Frank, in response to your message from last week, yes I have checked the timing. At 1,000 rpm the timing using number 6 cylinder should be 10 degrees and I am showing close to 12 degrees advance.
Later this week, I am going to remove the distributor and see if I can figure out why it will not rotate more counterclockwise (retard) than it does. Visually there are no non-distributor engine parts or accessories that would interfere with more counterclockwise rotation. At one time I rotated the pinch bolt bracket more counterclockwise by raising it up over the centering nipple on the block which caused the pinch bolt to be at a slight angle to the distributor shaft body. This gave me more spare retard but resulted in cracking a piece out of the lip on the distributor where the pinch bolt bracket goes around the distributor. I looked at this when I replaced the vacuum retard fixture, but maybe the pinch bolt assembly is distorted in a manner that it limits the counterclockwise rotation of the distributor body. More to come end of week
Front Carburetor Gas Pooling:
All four butterflies are still installed in the carburetor.
I noted the day before yesterday that before I started the car (and with the air cleaner off) that the bottom of the front carburetor piston was wet with gas. I removed the piston and found a small puddle of gas adjacent to the threaded drilling in the carburetor throat located just beyond the block side of the piston into which the carburetor bowl long fastening screw on the block side of the carburetor bowl is installed, which explained why I thought that gas was draining around this bolt ending up on the bottom of the carburetor. The piston was also wet on the bottom and actually all the way up to and on the diaphragm. I wondered if after engine shutdown gas was wicking up the needle and condensing on the piston. I poked a small hole in a piece of white paper towel and inserted it in the carburetor throat and inserted the piston with the needle going through the hole in the paper towel. Over night there was a small very light gas stain around the needle hole and a very light stain about the diameter of the piston. The piston bottom was not touching the piston and the piston was not wet with gas. After replacing the O ring on the needle adjusting fixture yesterday and running the fuel pump (engine off) for about 30 minutes, I had not gas in the carburetor throat nor on the bottom of the piston. However when I drove the car around the block (45 mph highest speed) and returned to the hangar, shortly after engine shutdown I had gas on the bottom of the carburetor bowl that originated from the long center block side bowl fastening screw (the threaded drilling for which is right into the carburetor throat).
Today before even starting the engine I removed the front carburetor piston and it was damp with gas on the bottom of the piston, but not wet. As a side note, oil was still in the air valve guide rod.
I noticed earlier in the week that the temperature controlled vacuum shutoff controlling the air cleaner diversion valve that allows engine exhaust manifold heated air into the air cleaner was not properly working. No matter the temperature of the exhaust air, the diversion valve opened to be the 100% provided air to the air cleaner. I fixed the fixture in the top of the air cleaner between the carburetors so that the fixture would reduce and ultimately eliminate vacuum to the air cleaner diversion valve so that once the engine warms up outside air rather than exhaust manifold heated air would be the primary air source to the air cleaner and consequently to the carburetors. I did not have it quite right for yesterdays around the block run, but made another adjustment last night.
So, today I drove the car about 20 miles including on the expressway at 70 mph. When I got back to the hangar, I did not immediately shut down the engine, but instead removed the carburetor piston cover screws. As soon as I shut down the engine I turned the ignition key back on so the pump would continue to pressurize. I immediately removed the front carburetor piston. There was light layer of gas on the bottom of the piston, but no gas on the side of the piston or the diaphragm. Also no pool of gas although there was a small bubble of gas in the threaded bowl screw hole (screw in the hole).
I put the piston back in its place and set the cover on top. Every 15 minutes (fuel pump still running) I checked for gas on the bottom of the piston. There was a very slight amount the first time, but by the third time, no gas at all. The needle had no gas on it the first time or any of the other times. I let the fuel pump run for 30 minutes and no pool of gas, but a small amount on top of the needle receptacle.
So, could the problem be that the quite warm air to the air cleaner and thus to the carburetor throat and piston at engine shutdown caused the cooler fuel fumes from the bowl into the throat to condense on the bottom of the piston to the point that after a few minutes fuel dripped off the piston and created a pool of fuel in the carburetor throat? Maybe my fixing the air cleaner diversion valve last night reduced this condensation?
I checked the diversion valve just before I got on the expressway and the valve was still allowing only exhaust manifold heated air to the air cleaner. After the expressway run and the 20 minute or so drive back the the hangar from the expressway, the diversion valve was fully closed so outside are was the air source to the carburetors.
I apologize for the long message, but complicated problem.