Occasional miss - fouled plug?

[Torakki]

I'm having a problem, (sometimes) with my 70' 2.2 with Webers. I just dropped off some wheels at Harvey's in Oroville and he suggested ask the experts. So, here I am.
Seems, every 3rd time I drive it, it has a miss. First time, I only checked the points and it then ran great again. Second time, checked points and still missed. Took out all plugs (they were dark), cleaned them and it ran great again. It ran great last time I drove it and parked it for about a week. Yesterday, it started up running rough and had the same miss. It feels like one spark plug is missing. Can plugs foul and be cleaned to be good again? I'm thinking to rich on the idle circuit? I don't really rev the engine too much so I'm on the idle circut most of the time. Would turning in the idle screws help? Turning out the air screws? Am I even close? (points, cap, rotor, wires are all new)
Thanks for any suggestions.

[1QuickS]

Check the tips of the idle jets for debris; this is the first stop for small junk in your fuel bowl.

Most efforts to stop debris from entering the fuel bowls revolve around good fuel filters and fresh fuel lines with a tank cleaning. All these are good but there are other sources to check:

• tank filter screen
• vent pipes in top cover of Weber carbs rust internally and drop flakes of rust directly into the fuel bowls
• spark arrester in OEM air cleaner can rust (25mm diameter angled tube at forward end of air cleaner) or the hose connected to it may have crud in it
• the trough where the gaskets for sealing the lower air cleaner housings with the main, top cover can become rusted over time and this rust will be sucked into the vent pipes in the top of the carbs

Assuming a well sealed and cleaned air cleaner and the other issues listed are corrected, there will still be crud entering your fuel bowl; the smallest orifice in the Weber carb is the idle jet. Anything smaller than that will either stay in the bottom of your bowl or be delivered to your engine and spit out the tail pipe. Also, the air cleaner operates with a low pressure so it is natural for atmospheric air to be sucked past poor seals and to bring crud with it.

[Torakki]

Thanks for the response. Great info that one would not normaly think of. The car is very rust free with cleaned and treated fuel tank, new fuel filter and rebuilt carbs. I did check all the jets a few weeks ago and seem pretty clear and clean. "But", yesterday I took the plugs out "again" and looks like the two right hand side, forward plugs where the darkest. I "think" that one float bowl that feeds the two carbs, is flooding those 2 cylinders. I remember those two carbs spitting fuel out the tops on the "first" rev, then once the engine uses up the fuel faster, no more spitting. I'll try a float adjustment today an hope for the best. But also, after I cleaned the plugs again, it ran like a demon. I drove it to the store, ran great but on the way home, it got the miss again. Then it cleared out again. I think at red lights, it floods the 2 cylinders. Anyway, back to the garage...
Thanks!!

[Torakki]

Update: I think I found the problem. Part of it. The float on the front right float bowl was full of fuel and didn't float. I had over compensated, setting the needle inlet valve so it pushed the float open all the time and overflowing the fuel. I found the float had a pinhole in it allowing fuel in. I soildered it up and reinstalled but now I can't get the float level right. It's either overflowing (in the float level gage) or no fuel at all. It's like the float is sticking, but with the top of the carb off, it moves feely. So, adding or subtracting 2 thin shims on the needle valves, shouldn't go from to much to to little? Something is causing this float to be all up or all down. Any ideas? Thanks!

[docrodg]

Fuel pressure?

[1QuickS]

Your float may be upside down.

There is a height relationship of the tab on the float, the main throttle body and the top of the float when everything is correct. Weber has a procedure for checking this. If the float is upside down then the tab will be very angled when it contacts the float needle tip which may cause erratic valve actuation. Pierce manifold has a Weber drawing:

www.piercemanifolds.com/category_s/316.htm

This will get you rather close but the ONLY way to check float levels accurately is with the engine running, using a fuel level vial and with fuel pressure set to 3.5 psi (factory value.) Setting floats statically will not replicate the constant opening/closing of the valve which is a dynamic operation and static setting doesn't work well.

[Torakki]

Update and solution, I think. Thanks again for the responses. Fuel preasure was fine. Just over 3 lbs. (about 3.25) per my gage. Floats are in correctly but that got me looking at them and I noticed that the one that had the pin hole was sitting lower in the bowl, even with more fuel in it. That float had been beat up and repaired (final repair by me) and had lots of soilder on it. So, it appeared heavier. I swapped floats, front to rear and it instantly measured perfect in my fuel level vial. Now the front has the problem but I know how to fix it.
Paul, do you sell individual floats?
I'll try calling you tomorrow.
Thanks again,
Bob

[docrodg]

Nice catch. Just too many repairs over time, all that lead weighed it down. Sounds like one of those causes you wouldn't necessarily think about at first.