52 twin H idling rough

What filters, the strainer screens in the carbs? I bet there's trash in the carbs. Those screens basically only stop big flakes and pebbles. Something is probably plugging up the idle port. Either way its not running how it should and both carbs deserve and good rebuild and full adjustment job from top to bottom.

My car came with 2 additional carbs in a box that were "rebuilt" and never installed. They looked like they were in better condition than the ones on the car. I put them on the car and it started ran and drove mostly functionally but nothing was right. I ordered 2 rebuld kits and downloaded the old Carter manuals. With the Hudson Service manual and the Carter manual I was well prepared to bring these back to their intended glory.

It turns out...nothing in my carbs was properly adjusted to Carters specs. There were issues of every variety.

Most of the time carbs get "rebuilt" by simply spraying them out with a can of spray and carelessly installing the kit. It's best to understand exactly how it works and WHAT happens and WHY at all stages of the process for a carb to provide reliability and ensure that it's not overfuelling or underfuelling these flatheads.

These Carters are simple but excellent. They are a great way to learn and understand how all carburetors in general work.

I made adjustment tools from old screwdrivers with a with an L shaped notch cut in the end with a dremel cutoff wheel for bending the arms on the float, the metering rod, the idle choke unloader arms , etc.

Take time to confirm the throttle plates open and close to the exact spot they're supposed to and that they dont get bound up at all or they can close off the idle hole or change the flow rate of vacuum. Make sure that they both open freely and equally as the choke releases them. Use a fine wire from a bread twst tie to poke thru the small passages. Do what the manual says and adjust the choke unloader and idle cam while off the car. Make sure the springs inside the carbs are of equal strength. Add a Wix 33033 filter somewhere between the tank and carbs to stop trash from getting in. Add Lucas, Marvel , or synthetic marine 2 stroke to the gas at a ratio of 640:1 (thats 4 oz of oii in 20 gallons of gas). With engine running spray around the bases of carbs with starting spray to make sure no vacuum leaks are letting unmetered air sneak in to interfere with your plan, lol.

All these things will help to optimize the system and these Carters won't let you down.