Vapor Lock - Vintage Cars

I first became aware of the use of an electric fuel pump to overcome vapor lock decades ago when my friend in the ACCCC (Antique & Classic Car Club of Canada) told me that he has an electric pump on a toggle switch for his 32 Plymouth.  Whenever he has trouble starting his car after a hot soak, he flips the switch to run the electric pump and he is then able to easily start his car.  The pumps he uses AC Model 6VER11 (6V) and 12V2401 (12V), which now appear to be long obsolete.  These pumps are solenoid operated and use a couple of check valves to allow flow-through operation.

The same things that work with newer carbureted cars (let's call them 12V cars) also work with older carbureted cars (let's them 6V cars). They include:

• insulating the fuel lines & shielding them from thermal radiation from the exhaust system
• adding insulation to the carburetor base
• adding an electric fuel pump

Insulating the carburetor from intake manifold heat will help hard hot starting because it will help to keep fuel in the carburetor bowl and to minimize poor idling from over-rich fuel mixtures.  You could stack some carburetor base gaskets together but too thick of a gasket pack might not seal very well and you might need sheet metal spacers interspaced between the gaskets to add stability.  Commercially available phenolic spacers for specific carburetors are not readily available for this limited market and they would have to be fabricated.  Some people have successfully used plywood as a spacer.  Measure how much hood clearance you have with putty or play dough before starting fabrication.

As with newer cars, do not disable the intake manifold heat control system (heat riser).  A hot spot under the carburetor is necessary for good drivability even if you live in Furnace Creek during the summer.  Your car may work OK without intake manifold heat but it works better WITH heat.  Keep the intake manifold hot and the carburetor cool.

If you're going to build your own phenolic carb spacer, sheets of phenolic resin are available in a variety of thicknesses.

Electric fuel pumps are available for 6V applications but the selection is much smaller than for 12V applications.  Most 6 volt pumps are solenoid rather than rotary vane (like the Carter P4259) so these pumps put a smaller electrical load on old generators.