3367 Carb issue

[Rob M.]

Ok, I've been messing with this for a long time. Looking for suggestions on what might be causing an apparent air leak. The carb is a brand new Holley 3367 (original is going out for rebuild) and it's sitting on a 66 Corvette 327/300 (original motor). The idle adjust screw can be closed and it still idles at @700 rpm. It can be stalled using the mixture screws which are set at about 1 full turn out. Checked the seal of the carb with the old spray-some-carb-cleaner trick and see if there's a jump in rpm but there's no leak there. Pulled the PCV line and plugged it - it only made a very slight difference. The vacuum advance was checked with a guage and it is functioning properly. The dwell and timing are both set to spec. The thing is that the secondary and primary metering valves are closed and yet it still runs. Any thoughts on what's going on?

Thanks in advance,
Rob 39795

[Dick W.]

Re: 3367 Carb issue

What about the secondary throttle plates? Are they open too much?? There is a stop screw to adjust the opening.

[Verle R.]

Re: 3367 Carb issue

As Dick said the secondary stop screw can hold the secondaries open too much. Also check the fast idle screw, it may need to be backed off a little. It can hold the primary butterfly open even with the choke off.

Verle

[Clem Z.]

with the carb off check if the butterflys are

centered in the baseplate bore,if not loosen the screws to center them.

[Gerard F.]

Re: 3367 Carb issue

Rob,

Of course you have probably already checked your checked your float level on the primary and secondary. If you take the carb off, also check whether all the air bleeds in the air horn are open, both on the primary and secondary sides. Try to blow air through them.

I had an instance where some were not even drilled, and had to drill both the air horn and the metering block. This could cause siphoning of gas into the air horn.

With a new carb, I think I'd take a long hot run, and then go through the adjustments.

I think the adjustment of the secondary stop is full closed and 1/2 to 1 turn open.

Jerry Fuccillo
#42179

[Rob M.]

Re: 3367 Carb issue

Dick,

They are closed and work just fine. We looked at them.

rob

[Timothy B.]

Re: 3367 Carb issue

Rob,

I have been chasing the exact same problem on my original 3461 AFB and I have changed a dirty fuel filter and now getting ready to change the needle and seat because the dirt may have damaged them. When I warm the engine and shut it off, the squirters for the accellerator pump drip gas which means high fuel level. The float level is set at 7/16" which is lower than the 5/16" setting in the service manual. Also wondering about the fuel pump and the repro overhaul kit/diaphram causing high fuel pressure so I am checking the pump pressure. I question all reproduction parts now-a-days including overhaul kits and gaskets. If this does not work the carburetor goes out to a pro because I have lost all patience with it.

[Clem Z.]

on AFB carbs check for leak thru the needle

seat gasket where it meets the float bowl cover. i have found that these gaskets have too big a inside diameter and do not seal. turn the top cover with the floats up and pressurize the fuel inlet with air pressure to about 6-8# and apply a soap solution to the gasket area and look for bubbles.if they are there that is your problem. the gaskets to seal properly must have to be "threaded" onto the needle seat and if they just slip over the threads they are too big.

[Timothy B.]

Re: on AFB carbs check for leak thru the needle

Clem,

I did exactly as you said and there is no leak at the gaskets. I am also wondering if the lead plugs on the bottom of the carburetor in the metering rod vacuum passage are leaking. What ever it is, it's very slight because the car does not flood, it just will not idle with the idle screw and the spark plugs show black and sooty.

[Clem Z.]

with the float bowl cover off set the main body

on a clean sheet of white paper and fill the float bowl cavities with lacquer thinner. leave it set for a while and if there is a leak tru it will show up on the paper as a wet spot

[Timothy B.]

Re: with the float bowl cover off set the main bod

Clem,

Did this also and no leak, the main body sat overnight and left nothing on newspaper but I can see why were constantly cranking these cars to start after sitting. Looked like half of the fuel evaporated out just sitting overnight.