Unwanted Pressure

[ojh]

Had a friend pull into the shop saying the engine was shutting off, the carb was wet in the front, all around the vent tube and fuel level out of sight in the glass. I had adjusted the float level last week. I gathered a new set of needle & seats thinking he had .130 and acting goofy on the street, he'd be better off with .110 or .120 for largest. I pulled the N&S screw & nut and fuel fountained up a full 1 1/2" then receeded. While we were staring in shock it did it again, not quite as high and eventually did it a 3rd time.
He has pretty simple and straightforward stuff, a new Shafiroff big SBC, new Holley Ultra Dominater, Holley blue FP, typical Holley regulator, -8AN from gas tank (vented, I opened the gas cap hoping to find pressure, alas, none present), -6AN hoses from each side of regulator to each end of the carb, engine temp was 180ish, intake was a tall brodix.
is there a check valve in the fuel pump so that fuel will be under pressure between Needle & Seat and the pump? Like the lines were gathering heat and the fuel pressure expanding? The -AN hose was the black stuff, not stainless braid or aluminum tubing. The gas is supplied out the top of the gas tank.
I suppose he could add a return from the pump outlet with 7psi checkvalve back into the tank? could run it from the front with a little bleed hole to create circulation?
Any thoughts?

[rgalajda]

Is this a bypass regulator ? Is there a return line from the fuel pressure regulator to the tank? If so, what is the fuel pressure set at?

[ojh]

No, not a bypass regulator & there are no returns. The regulator is the one that comes with the blue pump. Pressure is 7ish lbs on an older gauge that should be replaced. I do recall checking it a couple weeks ago when I set his float levels.

[Justa1time]

Good evening,

I just dealt with a very similar issue. I concluded the 10% ethanol fuel in my area would percolate at around 120ish °F- this is a hasty generalization measurement of temp with old laser gun.

Mine would push fuel up to top of sight windows after shut down. At times it would take 15 or so minutes for it to happen with my fuel cap also removed. I use a 4150 style carbureator and the fuel would push out of the 30cc accelerator pump well & bubble out the squirters also. Mostly on the primary squirter.

Solution?

I snagged a cool carb carb spacer with stainless fasteners. Cool carb mechanical pump spacer with stainless fasteners.

Routed braided hose from mechanical pump along block & head to passenger side of alternator then went up to fuel log- DO NOT RUN line between timing cover & water pump.

Dei heat sleeve on OEM 3/8" line that ran close to header and I havnt had a problem since. Knock on wood.

Bryan