fuel coming out the vent tube


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By drof75 - 13 Years Ago
I am really weak with carbs. So I need some direction. When I start the car, running real rough, there is fuel coming out the vent tube on top of the carb. It's a holley 1850 600 cfm. My guess is the float is stuck in the down position. Any input as where to start would be great.
By Pete 55Tbird - 13 Years Ago
Buz

Start simple. Take a plastic mallet or large screwdriver handle and TAP the side of the front and rear float bowl to try to jar loose the float. If that doesn`t work get some REUSABLE bowl gaskets and ask a lot of questions. Pete

By gekko13 - 13 Years Ago
More likely just a piece of debris in the inlet valve.  The other possibility is a float that has sunk.  The brass ones sometimes leak and the foam ones sometimes absorb fuel and cease to be boyant.  Once in a while you can get lucky and just rap the adjustment screw on the top of the float bowl with a screw driver handle and get it to seat and function properly.  Good luck.
By drof75 - 13 Years Ago
I got lucky. I was given a rebuild kit for the carb. I took off the bowl and found that the inlet valve was stuck open. I cleaned everything real good and replaced the valve with the one in the kit, put her back together and all is good. Is there an adjustment on the secondary's? They don't seem to be opening.
By bergmanj - 13 Years Ago
Oldcarmark,

To my (limited) knowledge, those vacuum-operated secondaries do not open on vacuum drop; they open on vacuum developed by the engine (with higher RPM's) below the throttle plates only when the primaries are wide open.  They open as the engine "asks" for more fuel/air mixture.

Someone, please correct me if I'm on the wrong path here.

Regards,   JLB

By Pete 55Tbird - 13 Years Ago
Buz

To test if the vacuum secondary operate use your ears. Take off the air cleaner, drive the car so that it will not downshift if equipped with A/T and floor the gas pedal. The noise from the air going into the carb changes pitch when the secondaries open. Like a moan. Pete

By Ted - 13 Years Ago
drof75 (4/12/2012)
....... Is there an adjustment on the secondary's? They don't seem to be opening.
The vacuum secondaries on the model 4150 & 4160 Holleys begin opening based on the air speed going through the passenger side (U.S.A. pass side) primary venturi.  There’s a small port just below the venturi that picks up the air speed signal and this pulls a vacuum to the secondary pot diaphragm.  There’s also another port located in the passenger side secondary venturi which bleeds off some of the low rpm vacuum signal to the secondary chamber.  This secondary port can be plugged making the secondary operation come in sooner.  Changing the spring in the secondary pot will also allow the opening rate to be altered to suit your needs.

 

Here’s the link to a past thread on how to bench test the carb to determine if the vacuum secondary operation is functional.

http://www.y-blocksforever.com/forums/Topic58952-3-9.aspx