1940 LaSalle and electric fuel pump

[z3skybolt]

Gents,

My previous 1940 LaSalle would seldom travel more than 10/20 miles without "vapor locking" thus requiring the use of it's add on electric fuel pump.  Cool or hot weather made no difference. Despite putting 3 different rebuilt mechanical fuel pumps on it the problem never went away.  The engine ran cool even during long hot drives at temps in the upper 90s.  My current LaSalle does not have an electric fuel pump.  I have driven it over 500 miles including long hot drives. It never "vapor locks" and starts instantly hot or cold.  It also runs cool under all conditions including when idling.  I use the same fuel in both cars....92 octane non ethanol gas.  So what is my problem?

Perhaps I am looking for a problem that doesn't exist.  But I know that other posters often struggle with this issue on their flatheads. I am considering adding a backup electric just in case.  What do you guys think?  Should I just stick with the mechanical pump solo until/unless the problem arises?  Any thoughts as to why this car does not have the vapor lock issue....so far?  I drove it 50 miles yesterday during 95 degree weather and several other times on hot days.

[V63]

There are many variables from cooling system effectiveness, fuel mixture and engine timing.

Those flatheads seem to accumulate a lot of crud in the engine block cooling cavities and, just guessing, one system was cleaner than the other?

[Tom Boehm]

Could your new car have wider fuel line tubing than your old one? Just a thought. When I was restoring the chassis on mine someone suggested using a wider diameter fuel line to help avoid vapor lock.

[wheikkila]

I would look at the size of the line. My 40 la salle never vapor locked. I did have problems with it boiling the gas out of the carb on hot days. I do have an eclectic fuel pump to help this situation. It would be interesting to know what the difference is.
Thanks Wayne   

[LaSalle5019]

I've never had my 1939 LaSalle vapor lock, but as Wayne mentions, on really hot runs the fuel will boil out of the carb a bit so to eliminate longer cranks, I just hit my electric boost pump during starts then turn it off.  It is nice to have that backup just for those occasions.