I've rebuilt the head on my 36 model 80. All new tune up- points, cap,coil-wires-plugs. Gas tank all boiled out. Great compression across the board. I've had the carb off twice and even sent it out for rebuilding. I can't get rid of what I would describe as a "tail pipe miss" It pulls well with lots of power but will randomly backfire when I let off the gas. I've set the carb float to repair manual specs-it has the Stromberg E22 but when I turn it off it takes about a minute and you hear the gas drip on the exhaust manifold from the carb throttle shaft closest to the motor. It's like the fuel is percolating and I figure if it's doing that when turned off it may be doing it when it's running. I think I may lower the float height. I'm tempted to find another carb but I've got $300.00 in kits and rebuilds in this one. All new needle and seat in carb. I've played with carb adjustments 1/2, 3/4 and 1 and 1 1/2 turn out. Played with sparkplugs and gaps. Number 1 and 8 plugs run tan in color and the others run more of a brown color. All new intake gaskets. I guess I'll run a vacum gauge next-Any ideas or thoughts appreciated. I would even consider a carb upgrade if anyone can suggest one. I don't have any basis to judge against as I have just brought the car out of 25 years storage. I've seen these motors when they are right at shows and they are quiet as a church mouse. Thanks in advance for any ideas

Uneven running sounds like one or more valves may be sticking.

Recheck your tappets & put a little Marvel mystery oil in your gasoline. I use one little airline booze bottle for every ten gallons in my 13 Buick. It helps keep the valves from sticking on their seats.

Couldn't hurt to check to see if the rockers are getting enough oil. You might try oiling the rocker assy and the valve stems too.

Are you able to burn real gasoline, or are you forced to burn deathanol? Less energy in the deathanol, which often causes a miss.

The gas percolating AFTER you shut off the engine, unfortunately, is quite common with modern fuels. It is probably not occuring while the engine is running.

Jon.

Did you think of your ignition timing? I had problems with backfiring when going downhill fast until I found out that my ignition timing was rather late. After advancing it a bit, the problem disappeared.
It also helped a bit against overheating.

Christian