Other than the part numbers being different, is there any functional difference between 340 and 440 six pack carbs? I don't mean automatic vs. 4-speed carbs. but rather 340 vs. 440 automatic carbs. or 340 vs.440 4-speed carbs. Just wondering if 340 carbs are okay to use on a 440 and vise versa.

I believe and was taught that the center carbs on the 340 are smaller in CFM than the center carbs on all three years of the 440 motors

hi

340 and 440 outboards are diff .

all 340 outboard are the same .

440 vari jetting by year , manual or auto trans , iron or allum manifold , emission standards .

cab, center carbs are same size; ends same size. calibration and snivies are main difference i don't see any reason why 340 carbs couldn't be used on a 440 with proper re-calibration. difference in air bleeds may be a wild card but i'd think anybody with some carb know how could easily get around that.

The cfm of all the carbs are the same. They are jetted differently. The metering blocks are different in the middle carb, (it’s in the emulsion tube). The end carbs have bigger holes in the throttle plates for the 440(.079) vs a 340(.055). I have not measured the air bleeds yet but they may be different as well. I have never tried to mix between the two cid, but I’m sure it’s possible. If you change the cam much, you can have big or small changes to make to get a proper tune. The last 440 six pack I tune with a wideband O2 meter worked great. I getting my parts all in order start up a six pack restoration service. I bought the remainder of Bill Overcashes carbs, parts and equipment this year. Bill gave me lots of information before he passed but I still having trouble with one color from a new plating company. I’ve done several sets already and they turned out real nice. I just don’t have a very fast source for the Black zinc. I’ve got a set or two I will be putting together to sell. When I do, I list my service on a bigger scale.

hi agin

also 340 carbs have mixture distribution tabs that 440 do not !