I have 45 DCOEs but I can only help you a LITTLE. Tuning carburetors is one of my many weaknesses.
The first thing I would advise you to do is join the sidedraft_central yahoo email list. There is a lot of very knowledgeable people there. I'll quote liberally from posts from there.
The first thing is to make sure there are no air leaks. The throttle shafts run in ball bearings and they are sealed with leather seals out side the bearings. Here's the advice about determining the quality of your leather seals:
You'll know the leather seals are toast when you fully back off the idle speed screw and the engine does not slow down and die.
If they need to be replaced, dcoe_tuner (the moderator of the yahoo email list) suggests making your own leather seals. Here's a link to how to do it:
https://groups.yahoo.com/neo/groups/sidedraft_central/links/all/Leather_Seals_Replacement_InstructionsI changed mine but I bought new Weber leather seals and soaked them in mink oil and tried to stretch them to little effect but they seem to be sealing. If you do change your seals, you should buy extra sheet metal seal covers as you'll probably tear up your old ones taking them out.
You also need to insure that your float levels are correct. That is best measured with the carbs in the car and measuring the fuel level by pulling out an emulsion tube and putting a piece of paper or card stock in the hole. The process is described on the sidedraft_central.
The next thing that you have to do is warm up your engine. It should be at running temp and ideally, the oil should be at running temp, too. Then balance or synchronize your carbs.
Here are the basic idle mixture adjustment instructions I got at sidedraft_central:
That idle mixture screw is the early twenty degree blunt type. The full dynamic range is reached in about 2-1/2 turns of the threads. So to set the idling mixture correctly the procedure is to slowly close the idle mixture screw until that cylinder lean misfires and then open it up until it runs lumpy and slows down, the proper mixture is halfway between those two boundaries.
I have tried the above instructions but I get confused with the reaction of four carb throats. I started with that and fumbled around with it and read plugs to get to where I am now. It idles fairly smoothly and seems to run good. There is sometimes a slight hesitation from a stop. You should know that reading plugs is not an accurate enough measure of mixture to use for setting idle mixture but if a plug is black and all the others are tan, you can safely lean out the black cylinder. Because I've gotten to where I am largely by trial and error - with a very small amount of knowledge thrown in - I feel there is a bit more that could be done.
You may hear about the "Lean best idle" method. dcoe_tuner doesn't think much of it. I'm not smart enough to have an opinion but dcoe_tuner does some incredible things like make his own jets so I'm happy going with him.
I'm curious about the two different carbs you have. I know there are two different types of idle mixture screws, and there are different number and positions of progression holes over the years. You probably want to make sure that at least your progression holes are the same on both carbs.
I'm clearly no expert at this (to name only one thing) but hopefully I've given you some things to do and think about. If you're interested in books, Passini is supposed to be THE guy. He's written several books on Webers. Haynes has a decent book too.
Good luck and let us know how you do.
