Carburetor Issue on Rebuilt Engine

[Alan Winer]

Seeking some advise on what appears to be a carburetor issue. Newly self rebuilt 59 super engine. All new valves, springs, guides, P & C. On test stand it was running rough and when #3&4 plugs were pulled one at a time, there was no change in engine. Pulling #1 or 2 plug would stall the engine. Spark present in all 4 cylinders and plug wires are installed correctly. I did a leak down test and all cylinders are well in spec. Switched carburetor sides and the reverse happen...so carb related. The carbs are rebuild. On the nonoperating carb I re-cleaned all jets and passages and checked the float level.
There is gas accumulating in the cover tube from the accelerator pump cylinder (overflow?) and there is visible gas accumulation in the starter chamber as viewed from the top. The float valve does not appear to be sticking and the floats look good. Everything else seems correct.
I am perplexed, would appreciate any suggestions.
Alan

[David Jones]

Alan, you do not say whether or not you are using a synchronizing device to see if both carbs are sucking air. If the butterfly is not open at all then there will be no fuel for ignition. Also check the valve in the base of the accelerator pump reservoir. I have seen them stick and not allow fuel through to the pump jets.
My suggestions for what it is worth.

[Alan Winer]

Thanks David,
Both carbs where synchronized and they were drawing air. I did check the valve in the base of the accelerator pump cylinder and it was free. I was able to force gas through the accelerator jets.
Alan

[David Jones]

Alan, look for an air leak in that carb. That would be my prediction. One of the drilling plugs has fallen out.

[Ron LaDow]

There is a gasket between the float bowl casting and the throttle body. If it is reversed (easy to do), it cuts off the fuel in the idle circuit, and I doubt you've gotten beyond that engine speed yet.
I'm not understanding this:
"There is gas accumulating in the cover tube from the accelerator pump cylinder (overflow?) and there is visible gas accumulation in the starter chamber as viewed from the top. The float valve does not appear to be sticking and the floats look good."
Can you use any of the images here to explain?
http://www.precisionmatters.biz/backsto ... -power.php

[Alan Winer]

I will check the gasket, hope it's that simple. Will take photos to post.
Thx

[Alan Winer]

Ron,
I checked the gasket between the body and the throttle plate and it was correctly installed. Attached is a photo of where the gas is accumulating.
Thx,
Alan

[Ron LaDow]

Alan,
If you have gas in that cross tube, that is easily 1/4" above the proper float level. It should not be that high, and if it is, it should be leaking out of the air correction jets. Something is not right there.
And the gasket is positioned such that the bottom of the starter chamber communicates with the large opening in the throttle body?

[Alan Winer]

Ron,
I did not notice any gas coming out of the correction jets. I'll redo the carb rebuild over and see what happens. I am beginning to think perhaps an erratic sticking float valve. I have seen some with burrs sticking open and/or closed. This one seems OK but I will replace.
Alan

[Alan Winer]

Ron,
Carb issue has been on my mind all night. Can you think of a scenario where the gas would overflow the accelerator pump cylinder but not flow through the idle or main jets?
Alan

[David Jones]

Regardless of anything else, with the carb flooding it does not matter if gas is flowing in the mains or idle jets as those two cylinders will not fire. Fix the flooding problem and they will probably fire but you may want to check those two plugs as they could be getting fouled because of an over rich mixture.

[Dick Weiss]

Alan,

Make sure the float's pivot assembly isn't bent or out of line allowing the floats to contact the sides of the float bowl; Hold down the pivot assemly and use a small wire hook to raise the float(s) up and down--the clearances aren't very much, but the pivot assembly slop must be minimized.
Also, the bottom check valve and the float needle should be inspected for non-sticking.

Dick

[Ron LaDow]

First, David's right; fix what you know is wrong before imagining some weird occurrence.
But to answer your question, see here:

"A" is the rough fuel level, given proper adjustment.
"B" is the approximate height of the auxiliary venturi mounts, not a fuel-tight joint.
And then:

"C" is where you saw fuel, compare to "A" above.
"D" is the approximate C/L of the main and idle jets.
Look at those and I'm sure you can see what you are proposing is very unlikely.

[Steve Harrison]

Is your float a sinker?
Shake it when you take it out to see if it sloshes.

[Alan Winer]

Well,
I went through the entire rebuild procedure again: recleaned everything, all jets are the correct ones, gasket is positioned correctly, checked drilling plugs and unless I missed one they all seem tight, checked floats, float assembly and float valve. The float level was high and I adjusted that (perplexing because I checked it multiple times before....but). And the carb is being supplied plenty of gas.
Same result: #3 & 4 not receiving gas, gas is accumulated and filling up the starter chamber but now not in the cover tube.
When I spray starter fluid into the carb the engine picks up rpm and just smooths out.
I'm at a standstill here.
Thanks,
Alan

Ron-great cut away photos!!