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My '29 has been giving me fits the last couple of weeks. All of a sudden started running rough and stalling at idle, but only after the engine was hot -180 degrees or so.

So, changed condensor, almost killed myself changing the coil under the dash, changed the plugs, filed and gapped the points, car runs fantastic now, better than ever, until it gets warm - about 180. Not spitting and running rough like it was, seems to be just plain old vapor locking. I got the car last August, drove it a fair amount then when it was quite hot down here and never had an issue with this. Now it wants to stall once she's good and warmed up. Experimented, leaving the hood open on carb side, she runs fine, doesn't try to stall.

It's running an electric fuel pump, gravity pump is dead and gutted, but again, it ran fine until the 22nd with this exact same setup. Also changed the fuel filter. Have read the winter blend gas may be part of this issue, running non-ethanol 87 octane fuel. 1-1/2 psi at the regulator, tried upping it all the way to 3, made no difference.

So, anybody got ideas? I've read about people adding all sorts of things to their gas. Finally, this is Louisiana, it was 88 degrees here today with 65% humidity when she started having problems after about fifteen minutes of driving. Thanks!!

No answer for the vapour lock.

But, suggest you delete the duplicate posts on this subject. There is a "delete" button at the bottom of each post which remains "live" only for a few days just for these occurrences.

I have used a product called heat shield on my 28. It works by reflecting the heat away from the the gas line. It has a Velcro like strip on the entire length so I can take if off for shows.

You could also look at shielding your pump but what surprises me is that increasing the pressure did not at least 'help' fix the problem. Did you measure the PSI at the pump output by the carb?

I also tried closes pins (spring loaded kind) but with no success.

Gar

I cant remember who told me here, I think it was JW who told me to run 5% diesel mixed in the gas to help with vapor lock.

Kerosene added to the fuel works better than diesel. Add as much as you can get with a minimum of 10%. Also avoid fuel with ethanol.
I have had two 1929 Packards and both suffered vapor lock in hot weather especially stop-start driving and hill climbing.
When all else fails, carry a bottle of water to wet and cool the carburetor, this gives almost instantaneous relief but only for a very short time.
A fuel circulation system with a return line to the tank can work but the return line flow has to be regulated to prevent starving the carburetor under high fuel demand.
There is no easy fix.

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-> BDC, yes.

-> Yes.

-> Yes.

-> Yes.

I had good luck with 89 octane gasoline. May be better for vapor lock. Try it.

The way I would start to diagnose a vapor lock issue is to determine where and how much the gasoline is being exposed to heat. Take a IR surface thermometer and, and create a chart of surface temps of the fuel pump, the fuel line from the pump to the carburetor, the fuel bowl of the carb, the venturi of the carb, and then various places on the intake manifold. I would take the temps, and write them down every two minutes or so until you achieve your suspected vapor lock conditions. Isolate where the problem is.

Just some immediate thoughts: 1. Try non-ethanol gasoline to see if that helps. 2. Check your fuel mixture, perhaps its too lean. 3. Wrap the exhaust downpipe with a wrap to shield the pump/carb from heat absorption. Also 180 sounds hot to me; my 31 Standard only gets to 150 at the upper radiator neck. Perhaps you have a cooling issue like a clogged radiator, poor water pump or rusted out water jacket and block scale that is resulting in too much engine heat for things to run optimally?

I agree with Greenfield, your running temperature of 180 degrees F. indicates to me the likelihood of a preexisting overheating condition. I would expect a properly performing cooling system to be more like 160 degrees.

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Rebuilt engine with about 800 miles on it. Radiator flushed out and clean, running 50/50 and distilled water. I'm in Louisiana it's 85 to 95 degrees down here. Nothing runs at 150 degrees, ever, here. On the occasional days when we've gotten into the 40s, she runs between 140 and 160 but those days are few and far between. She's actually running a little rich, always prefer them a bit rich rather than too lean. I'm 90% sure the vapor lock is occurring in the intake above the carb as the 87 octane gas vaporizes before entering the cylinders. Reason being, she won't lock with the hood open. Close the hood, seal the heat in, she starts starving and will stall in just a few minutes after she's warmed up.