Holley 750 Vacuum Secondaries NEED HELP

[64SF]

Replaced the 750 Edlebrock with a almost new Holley 3310/ vacuum secondaries....noticeable difference but am having an issue with "dribbling" fuel in one of the rear venturies (passenger side) when I shut off the car. Creates a flooding issue on restart. I've attempted to set the float level and have it at the bottom of the site hole, pulled to rear bowl needle & seat and float appear to be OK. On a couple of float bowl adjustments I had fuel discharge from the vent tube.

 

[nm9stheham]

Sounds like you need to actually replace the rear needle and seat; it could have a hairline nick in it or is made off-center, allowing pressure to push fuel in after shutoff. That is clearly the issue if you have fuel out of the bowl vent after a small adjustment. Also, check what is riding on the needle to be sure somthing is not twisted or bent and hanging and pushing the needle sideways.

Is the float level right at the bottom of the sight hole when running?

This next step has some risk so don't do it if you don't like. Take out the sight plug when idling after a cold start, and then shut off the engine and see if fuel spills out; have an extinguisher ready!

 

[67 coronet]

just replace the needle and seat,then see what happens.sounds like it may be sticking real hard to tell when that is happening.but it causes what you are describing.

 

[Cranky]

Are you running a stock fuel pump? If the needle and seat are questionable, an aftermarket pump may be too much for it.

 

[64SF]

Stock fuel pump, tried needle and seat (Holley part) still dribbling, float looks good by may replace it just in case...will attempt to adjust again. Thanks for the suggestions.

- - - Updated - - -

Found this searching the web will try as well.


What you can do is with engine off run the needle and seat assy down until
the removable nut can barely engage the needle/seat assy.

Then put the lock screw back in and tighten. next start engine and run it for a few minutes to normalize the fuel level in the bowl, shut motor off and remove the sight plug on the side of the fuel bowl.
If fuel still runs out you have a problem with a bad float or leakage of or around the needle/seat assy that will have to be fixed first.

Now lean on the fender of the car on the side the sight plugs are if no fuel dribbles out/wets the threads of the sight plug hole then loosen the lock screw ( be ready for some fuel leakage around the screw if there is residual fuel pressure) on the needle and seat assy. and turn the nut 1/2 of a turn counter-clockwise ( if i remember right) then snug the lock screw.

Now start engine run for a moment and then lean on the fender and look for fuel coming out the sight plug hole again. If its still to low repeat the adjustment steps again until fuel dribbles a little when you lean on the fender once it does your good to go, close up the sight plugs and snug the lock screw again to make sure.

You can do the adjustment with the engine running but your going to have fuel spraying out when you loosen the lock screw and that can cause a fire

 

[747mopar]

Agree, replace seat but I'd check the fuel pressure first (should be in the neighborhood of 7psi).

 

[Meep-Meep]

Holley's have a terrible habit of that needle and seat O-ring leaking. You know, the one in the middle of the assembly.

 

[64SF]

May have found the problem....the photo shows the secondary metering plate gaskets. Note one hole is not punched through although it was "scored". I've ordered new gaskets from Summit ...not going to re-install or punch out the hole. Am thinking of sending it to Holley along with a letter sharing with them this has driven me crazy for over a week...I'll post the results when I receive the new gasket with all the holes open....by the way it connects to the same venturi that's been dribbling.

 

[coloradodave]

Good catch....love it when a solution finally comes to light.

 

[bm02tj]

When I rebuild a carb or any thing I save all the old parts and check new items as we all know sh!t happens

 

[64SF]

The new gaskets solved the "dribble" problem.

 

[67 coronet]

The new gaskets solved the "dribble" problem.

thanx for the info,thats a new one on me.holley say anything yet?

 

[Photon440]

Glad you got it fixed, although I'm not sure in my mind how too much gasket material caused a dribble...what am I missing?

 

[WileE]

Glad you got it fixed, although I'm not sure in my mind how too much gasket material caused a dribble...what am I missing?

Look closely at the top left of the brown gasket. The hole is not punched through. These are the passages in the carb, this one is blocked.

 

[64SF]

Holleys reply which is what was happening with the unpunched hole.

Hello,

Thank you for contacting Holley Performance Products. Common cause of that is a clogged idle air bleed.
The air bleed cuts the fuel signal off to the booster, if the bleed is clogged it can continue to syphon fuel from the bowl.

Spray some compressed air, or carb cleaner down the air bleeds.


Sincerely,
Colin Kinser
Holley Technical Service

 

[nm9stheham]

I just read this, saw the blocked hole (good catch, BTW), and thought 'air bleed is blocked'... and that is what Holley says. Makes sense.

BTW, the letter's description of what an air bleed does is not entirely complete; it describes what the air bleed does after shut-off. In operation, the air bleed jet allows air to come into the mixing (or emulsion) tube in the jet body from the top and the main jet feeds fuel in from the bottom. The air and fuel mix and produce an air/fuel emulsion (small fuel droplets suspended in air) and that is pulled through the auxiliary venturis and down the throat. Some carbs have changable emulsion tubes, and air bleed jets as well as main jets (not this one).

An air bleed change will typically cause a need to for a main jet change. So your secondary carb jetting/operation from heavy cruise to WOT will change with this being fixed.

 

[383man]

I have seen the clogged air bleed do that before but have not seen the hole in the gasket not punched. It will cause a siphon effect and cause the dripple out of the venturi. Nice that yiou found that because 99% of the time it is a float or needle and seat problem. Ron