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As a test and temporary/permanant idea make up a pipe that runs short straight path from pump to carb over the centre of the rocker cover. This will eliminate a lot of the engine heat on the pipe. I did that on my 1968 GMC pickup truck but I went one step further. I ran the pipe from the pump directly over and up against the inner fender where it is cooler and then directly over the valve cover to the carburetor. With the junk Ethanol gas, the truck still vapor locks as before. I also replaced the fuel pump with a new AC fuel pump and that didn't cure the vapor lock problem either.   
The Mangy Old Mutt
"If It's Not Junk.....It's Not Treasure!"
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In reference to pulling the hand throttle. I think the fuel filter next to the carb is compounding the vapor lock problem. The gas is boiling in there as well...Pumping the gas pedal does not seem to get enough gas in the carb to start the car when hot. Pulling out the throttle does though.I need a consistent flow...Maybe I need to increase the idle?
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ChatMaster - 25,000
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When starting the engine the only thing that counts is the fuel in the bowl of the carburetor. If the bowl is full the engine will run even if the gas line is disconected from the carb.
For starting the problem lies in the fuel bowl. If the gas in the bowl is spilling into the intake manifold thus flooding the engine or evaporating due to the heat.
Gene Schneider
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I installed a electric fuel pump 2 years ago after stalling many times because of vapor lock especially in the summer time here in Arizona. Put on a carter fuel pump and haven't vapor locked since, may not be correct but I'm on the road and not parked on the side of the road. 
p.k.
1956 BEL AIR 2 DOOR HARDTOP
I've spent most of my money on Booze,Women and mechanical things. The rest I just Wasted........
Remember , I'm not Always Right. But I'm Never Wrong !
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Tech Advisor ChatMaster - 25,000
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On my 1968 GMC I also installed an electric fuel pump. I installed the pump down on the frame rail behind the truck cab where it is cool, and now when my truck starts to vapor lock, I hit a switch on the instrument panel to activate the electric pump and away we go! I use the mechanical fuel pump most of the time and I only switch to the electric fuel pump when the truck starts to vapor lock. In the good old days when we had "real" gas here in Oregon vapor locking was not an issue on my vehicles.
The Mangy Old Mutt
"If It's Not Junk.....It's Not Treasure!"
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Gene is 100% correct. Vapor lock is the change of state from liquid to vapor due to heat and reduced pressure. Gasoline with ethanol has a higher vapor pressure than without it so is more prone to vapor lock. Increased resistance between the fuel in the tank and fuel pump can also cause fuel to vaporize in the line or pump. Gasoline in a carburetor can also boil causing first a rich condition followed by lean. It is rare in a running engine except for extended idling or climbing steep grades where the heat buildup under the hood heats the carburetor. It is more commonly when an engine is stopped and then the heat remaining in the block causes the carburetor gas to boil. It is very rare for the gasoline in the line from the fuel pump to carburetor to vaporize as the pump creates pressure that reduces the tendency to change from liquid to vapor.
How Sweet the roar of a Chevy four!
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Well said 
Gene Schneider
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Go ahead and try what Chipper suggested. Dump 1 1/2 to 2 gallons diesel into 13/14 gallons of gas and see what happens. After all, your heat spell will pass someday.
Good luck!
Russell #38868
'48 4 door Fleetline
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The Boss's '31 Fire Truck has a tendency to vapor lock when in a parade and temperature over 90 deg. She got tired of opening the hood pouring cool water on the fuel pump. Adding 10-15% diesel to gasoline helped a lot. Adding an electric pump between tank and mechanical pump totally eliminated the problem when the pump was switched on for a few seconds. Wrapping the fuel line before the mechanical pump with aluminum foil to better cool the line can help as well.
How Sweet the roar of a Chevy four!
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Chipper is correct in that the pipe after the pump is pressured it will only be up to 7lbs maybe a little more with a new and fresh diaphram. Prior to ethanol fuels I have seen several (not Chev) vapour lock until the pump to carb pipe rerouted or wrapped in heat insulation material.
Tony
1938 1/2 ton Hope to drive it before I retire
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All great ideas...I may be able to live with it until it cools down a bit...After all I live in the northwest...It won't stay hot too long
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I will gladly swap my daytime top of 50f for no more than 85f especially when I am working outside most of the day.
Tony
1938 1/2 ton Hope to drive it before I retire
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I will gladly swap my daytime top of 50f for no more than 85f especially when I am working outside most of the day. You have a deal and I will definitely trade!! I would much rather work outside in a 50 degree temperature than when it is 85 degrees.
The Mangy Old Mutt
"If It's Not Junk.....It's Not Treasure!"
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 98 today, 100 tomorrow here in south Georgia USA. Need your zip
Russell #38868
'48 4 door Fleetline
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very cool today.its 70 now. Will make it to 88
98003,Federal Way WA.USA
Last edited by chef-chevy; 07/09/15 01:52 PM.
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I never really liked the hotter climate but arthritis tells me I no longer like the cold either. If I could even it all out 85 would be my choice.
Tony
1938 1/2 ton Hope to drive it before I retire
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