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Fuel out the Vent tube

1695 Views 3 Replies 3 Participants Last post by  Ryan74
So, I have a 402 BB with a Holley 6310-3 carb. Just rebuilt the carb. When I hook up the fuel pump( mechanical) I have fuel coming out of the front vent pipe. The foot isn't sticking( brass) or filling up. I think the problem is I bought a fuel pump on eBay that came of a bb and the guy couldn't tell me the gph on it. I'm. thinking it's a 80 or 120 gph. So I got a regulated and I'm gonna install it on my day off. Open to thoughts on this issue. Is the regulated set properly gonna fix it or is something else amiss?
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Fuel coming out the vent pipe means only one of two things: Either the needle and seat are not stopping the fuel when the bowl fills (defective needle or seat), or the fuel pressure is greater than the needle and seat can stop. Either way, I agree that a fuel pressure regulator would be a good first place to start. I assume you set the float height correctly when you rebuilt the carb. Too high a float setting could produce the same outcome( see reason #1). Good luck!
I had the identical problem but it only happened every now and then.Fuel pressure would shoot up to 10-12 LBS and overpower the needle/seat, gas would puke out the vents into the carb and stall the motor.Installed a regulator and fine ever since.I'm assuming the regulator you have is adjustable so throw a fuel pressure gauge in line while you're plumbing in the regulator and you can set yourself up at 6-8 LBS with no guessing involved.If the problem persists you know it's the seats.A regulator is good idea regardless if it solves the problem or not.My pump was supposed to be internally regulated but was faulty I guess.One other thing I had happen was when I installed jet extensions on the secondaries and reinstalled the float bowl the jets would bite into the dangling foam float just enough when the bowl bolts were tightened to stop it from raising when the pump started so fuel would flow out the vent tube.Took a couple hours to figure that one out and had the bowl off 3 times before I spotted it.Installed the bowls with the carb upside down on the bench and all was good.
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Thanks for the input guys.
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