Jeep Repair: 1983 jeep, fuel delivery systems, jeep cj 5

Question
HI
1983 jeep CJ-5
Inline 6 258 4.2 liter
professionally rebuilt 2500 miles ago.
Weber 2 barrel replaced bbd carb a yr ago

I had in storage over the winter. Last yr went fine, but this year i just cant seem to get it as smooth as i think it should be.

I have adjusted the mixture best i could(best was at 1 1/4 turns out), and using a timing light set the timing to the called for 6 degrees (with vacuum advance disconnected)

I am using good gas, and have been through a few tanks already.

I have sprayed with carb cleaner looking for vacuum leaks, i have ran fuel system cleaner. I have also given it two full tuneups (plugs, wires, cap and rotor).

Also sometimes when am at the engine compartment and i revv the motor, white smoke comes out the exhaust (ring issues already?)

When it idles it has a vibration, more than i think it should, and it bumps every now and then, causing a thud out the exhaust. This is the best i could get it.

I take very good care of the motor, changed oil very often. Ran it often during the winter.

I am stumped as to why this year it does not want to run smooth as it has in the past.

Any suggestions would be greatly appreciated.

thanks

Answer
The only thing that I can think of is that the carburetor may have to be taken apart and rebuilt. Even though you use "Good Gas", it may not be as good as you think. I believe that your state mandates the use of 10% Ethanol blend in the gasoline. That type of gas works fine in fuel injected engines but causes all types of havoc in carburated ones. The reason being that Ethanol is very corrosive and tends to eat away at most metals, that why most modern vehicle now use stainless steel in there fuel delivery systems. The older vehicles don't have that sort of built in protection. So my advise would be to get the carb rebuilt and use a good gas supplement that will counteract the affects of the ethanol blend. StaBil comes to mind, but use the blue marine type not the easily found red type.