Happy Days! I have found the issue with the pump jet in the two carbs. There is no passage into the air horn casting like in the other carb. There is a very small jet machined into the top of the well with the little metal "T". It was plugged despite a week of soaking in a can of carb cleaner. After clearing to blockage with a wire and putting a 55 jet in it is running like a top.
I notice that the jet and the corresponding squirt is much smaller on the models without the jet in the air horn casting. It still runs great with no bog on acceleration.
For setting the idle mixture I used a vacuum gauge on the manifold and set it for max vacuum. I notice there is a fairly large range where the vacuum is steady at max (it stays around 15.5 for around 3/4 turn of the mixture screw). Should I shoot for the rich end, the lean end or right in the middle of max vacuum?
Also, I am having an issue where after running the engine for a while and then shutting it off it seems like pressure is building in the fuel line (probably from the heat) and this is causing fuel to push through the float valve and overflow the bowl a little. Not a major issue for drivability, but it leaves a gas smell behind. Does anyone know of a way to prevent this issue? I was thinking about insulating the fuel line or putting a tee fitting in the line with a pressure regulator returning to the input line to the fuel pump to allow the pressurized fuel to vent back to the tank over a certain pressure (like 8 psi).
Thank you so much to everyone for the help.
