makes it easy to reach the connections, doesn't saturate the area with fumes and flammable liquid, (wiring and hoses don't like it) and you don't risk setting your engine compartment on fire.

 

[Frankie the Fink]

Sounds like fuel percolation to me, next time it happens, pop the hood and listen for the sound of liquid boiling also check the temps, shooting the fuel bowl with an I/R temp gun (Harbor Freight has them for cheap) and if you record anything north of about 140*, then that's the problem. You can also look down the cab bore and if you see fuel driblling from the squirters that's another indication. What happens is that this fuel sits on the intake runners as raw gas and until it dissipates you are starting a "flooded" car.

You can try the following procedure to try an immediate restart. Depress the gas pedal SLOWLY about 1/3 of the way down and crank the car for about 4-5 seconds to clear out the carb throat, then put the gas pedal on the floor and see if the engine starts.

If this is the issue there are several ways to deal with including carb spacers, heat shields, etc..