Im a bit of a newbie when it comes to carburetors, so dealing with problems as they come is always a learning experience.

I've got an electric pump wired on a manual switch going through a mallory 4309 regulator to a Holley 650 DP.

Usually when i crank the car while it's hot, it will either just crnak and crank and not do anything, or it will crank immediately and run for 5-10 seconds and die and then it will crank and crank and not do anything. This has left me stranded more than once. Generally I just waste an hour or two and come back to it and it will be fine again.

Well yesterday it happened again. Car just wouldn't start at all. So I went ahead and popped the air cleaner off and noticed the carb was just dumping fuel sporadically through the squirters, tons of vapor out of the horns, and I even had fuel bubbling out through one of the small openings on the side of the venturis (at the top of the carb, not sure what they do, I though they were air bleeds of some sort but Im not sure. ).

My fuel pressure gauge was reading very low, 3 psi, and I've got fuel just sporadically squirting out the carb, so I went ahead and turned off the fuel pump, came back to it 5 minutes later and this time I left the fuel pump off (I normally switch it on right as I crank it) for a minute and the car acted like it was flooded but I was able to hold the pedal to the floor until it cranked (a tip a buddy gave me on starting a flooded motor, it never worked before, and I think I see why now, but when I turned the fuel pump off the constant fuel dumping ceased and it actually rectified the problem) and it ran without a hitch after that. Apparently when its hot, if I turn the fuel pump on, it's just going to dump tons of fuel into the carb. I even had puddles pooling on the throttle blades yesterday. Soon as I turned off the pump, it stopped.

Now that I'm aware that I have an actual problem, I went ahead today and switched on my fuel pump to replicate the problem, and of course, it does nothing out of the ordinary at all. I see no fuel bubbling out or squirting out of anywhere, and my fuel pressure gauge is reading 5-6 psi where I set it, not the 3 psi it was reading while it was doing this yesterday. And I realized, I neverh ave problems starting it when its cold. It's only when it gets hot that it does this weird business. I was thinking maybe the fuel was somehow draining out of the carb and that's why it would die so suddenly when I fired it hot, but now I've realized that it's just flooding out each time.


Now all of these pieces fit together to mean something, I'm just not experienced enough to know what it means. I'm not sure if this has something to do with vapor lock, or whether my fuel pressure regulator is intermittently going haywire or what... but I was hoping you guys might have some idea.

I was thinking maybe a float was stuck or something... but that doesnt even make sense, since it works just fine when it's cool?

 

Sounds like the fuel is boiling in the carb when hot and sitting.

 

That thought crossed my mind... but why would that happen? How could I prevent it?

Now Im thinking... my fuel line runs right over my valve cover. It touches the valve cover... now I'm wondering if THAT is the problem.

Any good ideas for a heatshield? I was thinking about wrapping it with insulation, but I'm not sure that would help much since it's still actually touching the valve cover. Or will it? Any recommendations on what to use?

 

If the exhaust is close to the lines, they will get hot. Are you using a return line?

Insulate the line where it touches the valve cover, that will get hot. You can also use a plastic carb spacer to insulate the carb body from the manifold heat