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Vapor locking 1965 ford mustang

i have a I6 200 1965 ford mustang coupe. when i’ve been out for a long drive, even on a mostly cool day (low 70s), if i pause somewhere, say in a drive through grabbing a drink, as soon as i get back out on the road, the car starts to stumble and will eventually stall. i believe that it is probably vapor locking. the car has no issue as long as i don’t take an extended pause in a parking lot anywhere.

my question is, am i vapor locking and if so, what can i do? the temperature gauge always stays in the normal range. is there any way i can shield the fuel lines and if so, with what?

To test for vapor lock pour cool water over the fuel line that runs from the fuel pump up to the carb. If the cars starts and runs normally after the water treatment you have pretty much confirmed vapor lock.

Vapor lock is both pressure and temp related. Since you are not reporting extreme temps your fuel pump maybe failing and not producing enough pressure. Higher pressures deminish vapor lock (which is why it is not an issue with fuel injected modern cars) and if this is a new problem it could be a sign the fuel pump is going.

The other solution to handling high temps is to wrap the fuel line with a covering usually metal. Check with your auto supply store (NAPA, AdvanceAuto, etc.) to see what they have and recommend.

I had a '67 Mustang (289 V8 w 2 bbl carb) and there was a small fuel filter that screwed into the base of the carb and the other end connected to the fuel line. The filter needed attention often. Check to see if the carb on your 6 has the same type filter set up. If it does, change the filter before doing much more. The filter could be affected by the heat and reduce fuel flow.

the cool water trick is a new one to me, but i see the point. i’ll give that a try.

i did forget to mention that the carb, fuel pump and filter all have less than 100 miles on them. the carb is not a rebuild but a brand new one i found online.

i do wonder if the problem might be with the cam that drives the fuel pump, if it is worn. the last guy who looked at the car felt it wasn’t getting enough pressure and replaced the pump, but the one he replaced had less than 1000 miles on it.

A problem I’ve seen on Japanese cars of the '70s is gas boiling in the carb itself.
Often they had the carb mounted to a non-metallic spacer for insulation.
Pull the air cleaner cover and look into the carb throat for gas bubbling in.
With the exhaust manifold right under the carb this is possible with he l6.

My 6 cyl '65 Mustang did not have any trouble in the 70F weather. You need to check fuel pressure, have a pressure gauge plumbed in right before the carb.

In 1965 you could buy 90 octane regular, pure gasoline, low vapor pressure…

Cures: An electric fuel pump installed back by the tank…
An insulating block between the carb and the manifold…
On your engine, check and see if the exhaust and intake manifolds are Siamesed together right under the carb. Is there any kind of a spring loaded damper between the two manifolds to control the heat??

Make sure there is not an exhaust or manifold leak that is hitting the line, and that the line is not against any engine parts.