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In a message dated 11/21/2004 8:39:48 PM Central Standard Time, finn.lassen@verizon.net writes:
<< I'm near wit's end trying to find out why I get bubbles in the line from my facet pump to my carburators.
>>
If in fact there are no leaks, the bubbles are probbably just boiling fuel. I had two things go wrong on the race car that sounded like that. One was the main fuel filter being big and made of aluminum would collect tons of heat. That got the fuel temp into the screw up zone, and until I added a blast tube to blow onto the header, the fuel in the float bowl would boil and run over rich at first, then run to lean cutoff, even with two MSDs. Later I discovered that the fuel pressure regulator was doing the same thing. It looks like it has a beach towel wrapped around it now. Fiber glass insulation. covered by silver tape. If the headers are stainless, put heat wrap on them. Make the heat shield two layers with an air gap between them. All of the air to the air filter comes from the center top of the grill opening. This is the highest pressure and coolest air supply.
Both pumps level with the bottom of the tank or lower. So here you go: pumps lower than the tanks. Pumps as close to the tanks as possible. Keep fuel pressure as high as possible all the way to the regulator, and the regulator very close to the carbs. Insulate anything that can collect heat. This includes the intake manifold and carbs, and intake air. Suction lines bigger than pressure lines. Are those Facet pumps the square vibrator type? Try a sliding vane pump, like a 7 PSI Carter (no Holleys please). I do use a Holley fuel pressure regulator. Fuel under pressure seldom boils. Fuel under suction (below 14.7 PSI) often boiles, and it gets much worse the higher you go, and worse yet with heat. You might entertain a bleed back. Where the the fuel line is TEEd at the carbs and then runs back to a tank through a restrictor, so that there is constant circulation, with the coolest fuel going to the carbs. Like the old stock Mazdas.
Not a big problem.
Lynn E. Hanover
Fuel System.jpg
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