The Stovebolt Site Forums The Shop Area Engine Shop 1-4 not burning ?????????

I can't get my 235 with dual model 94 carbs running like it should. Has Langdons HEI, today I was working
on it and decided to pull plug wires one at a time while it was running. All were getting spark but
when I pulled plug wire off 1-4 the car ran like always(even 1-3 at same time). I pulled 5&6 and it ran very rough. Pulled plugs and 1-4 very black 5&6 burning perfect. Why are the first four cylinders not burning properly??
I just don't know what to do.
thanks for your help

taylour,

Welcome to the Stovebolt. Sometimes you can find a perceived problem, even when it doesn't exist. It is not unheard of the pull a plug wire and not see a noticeable difference.

The question is, is the engine only hitting on 4 cylinders when it is running. Dual carburetor are tricky to sync and make run...this is usually the problem until the learning curve is achieved.

If you can drive the rig down the road, you would surely know if those cylinders weren't firing.

Is this particular HEI getting the voltage it requires. This style ignition is usually strong enough to fire even a super rich fuel/air mixture.

Don't focus on the ignition, concentrate of the carburetors. Make sure the intake manifold and carb bases are tight and leak free. More help is on the way.

Stuart

Try swapping the carb positions and see if number one and two run well.

I,m thinking the front carb is loading up & carboning up the plugs causing missfire.

Thanks for the help. What do you mean by loading up.
The front 4 plugs are black like to rich of a mixture, While the back two are a beautiful tan. How much fuel should be in the float bowl when you take the top of the carb? I don't really understand how the float should be set.

taylour,

The term 'loading up' refers to excess fuel...the carburetor is dumping too much fuel into those cylinders, and when it manages to burn, it burns very rich and leaves behind the sooty residue on the plugs.

The important float setting is called 'float height'. This is the distance from the bottom of the float itself to the base of the carburetor casting. Sometimes it requires the gasket to be in the equation. This procedure is done with the carburetor removed and split into pieces. It's hard to describe so I have linked a picture of it being done on a carburetor.

The linked picture shows a gauge being used, and the gasket in place...It's a hard procedure to cover for a first time carb adventure.

Your rig has unconventional carburetors on it as I recall. A float that is waterlogged, or partially sunk will cause your type of problem.

Do you have any friends that could help you troubleshoot and repair this problem?


http://chevy.tocmp.com/Rochester/9D7p13.htm

Stuart

taylour,

Are your carburetors Holley model 94 two barrel jobs? That's lots of carburetion for your rig unless it has additional work done to it..isn't it.

Stuart

I figured Ford 94s, the replacement for Stromberg 97s. If so, it shouldn't be too much carburetion.

They are ford 94s and I think the float may be the problem. I get gallons/mile fuel consumption. Maybe I
am dumping way to much fuel. I am replacing the intake and exhaust gaskets right now and tomorrow I will tackle the float issue. You all are awesome,thanks for all your help.

P.S. it is an edmunds intake and you cannot use the metal sleeves to line it up. Could that be a problem?

Check the power valve diaphragm in the front carburator. If those fail they dump gasoline from the float bowl right into the intake.

Uh, just read the post about metal sleeves.

Check for a vacuum leak. Low vacuum will trigger power valves to open and cause really rich condition.

I have always regarded the metal sleeves as merely a alignment tool, and not an attempt at sealing. The proper gasket should seal a flat manifold, ring or no rings..shouldn't it!

There is info out there that mentions exactly what Josiah says...torn or leaking diaphragms that dump raw fuel into the engine.

Stuart