any carburator experts?

[69me 10]

shouldn't the fuel bowls stay at the set level after the car has been shut off? mine seem to be leaking down and I'm smelling gas 30 minutes after I shut it off.  I think I might have trash holding the needle valve open. I have also noticed with the electric fuel pump on the bowls will fill past the setting until engine starts. any ideas?

[barnett468 418]

shouldn't the fuel bowls stay at the set level after the car has been shut off? mine seem to be leaking down and I'm smelling gas 30 minutes after I shut it off.  I think I might have trash holding the needle valve open. I have also noticed with the electric fuel pump on the bowls will fill past the setting until engine starts. any ideas?

 

 

it will definitely get lower the hotter your carb is especially with the alcohol in the gas because it evaps/boils at a lower temp temp than gas.

 

you may need a phenolic carb spacer and if you live in an area that does not get to freezing then you might want to block off the heat cross overs in the bintake also if you have them.

[TexasEd 191]

Is the gas leaking out onto the intake manifold?  Mine was and it turned out to be the accelerator pump rubber had rotted.

[moodster 55]

I had the same issue as TexaxEd with my Autolite 2100.

[SparkyGT 26]

what type of pump do you have, some of them can have higher pressures which may overwhelm the floats / needle

 

also is your pump on key on power i hope?  when shutting off, the fuel pressure will still be being pumped until the key is off.

 

you can also replace the needle/seat assembly.

[69me 10]

hey SparkyGT, the fuel pump is a Holley blue top, it is switched after the key is on so it can be cut off by key or switch. I do have a fuel pressure regulator which I try to keep under 5psi. I don't see any fuel leaking onto the manifold. the fuel pressure gauge drops to zero immediately when the pump is turned off. the carburetor is a summit racing brand 750 with vacuum secondaries . the carburetor is relatively new, probably less than 500 miles on it , not quite a year old. I have had some issues with the pump and regulator when it comes to starting the car. after it is running the pressure seems pretty constant.

[1969_Mach1 333]

Just my 2 cents on pressure regulators. I've never messed with fuel pressure regulators. But, from an engineering standpoint, I don't see how a pressure regulator without a return line will reduce fuel pressure if the motor is not running and fuel is not flowing through the lines and carb. In other words, I would expect the pressure to be higher than the regulator set point if the engine is not running and the fuel pump is on.

[Protowrxs 111]

I think I remember a busted power valve leaking on me years ago. Was a Holley but aren't the Summit's very similar? Just my two cents from what I may or may not remember. That would only cover the front bowl though I think as the rear usually doesn't have a power valve does it? Too long since I've been inside a Holley I guess.

[SparkyGT 26]

hey SparkyGT, the fuel pump is a Holley blue top, it is switched after the key is on so it can be cut off by key or switch. I do have a fuel pressure regulator which I try to keep under 5psi. I don't see any fuel leaking onto the manifold. the fuel pressure gauge drops to zero immediately when the pump is turned off. the carburetor is a summit racing brand 750 with vacuum secondaries . the carburetor is relatively new, probably less than 500 miles on it , not quite a year old. I have had some issues with the pump and regulator when it comes to starting the car. after it is running the pressure seems pretty constant.

 

before starting after it sits for a while, a day or so.  take of aircleaner, look into carb, you can move throttle and see if accel pump shoots some fuel from the squirters, if so you have fuel in bowl, also do you have see through sight plugs on side of bowl?  just check for fuel in bowl basically.

 

Just my 2 cents on pressure regulators. I've never messed with fuel pressure regulators. But, from an engineering standpoint, I don't see how a pressure regulator without a return line will reduce fuel pressure if the motor is not running and fuel is not flowing through the lines and carb. In other words, I would expect the pressure to be higher than the regulator set point if the engine is not running and the fuel pump is on.

 

from what i remember about hydraulics, a pressure regulator will bleed of extra fluid to the tank with a return, without one, you deadend the pump, which is why holleys are noisy, you can plumb a return back to tank or one to the carb only. on the opposite side you can put a pressure gauge to see the output like this  

 

 

I think I remember a busted power valve leaking on me years ago. Was a Holley but aren't the Summit's very similar? Just my two cents from what I may or may not remember. That would only cover the front bowl though I think as the rear usually doesn't have a power valve does it? Too long since I've been inside a Holley I guess.

 

 

to check power valve.  put your finger and plug the front fuel bowl air vent while running engine, if the engine dies, the power valve is ok, if it keeps running , it is sucking fuel through the power valve. you are creating a vacuum which will stop fuel.

 

[SparkyGT 26]

also this  plumbing can be used