C2 1966 Holley #3367 Flooding Secondary

[Bob E.]

Hi, I'm having an on going problem with the secondary fuel bowl flooding on my 1966 Corvette with a #3367 Holley carb. Car will run excellent but at any random time will cease to idle and die. Secondary fuel bowl will flood with raw gas dripping out of the rear boosters. Removing the rear sight plug screw shows the rear fuel bowl to be completly filled with gas while removing the front sight plug shows normal fuel level. I have chased this problem for a while.
I have replaced the metal float with a nitrophyl, it will happen with either float in it, numerous needle and seat changes, even tried a different rear bowl. I have surface sanded to perfect flatness the rear of the carb body and the metering plate and cover. The metal float is in it now and I have slightly bent the float mount bracket so the float sits as far towards the rear of the bowl with out rubbing on the bowl itself. I have installed a fuel filter at the rear of the car in the fuel hose between the sending unit and the main fuel line.
I think I've covered all the bases, but I can go out for a 90 mile drive and the carb will work perfectly but at some point I pull to a stop at a light and the car will not idle by itself, drive a few more blocks and all is good again.
The problem is always fuel dripping from the secondary boosters, never the primary. Fuel levels are set at the bottom of the sight plugs.
What simple thing am I missing to clear up this aggravating problem? It seems something is causing the needle and seat to not seal since the rear bowl fills to the top, but never affects the front bowl.
Any ideas?

[Rob A.]

Re: C2 1966 Holley #3367 Flooding Secondary

Bob,

I have the original #3367 on my '66. After removing the carb for an unrelated problem, I had the same problem as you after reinstalling it. I made NO changes or adjustments while it was off. I checked everything as you did. Then, I pushed the(original metal)float around a bit, I slid it towards the rear before putting the secondary bowl back on, and my problem was solved. I can't exactly say what it was that fixed it when I did that, but my problem was exactly like yours, and it was fixed after that. I believe you are correct that the only way fuel can spill out of the boosters is as a result of the needle and seat not closing. Considering my experience, I still believe it is related to the float getting hung up on something. I believe the tolerance must be very close between the float closing the fuel off and not. I know I haven't provided a solution, but thought I'd share this information.

[Gerard F.]

Re: C2 1966 Holley #3367 Flooding Secondary

Bob,

Agree with Rob. I had the exact same problem with a 67 3810 with the float hanging up on the secondary metering plate. Bent it back and made sure the pivot shaft was tight with no slop. Was amazed at the lack of clearance the brass float had against the metering plate or back of bowl.

If there is some slop in the float pivot, with braking it will move forward and then rub against the metering plate.

My idea would be to put the brass float back on, bend it back to the rear of the bowl with clearance, and make sure that the pivot is tight and cannot slide forward.

Jerry Fuccillo
#42179

[Bob E.]

Re: C2 1966 Holley #3367 Flooding Secondary

Thanks Rob. That's helpful information. I'll pull the rear bowl off again and try moving the float around. Knowing that you cured yours gives me hope. It has been a frustrating problem. I'll keep you posted on my progress. Thanks.

[Bob E.]

Re: C2 1966 Holley #3367 Flooding Secondary

Thanks Jerry, That's solid information to work with. I figured this had to have happened to others before me. Thanks for the help, I'll post when I try it out.
Bob #25835

[Bob E.]

C2 1966 Holley #3367 Flooding Secondary

I removed the rear bowl this morning and took the float (brass) out. I gently clamped the bracket of the float that slides over the float pin in a vise and gently pushed rearward on it until I could feel that it moved. Reinstalled it and made sure there was still clearance and the float would swing freely and not make any contact with the rear of the bowl. Put it back on the carb and rechecked the fuel level. I took the '66 out for a 45 mile drive on roads where I would always have traffic lights to stop for and did not encounter a single problem with stalling at idle when coming to a stop. I am very encouraged at this point. So far it seems the float just needed an another small tweak rearward. Hopefully this is the cure for the problem that has plagued me for a while now.
Thanks for the advice Rob and Jerry.

Bob #25835

[Clem Z.]

holley center hung float carbs with the plate

instead of the metering body uses the nitrophyl float because the fulcrum arm is shorter than the brass float. same for front and rear carbs on the 3X2 carb setup since they have plates not metering bodies. side hung floats both brass and nitrophyl should clear the plate unless something is bent or the float pivot pin in the float bowl has come loose and allowed the float to move forward. also make sure you have the float spring in place because engine vibration will cause the float to bounce around and cause flooding