As it has started to heat up in Florida, my car is beginning to boil the crap out of its fuel. It's getting so pressurized within the carburetor that fuel shoots out of the boosters when the engine is off, filling the intake runners with gas.
My fuel filter is currently held horizontally over the intake manifold, I think it is too close to the hot thermostat housing and generally hot intake manifold. I believe I could move it so that it is vertically placed coming right out of the pump. However I am still nervous about my engine bay temperatures. Could I instead run it coming right out of the fuel tank? It seems like that would be the coolest area to have it. Bearing in mind that I have a mechanical fuel pump, could I put the filter back there and not have to worry about vapor lock? The fuel pump is new and strong.
Thanks for your help,
Daniel

 

I should probably mention that the 91 Octane fuel I'm running is up to 10% ethanol, which obviously makes the fuel boil at a lower temperature. Are there any additives to lover the boiling point, ethanol-free gas is hard to find around me?

 

You're on the right track with putting the filter on the inlet side of the fuel pump. Many folks install it in the short section of rubber hose between the metal line along the frame rail and the fuel pump. It's visible and easy to access.

Also make sure the fuel line between the pump and carb has as much clearance as possible between the intake, thermostat housing, etc.

edit:
as for the ethanol fuel, we have it here in Phoenix, too, and it's not an issue for me in the 110+ summer temps. Gasoline is blended so the vapor pressure is suitable for the geographic area where it's used, meaning the blend in Phoenix is very different than the blend in Minneapolis.

 

What is your fuel pump pressure? Have you checked your float level? Too high of a float can cause the same thing. Doubt its the fuel filter or gas.

 

I would've though the float height was too high, but I can hear the fuel gurgling and boiling in the float bowls.

 

The fuel filter is actually touching the thermostat housing ...oops. I'd imagine that's a pretty quick way to heat it up to boiling temperature.

 

If you don't mind my asking - what year, model vehicle, carburetor and engine are we talking about?

 

It's a 1965 F85 with a low compression 330. Carb is a holley 650cfm aluminum with vacuum secondaries.

 

Clean your float bowl vent.

 

Where is the level of fuel in the site plugs? If it runs out when you remove the plugs the level is too high and causes the issue your having.

 

I agree w/ you it isn't fuel or the filter - it's something a muck with the float. I was coming from the point of view the OP saw this happening after he turned off the engine & fuel continued to be sucked in. That can happen when the float bowl vent is plugged - it's like an internal vacuum continuing to suck in fuel instead of venting correctly.

 

Daniel, if all else fails and you would like spare 2 barrel Rochester for parts or a rebuild. I have one in great shape for FREE..Just pay for the ride from Dallas to Florida...Came off my 64 F-85 low compression 330 that ran good at the time 7 years ago....

 

Part of how I cured my boiling/hard start problem was to plug off the heat riser crossover. It's a huge heat source. I chose to weld cast plugs into the cast intake, eliminate the thermo flap in the exhaust mani. and disabled the heat stove on the passenger side too. Also added an insulator gasket under the carb. These steps completely eliminated the problem.

Set the carb float level 1 to 2 32nds lower than the spec.
Verify the tank is venting properly. Is the correct gas cap on the tank.
Crack the gas cap when it's hot to see how much pressure is built up.
Verify the needle and seat is closing off the fuel at rated pump pressure.
Verify you are not exceeding 6.5-7PSI...5 to 6 is preferred.
I do not run ethanol fuel is any carbureted machine.

I do not recommend putting a fuel filter on the suction side of a mechanical pump system.

All of the mods above cannot be seen visually unless you look hard at the carb gasket.

A big plus to the crossover plugs is, no more burnt paint on the intake(or discoloring on an aluminum). I did this 15 years ago intake still looks freshly painted.

 

I will be checking the float level today, I am also going to move the filter to a vertical position near the fuel pump outlet. The car has a 1 inch phenolic spacer on the carb, so I believe the fuel is being heat soaked before entering the carburetor(probably where the fuel filter is touching the manifold).

 

Relocating the filter away from the manifold has fixed the issue