Fighting a vapor lock problem. Application is '77 460 with a Holly 4V. No polution junk on the truck. Shut it down hot, let her sit awhile and she wont start till the carb is cooled. Cranks fast, battery good, just no fuel to the carb. Do the fuel line covering blankets work? Do clothspins or other "heat sinks" on the fuel line work????
thanks,
ray

 

I have heard that this problem has been overcome by putting a non-metallic spacer under the carb. This prevents the gas from boiling off in the carb when the engine is hot.
Although I am sure that fuel line blankets or heat sinks would help, I would be more inclined to reroute the fuel line away from the hot areas such as headers/manifolds, engine block, etc.
Hope you get it fixed.
Sparky

 

Sparky is right. After installing a 1 inch 4 hole spacer under my Holley 4 barrel I've had no more vapor lock problems.

 

hi Ray...

Couple of things: how do you know that there is no fuel in the carb? Have you pulled the top cover to expose the float bowl chamber and observed no fuel? (engine not running, of course). If this is the case, then you want to get to the bottom of it (pun intended) asap since the fuel is then matriculating down the intake manifolds and raw fuel is puddling up either behind the valves or in the combustion chamber as the engine is sitting/not running for some time--real bad news for the engine! If this is happening, check your accelerator pump cluster--it holds the accelerator nozzles and idle jets. If this cluster is loose, or the gasket that sits under it is damaged, fuel would leak past the idle jet passages and down into the engine.

On the other hand, if there is fuel in the float bowl chamber, and it simply runs out of fuel before you can get it running for a bit, it may be that the check valve in your fuel pump is damaged, in which case what is normally supposed to be a one way valve inside the fuel pump to keep fuel from going back to the tank from the lines, is malfunctioning. Pull the line going out from the fuel pump to the carb--at the pump-- after it has sat for some time and observe if there is any fuel that runs out. (watch your eyes--normally it is under pressure and will splash around once released). If there is no evidence of fuel under pressure, then it is most likely that the fuel pump has to re-prime itself every time you start it up (drawing from the empty lines that come from the tank) and this delay allows the float bowl to run out of fuel.

cw

 

I had the same problem on my 390 the fuel pump was just to weak to keep the pressure up to keep it from vapor locking. But if that is not the problem the line blankets do help and the spacer under the carb is a must for any vapor lock problem if not for this problem to pervent future problems.

Good Luck