srosscamaro@aol

just put a brand new crate motor in my 85 trans am with new everything water pump included a holley 600 and edelbrock intake and edelbrock headers and relized when i shut the car off the fuel in the carb is boiling what could it be ,i was thinkin i might need a phenlic carb gasket?oh and i have electric fans that run all the time and a cowl hood that i would think would let the heat out

A.Delaney

I have seen this happen with edelbrock carbs maney times, but never a holley. A heat shield under the carb solved that issue.

Whiteaw57

iTrader: (1)

i had that happen. i dont know it youre running a mechanical fuel pump on the side of the block but what happened to me was when i changed to AN hose right at the pump the hose was just barely touching the lower radiator hose. talk about vapor lock. anyway just moved the hose slightly and while i had it loose put a heat sleeve over it. cleared it right up

T.L.

Holleys experience the SAME problem. I don't know how true it is, but one of the Techs at Holley told me that today's gasoline has a lower boiling point than it used to, and that many people experience this problem. I even added a phenolic spacer (different car -- not my Third-Gen), but the problem persists...

Whiteaw57

iTrader: (1)

Id be sure that the fuel line into the pump isn't touching a hot spot somewhere, then be sure that the pump to carb line isn't touching a hot spot. If you still have a problem try to get some heat wrap for it.

Apeiron

What fuel pump are you using?

sofakingdom

iTrader: (1)

Try one each of these. http://www.cantonracingproducts.com/...&category=8510

The usual problem is that the fuel pump gets heated by the block, which heats the fuel, which then boils and spews when it reaches the carb and goes from 4 psi or whatever, to 0 psi.

T.L.

I think I'm gonna try that on my F##d. I never thought of a hot fuel pump as being the culprit...

sdowney717

todays gas evaporates and boils easily.
So keep it cooler by putting a plywood spacer under the carb.
Cut it to shape and then epoxy coat the wood.

Rubber fuel lines to carb also insulate fuel, go with marine grade for best for fire protection.

Mark@C&S

Hi my name is Mark and I obviously work for a specialty carburetor shop. To get to the point, it has been our experience the main culprit in fuel boiling is the lack of a fuel return systems. The stagnant environment with returnless systems, heat soak underhood conditions cause the fuel boiling. If you would like some specific suggestions to create a return system or any questions on carburetors, pm me.

Apeiron

sdowney717

returning the fuel should help keep it cooler in the lines, but wont do anything for the fuel in the carb itself. Use an electric pump and a bleed off regulator
so the fuel is constantly cycling back to the tank and the carb takes only what it needs.

What I would like to see is a closed carb fuel system venting system. If you could stop fuel evaporating out of the carb, It would help keep it cleaner and readily start it after sitting without fuel flooding the motor or the carb fuel totally evaporated. Fuel injections have an electric valve and when it is shut, fuel wont move or evaporate. What would happen if the bowl vents had an electric operated valve which somehow sealed the carb from the air when the engine turned off?
I think it must be possible to design. Sort of a carb that is like a TB fuel injection system, but is still a carb that does not need a computer.

sofakingdom

iTrader: (1)

The stock fuel system in these cars, if they came with a carb, includes a return, built into the pump.

If it was FI, the return is hooked up to the pressure regulator.

The OP didn't say whether he had "upgraded" (NOT) the fuel pump. If so, re-installing a stock one would restore the return system. If it didn't come with a carb, then using a stock carb pump and hooking the pump's return fitting to the OE FI return line would get it done; or, if he's converting from FI, using a 3-port regulator (Mallory 4309) would also restore the system to its proper stock operation.

Apeiron

Lots of emissions-era carbs have all kinds of features to capture evaporated fuel, including bowl-vent valves.