Repairing the Thermo-Quad on my 360. It's a 9811S that I bought used, rebuilt and tweaked it about 25 years ago. The car ran well, but was moderately hard to start after running, then sitting a short time. When it fired, it belched black smoked. I suspected a drain back due to the quad X-rings or the bowl jet wells. This only started recently. I also noted that the accelerator pump was not squirting, but you could not tell when driving it. That was just a stuck check valve below the pump cluster (squirter).
Because it is in decent shape, like all my carburetors that I have previously done, I only repair and replace what is needed unless the condition warrants a full rebuild. I tore it down and found the quad X-rings had deteriorated. I switched everything to non-ethanol gas in 2014-2015, but this had run time before that. The body gaskets were reasonable, but brittle enough to break when separating.
The jet wells looked okay, but I set up a test of the jet wells with gas and lacquer thinner in the bowls, with the outer surfaces clean and dry sitting on a paper towel and watch for any leaking over a few hours. There was no leakage.
Because it is not a rebuild, I did not use my old, good, Berryman carburetor cleaner boosted with MEK, but cleaned the parts with spray cleaner. For repairs, I don't use a kit, just pull parts such as gaskets from my collection.
The original nitrophyl floats were good, and I have a few new floats from which to choose, but I opted to switch to brass.
After repairs, it was reinstalled and works fine again.
The deteriorated X-rings were allowing the gas to drain into the engine resulting in a flooded condition that caused the hot start issue and subsequent black smoke.
The 9811S Super-Quad here was originally equipped with an electric choke. It was missing from this one, but I am using it on a stock 340 intake with the factory divorced, electrically assisted choke on this engine.
Great way to make smoke for testing but the smell is horrible
