Backfiring Engine

[Bill K]

I have a stock 1600 dual port with a single pic 30-31 carburetor. My car would run great, and then suddenly start backfiring from the right bank. It sounds like the kind of backfire that comes from unburnt fuel exploding in the exhaust header. The header for that bank also always looks a lot blacker and sootier than the left bank. Also, the #2 plug is always a lot blacker than the other plugs.
I assumed an ignition problem so I replaced the entire ignition system including distributor and down to new plug wires. It ran like a champ, and then once again after a bit of driving, it started backfiring from the right bank .
So, this morning I tried disconnecting the plug wire to the #2 cylinder, and the backfireing would stop --- reconnect the plug wire and the backfiring would start again.
I then replaced the #2 spark plug, and it ran fine, but I'm reasonably certain that it will start backfiring again after it's been driven a while.
Thus it appears to me (and that is just my very amateur opinion) that for some reason the engine is fouling out the #2 plug from being too rich.
I'm going to do a compression test tomorrow, and check the valve clearances, and will post the results when I'm finished.
In the meantime, if what I've given is enough to diagnose the problem, I sure would like to hear what it may be.

[Bill K]

I have 125 psi compression in all four cylinders.

[MURZ]

thats good!

[David O']

What kind of spark plugs do you use?

[Bill K]

I think I've used them all -- Champion, Autolite, Bosch, and currently NGK's.
In NGK I used the regular heat B6HS, and even tried the hotter B5HS.
After checking the compression I again checked the valves and have them set at .006.
This evening with a replacement plug it was running fine. So, I took it cruising, and decided to drive it until it again quit running right. I drove about 7 miles, and the missing and backfiring started up.
I've hit the wall. I think I've gone as far as I have the capacity to go, and am totally frustrated. I have no idea what to do or try next.
Can a carburetor in any way be causing this?
I'm ready for a new engine, but live in fear that some component I use from this one will cause the same thing, but I can't see how. I have a new distributor, coil, regulator, plug wires, points, and condenser.
Oh, one other observation, and I'm not smart enough to know if this means anything, but when I got home I was poking around the engine, and noticed that the cast intake manifolds were too hot to touch, the middle manifold was warm and the downdraft part of the middle manifold was room temperature.
One suggestion has been a flat cam lobe.
Any and all help will be appreciated.

[David O']

i would change the plugs out, and see if that makes it go away. The only other thing would be a bad plug wire....if you run colored wires, put the real bosch wire on. Can't be a flat lob on the cam, the compression would be off.

[Bill K]

I've changed the plug at least four times. Each time it will run good for about 7 - 8 miles and then foul out from being too rich. I've also tried swaping wires. Nothing seems to solve the problem.

What can cause one bank to run richer than the other when you are using a single carburetor?

[MURZ]

Bill are you sure you have the plug wires in the right spot? On the pass side they are swaped in the dist holes. Should be like this:
3..............1
3 2
4 1
4..............2
Sometimes they get crossed(raise my pledge hand...been there done that)
3..............1
3 1
4 2
4..............2
I know you probably have it right, but just double check it.

[Bill K]

Problem Solved At least I have my fingers crossed that it is.
Turned out to be a real freak kind of thing. Raw gas was seeping into the carburetor throat through the gasket between the top and bottom of the carb. It must have been a warped top or bad casting. Swapped carbs, and so far it's running great.
Sure did cause me a lot of frustration trying figure out what was wrong.