Thread: Fuel vent

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I agree we are getting away from the issue------However---------if the needle is pulsating on the regulated side--the regulator is working very good.
A 950 Holley has pretty big needle and seat openings and hard to control higher pressure settings-they won't do good at holding over 5 pounds and as heat builds up in those lines the captured fuel above that regulator will "hydraulic" into the float bowls, overflow thru the vent tubes and leak out the throttle shafts spilling already hot fuel onto the top of a hot engine---------can anyone say car fire?????????

This fuel delivery system needs to be redone from fuel cap on the tank to the carb-


If needle is pulsating on the regulated side----the regulator ISN'T working very good---------

Originally Posted by 36 sedan

IMHO, the power valve's vacuum rating only relates to when the valve opens and would not cause a gas smell. Also, unless the valve's diaphragm is ruptured, the higher vacuum valve should not cause a rich mixture condition, but rather a momentary lean condition under power. The lower value valve will help eliminate a stumble under hard acceleration.

Sorry I gave you bad advice!
I got the power valve backwards. The power valve is normally open, it is held CLOSED by vacuum. So yes indeed if your power valve value is higher than actual vacuum it can and probably will flood the motor! While it only works while the engine is running, this still could be the reason you are smelling gas! Installing the correct valve may fix this! Sorry for miss direction.

I agree we are getting away from the issue------However---------if the needle is pulsating on the regulated side--the regulator is working very good.


If needle is pulsating on the regulated side----the regulator ISN'T working very good---------


Sorry Jerry but I gotta ask what you were trying to say..

I put a 3.5 power valve in and the spark plugs dried up and look good ,but will it hurt wot performance over the 4.5 power valve , and didn't do nothing for fuel smell

Originally Posted by Ken1960

I put a 3.5 power valve in and the spark plugs dried up and look good ,but will it hurt wot performance over the 4.5 power valve , and didn't do nothing for fuel smell

Will not effect WOT. Vacuum closes the power valve, WOT has no vacuum so power is open suppling the extra fuel needed to overcome vacuum drop. Now with the correct power valve, the motor has enough vacuum at idle and cruise to close the power valve and stop flooding.

After you have run the car a while and shut it off for a couple of minutes do you have to crank the motor a lot to start it?

I HAVE DONE AN EDIT AND ANOTHER SEPARATE ANSWER BUT NONE APPEAR---------If the needle is pulsating/etc-----then the regulator isn't doing a good job-----------

Yes it a little harder to start

No choke assy on that carb? You probably need to give it a couple pedal pumps for extra fuel--------

Originally Posted by Ken1960

Yes it a little harder to start

The three most common conditions that cause hard starting after warmed up are, 1) floats set too high, 2) fuel pressure too high, 3) heat soak from the manifold.
If the floats are too high, fuel will spill out the vent tubes and flood the motor. If the pressure is too high, fuel will slip past the needle seat cause the bowl to overflow, spilling out the vent tubes and flood the motor. If the heat from the motor transfers to the carb (common with aluminum manifolds), it will boil the fuel in the bowls flooding the motor.

Any and/or all of these three will cause hard starts after warm up and excessive gas fumes (strong smell of gas). The floats are an easy fix, just re-adjust them a little lower and see if the problem goes away. The fuel pressure is another easy fix, just adjust regulator to 5# or a little less and see if the problem goes away. The heat soak requires a spacer rated for heat soak, usually made from plastic or wood.

I have experienced all three of the above symptoms before, and fixed them with the above methods. It's worth a try on yours.

Drove car today does good while fuel pressure stays around 5 # but after driving awhile when come to a stop it wants to stumble on take off and pressure is dn to 2 lbs , don't no why that pressure goes up and dn

Originally Posted by Ken1960

Drove car today does good while fuel pressure stays around 5 # but after driving awhile when come to a stop it wants to stumble on take off and pressure is dn to 2 lbs , don't no why that pressure goes up and dn

Pressure fluctuating like that would indicate either a pump failing or a regulator failing, seems to me.

I think my problem might be the vent no bigger enough, magna fuel said I need at least a 8 n for vent , all I have is a 1/4 vent line that might be why it is stumbling a little on bottom only,but might be why fuel pressure is up and dn , the fuel pump I have is a pro 500 suppose to be up to 2000 Hp pump .

What about a 200 shot put on my bb , does it wear a motor out quicker , I have never tried it before and problay won't but there are some boys around here gunning for me and my stroker motor , I don't think they got nothing for it .

Originally Posted by Ken1960

I think my problem might be the vent no bigger enough, magna fuel said I need at least a 8 n for vent , all I have is a 1/4 vent line that might be why it is stumbling a little on bottom only,but might be why fuel pressure is up and dn , the fuel pump I have is a pro 500 suppose to be up to 2000 Hp pump .

How about loosening the gas cap to confirm if this is the problem, just a thought

Sent off today for another fuel regulator , I turned key on today without it running just fuel pump was running and the fuel regulater just kept going over until it pegged the needle without car running , so I think that is what it is . I took it aprt it looked good must be something wrong with it that I can't see