Holley 3367 pushing fuel up through the front vent tube

[Joseph I.]

I have a 66 Roadster, with a Holley 3367 carb. Last week while driving it just stalled out sounded like I just turned the key off. I pulled the air cleaner and there was fuel flooding everywhere. I soaked up the fuel, waited till it was cool, and turned it over. The fuel was gushing from the front vent tube.

I pulled the carb and did a carb rebuild kit. At first it did it flooded again, so I pulled the carb back off and re adjusted the floats. It started and ran perfect.
Today, I pulled the air cleaner off and started her up. She idled perfect. I took it around the block, and still ran perfect. So I decided to take a further ride. I drove about 2 miles, and it stalled out again, doing the same, gushing gas from the front vent tube.
Can anyone suggest what I am doing wrong, or what is causing this issue? Could it possibly be a bad float???????? I also found a couple droplets of water in the gas when I drained the carb after pulling it off
Any help would be GREATLY APPRECIATED !!!!!!!!!!!!!!!!!!!!!!!

[Bill M.]

Re: Holley 3367 pushing fuel up through the front vent tube

Check the needle valve and seat there might be a
Piece of grit causing fuel to flow by flooding the bowl

[David H.]

Re: Holley 3367 pushing fuel up through the front vent tube

Joseph

Any recent changes in your fuel system?

Dave

[Joseph I.]

Re: Holley 3367 pushing fuel up through the front vent tube

just replaced both needle valves.

[Joseph I.]

Re: Holley 3367 pushing fuel up through the front vent tube

No changes. Everything was perfect. Car was running strong, no issues at all. I did rebuild the carb after the first break down. Getting ready to pull it again and see if possible issue with the float.

[David H.]

Re: Holley 3367 pushing fuel up through the front vent tube

No changes. Everything was perfect. Car was running strong, no issues at all. I did rebuild the carb after the first break down. Getting ready to pull it again and see if possible issue with the float.

Joseph

Some other things to check at:

https://www.youtube.com/watch?v=rjoQvLNQ_d8

Dave

[Joseph I.]

Re: Holley 3367 pushing fuel up through the front vent tube

Thank You Sir!

[Bill B.]

Re: Holley 3367 pushing fuel up through the front vent tube

Joe,

Outside of my wheelhouse of expertise, but wondering if possible for the fuel pump to intermittently not regulate the fuel pressure to 7 - 8.5 psi. Too much fuel pressure could overpower the float/needle/seat and push fuel past the closed needle if there was enough pressure. However, if only the primary side is overflowing, and not both pri and secondary sides, one could argue against the fuel pump over pressure as a cause, given that only the primary side is reported overflowing.

[Joseph I.]

Re: Holley 3367 pushing fuel up through the front vent tube

Thank You for responding.
I have a fellow coming over this weekend to do a pressure test. Several guys seem to think that could be the issue.
I also purchased new floats, and new needle valves & seats, I was told just because I replaced them with new valves, the new ones could be defective.
My issue seems to be isolated to the primary bowl. When I pull the carb, the secondary always has fuel in the bowl, but I do not see gas flowing out from the back or secondary vent tube. .

I really appreciate all the help I am getting, and I will get to the bottom of this issue with all your help.

[Kenneth F.]

Re: Holley 3367 pushing fuel up through the front vent tube

Joseph, I have a '66 with a 3367 carb. I had rebuilt the carb a year or so ago, and it had worked fine the few times I ran it since the rebuild. A month or so ago, the accelerator pump discharge valve was stuck. Fuel coming out of the front bowl started soon after the accelerator pump problem. The float tested good, I cleaned the float valve even though I could not find dirt, etc. I still had fuel coming out of the vent. I removed the front bowl and noticed the o-ring on the float valve was no larger in diameter that the valve housing. I assume the o-ring had shrunk and fuel was by passing the valve.
I then started to examine the fuel in the tank. It looked darker than what I would have expected and smelled a little like paint thinner. I removed the old fuel in the tank and flushed the line. Everything good since.
We are both fortunate to have not had a fire.
Ken

[Joseph I.]

Re: Holley 3367 pushing fuel up through the front vent tube

Ken,
I will look at the accelerator pump, and replace the diaphragm, I have an extra new one. My tank is new, and the gas is fresh, but I will look again to see if anything made its way in recently. I did change the fuel filter element when I did the rebuild.
You are 100% right about a fire. The engine was hot, and the fuel was literally boiling on the manifold. I mopped up the fuel with a towel I use on my rear window when I put my top down. I do carry a fire extinguisher, and had it out. I was scared to death.
Thank You for the input, I will try and see what happens

[Timothy B.]

Re: Holley 3367 pushing fuel up through the front vent tube

Thank You for responding.
I have a fellow coming over this weekend to do a pressure test. Several guys seem to think that could be the issue.
I also purchased new floats, and new needle valves & seats, I was told just because I replaced them with new valves, the new ones could be defective.
My issue seems to be isolated to the primary bowl. When I pull the carb, the secondary always has fuel in the bowl, but I do not see gas flowing out from the back or secondary vent tube. .

I really appreciate all the help I am getting, and I will get to the bottom of this issue with all your help.

Joseph,

What type of fuel pump is on the engine now and how long has it been on there.

If it's a mechanical pump the pressure is set by the large internal spring mounted above the pump diaphragm, it should never increase pressure.

It is possible to have a spring that delivers higher than normal pressure, Holley carbs like between 5-6lbs.

[Mark E.]

Re: Holley 3367 pushing fuel up through the front vent tube

Do you intend to keep this car awhile? If so, consider getting a spare Holley (and distributor) for troubleshooting and tuning.

It's handy to have around and can save time.

[Joseph I.]

Re: Holley 3367 pushing fuel up through the front vent tube

Ok, so after rebuilding the carb, and breaking down on a test ride again I finally found the root of my problem.

After setting the float for the 6th time, fuel kept flowing out the front vent tube. I immediately pulled the carb, and pulled the front bowl. I noticed the float assembly, where the arch closes the needle to cut off fuel, was not hitting the needle, hence never shutting off the fuel flow. From my limited experience I felt there must have been a spacer between the c-clip and the float assembly on the pin that the float assembly rides on. I pulled the clip and removed the float assembly to find the pin itself loose. The pin pulled out of the bowl with just my fingers. I cleaned everything and reset the pin, and taped it down lightly with a small hammer. It seated firmly. I reassembled the float assembly and adjusted the float. Reassembled the carb, put it back on and fired her up.
Worked, no fuel out the vent. check the float through the viewing hole, perfect height.
All back together, no leaks and running good, maybe a little rich. My next quest is to learn how to adjust the carb.
PICTURE BELOW IS AFTER I FOUND THE ISSUE AND REASSEMBLED. Just to reference what I was attempting to explain above