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What can cause a 1953 commander 232 v-8 engine to vapor lock or stall at low speed?

The early v-8s with their high-mounted fuel pumps and six-volt electrics offer the greatest challenge for restarting a hot engine.

1. The ignition system needs to be checked to make sure it is providing spark to the plugs when the engine won't restart before looking at the fuel system.

2. Vapor lock occurs when the fuel begins to vaporize before it is actually distributed by the carburetor, usually because it has been overheated somehow. Try to cool everything down. Start by installing an insulator block or stack of base gaskets under the carburetor. Thickness is limited by hood clearance, but even a little bit helps.

3. Make sure the fuel lines aren't touching hot parts of the engine, and wrap them with strips of that shiny metal duct tape or fiberglass tape. Try running a flex hose from behind or under the grill directly to the air cleaner.

4. Check the heat riser valve at the outlet of the right exhaust manifold. The weight should be resting in the up position when the engine is cold and in the down position when the engine is at operating temperature.If it is not operating correctly It will continue to force hot exhaust gases through the intake manifold passage under the carburetor and cause the fuel to percolate in the carburetor. it will need to be replaced.

5. Coolant being expelled through the radiator overflow tube during idling indicates that cooling system maintenance is needed. Install a 160 degree thermostat and check the radiator cap to make sure it will hold 7 PSI. If the engine temperature seems to run above the normal range, have the radiator cleaned and tested Proper coolant level for vehicles without a coolant recovery tank is an inch or two below the filler neck.

6. Remove the three soft plugs (also called freeze plugs) on both sides of the engine block. Clean out the block internally through those holes using hand digging with strong bent wires and high pressure washing. Bent coat hangers work fine for this digging.

7.  Make sure the radiator fan shroud is  in place for proper cooling.

8. Try premium gasoline or diluting the gasoline with diesel in a ratio of about 1 to 15.

9. Finally, test the fuel pump per the shop manual. Fuel pumps that do not pass all three tests (pressure, vacuum, volume) will contribute to vapor lock.  Also check the fuel pump push rod for wear, or binding / interference from any oil line fittings that tap into the stand pipe on which the pump is mounted. If you still feel a need to make modifications see the item below for adding a return line to vent vaporized fuel.