Vintage Cars: 1940 Chrysler Traveler, electric fuel pump, vacuum levels

Question
Hi, when driving the car after it's warmed up it starts to spit and sputter, getting worse and worse until it eventually stalls.  It won't start again until the engine cools down. The carb is rebuilt (and adjusted correctly), new: cap, rotor, condenser, plugs, wires, coil. No one I've talked to can figure it out. The car is 8 cyl, stromberg carb, fluid drive.  I appreciate any advice you have.  Thanks.  Bob

Answer
I am not an expert on this particular topic, but I will run through the possible solutions that I am aware of.

Is this car equipped with an electric fuel pump, or the standard mechanical pump? If it is an electric, make sure that you're not getting more than about 1 1/2 psi fuel pressure at the carburetor. I've had problems with this on my own car, where the electric pump slowly floods out the engine because of too high pressure.

Another possibility is that of vapor lock - is the fuel line from the pump to the carburetor properly routed, and shielded from the exhaust manifold and other heat sources? You could be getting percolation in the fuel line itself - modern fuel is MUCH more volatile than the 50 octane fuel of 1940. I have heavy insulation on my fuel line and a thick heat shield between the exhaust manifold and the fuel line - I was having problems with this as well.

Finally, is the vacuum level correct and steady? If the valves are not correctly adjusted for lash, it is possible that your vacuum levels are fluctuating and affecting the advance on your distributor. I'm not sure if the '40 Chrysler had vacuum advance, but if so, this could be another issue to look at.

I hope this helps you - I'm not a master mechanic by any means, but these are issues that I've run into myself with my own car.

Please let me know what the final solution is - you can never have too many anecdotes about solving problems with these cars!