I just put some higher flowing aircleaners on my two Stromberg BXOV-2 carbs and had to do a couple quick adjustments. I noticed a great improvment, but now was running out of fuel in the carbs as I was getting on the freeway, and cruising in the fast lane on the freeway. Any suggestions? I might switch to the four barrel intake, but would love to keep the motor looking early 50's period correct.

bigger gas tank???????? just kidding lol
check fuel float level, maybe need a little bigger fuel line or maybe fuel pump?

I'm with Larry on this one. You might check for partly plugged fuel line,kinked fuel line, dirty fuel filter, or fuel pump that isn't up to par. Run a "T" to a fuel pressure gauge which you can get at your friendly local auto parts store or Summit or Jegs and splice it into the fuel line between pump and carb, then check the fuel pressure with the engine running. Should be about 5 psi, give or take a pound or so. If that's good, then check for correct float level in both carbs and for dirt in the carb passages. And after you check the fuel pressure, disconnect the gauge and put the fuel line back together. And if you happen to be a smoker, for God's sake, don't smoke while you're doing this stuff.

Dear Cabbie;

You need to check the volume of the pump too. It should be 2-3".

The stock 5/16 lines/pump are okay for twin carbs. The 40-48 models (Chevrolet) had a 3/8" pipe from the tank to a 90 degree fitting reducing the size to 5/16. Sometimes this bend gets restricted. Some 30s models had 1/4" feed line which is to small.

Good luck.

I would agree with 64Novawagon, I had a similar problem once much like you're describing and through pulling my hair out, eventually discovered it was a kinked fuel line under my truck where the 2 steel lines came together with a short rubber line. the rear steel line had shifted and created a kink in the hose.

You didn't state the vehicle. I have found all of the lines too small on the Chevs I have had when adding multiple carburation when you get on it. Always feed the pump with as big a line as you can and check filters often. One other item is the air bleed into the tank. If the cap is sealed you may be having a problem there also. Good Luck

How do you know that the carbs ran low on fuel? You may need larger jets with the less restricted air cleaners. Too carbs shouldn't require significantly more fuel than a single, and no more than a single at cruise.

At cruise the carbs drove fine, even right after I got off the freeway. I dont think it is jets because it was dropping flat on its face then jump back up to normal. almost like a water hose that gets pinched and opened, and then pinched again. As soon as I came back down to a cruise all was fine. The motor is a Chevy 235. I dont know what size the lines are, but they are stock 54 belair lines. On the carbs the mains are #58, and the high speed bleeder is #64. The power bypass is #56. The fuel cap it definatly not sealed since the rubber ring is missing, and the auto parts stores around here dont have a cap that would fit my car, believe me, I have tried to replace it.

C;

If your pump's 'feed line' is clear, you need to fully test (3)** the pump then the output lines/filters. In that order.

I would guess that the pump is failing as; it was all fine before the air filter switch.
This assumes the new filters aren't restricted in some way.

Good luck.

** A mechanical pump MUST: have proper volume & pressure (2). It also needs to hold the pressure too (3). Crank the engine (Ing off) & read pressure, it should stay there when you stop cranking for 30-60 sec.

I agree with John ,might be a faulty pump.From my experience with V type engines,a 5/16 line is adequate to provide fuel for 300 hp if the pump is capable of 6 psi.I have a 302 GMC making about 240 hp that has no fuel issues,3/8 line on the suction side of the pump,5/16 line from the pump to the carb.The fuel pump is a generic 235 Chevy unit with about 3-4 psi at wide open throttle.

My problem ended up being a restrictive fuel filter. I pulled the fillament out, and all is good. Now I need to find a vintage looking high flow fuel filter.

Dear Dan;

The 'orginal type' fuel pump (glass bowel) has the filter built in etc.

In 1955 (passenger cars) AC pumps were made W/O it & there was a cover plate there in It's place.

The truck supply places have them & their made in Canada. They have the line (pump to carb) too. Look for the 1957 1/2 ton replacement.

Good luck.