The B.S. never ends with this project. After a successful cam break-in (finally), this thing is idling rich. Turning the mixture screws does NOTHING. I bought this carb from Summitt 10 or 12 years ago and never took it out of the box until I was ready to use it. Right out of the box, the needle/seat, and float hanger were bad which caused it to dump fuel. Had a friend fix that for me and life was good.........or so I thought. There is no change on the vacuum gauge or idle quality even with the screws turned all the way in. Initial timing is around 12°- 13°. Choke is wide open. What causes that?...

 

What idle rpm are you at? If the throttle plates are open past the transition slots, then the idle mixture screws will not have any effect.

 

If it is a stock rebuild or mass rebuild, all bets are off. Too many parts that do not match being slapped together and runs like garbage is the result. Hopefully Summit used a better supplier, but I honestly have no idea who setup their carbs.

I have built and recalibrated alot of these carbs and they work quite well if you can find a decent core with all matching parts.

 

Idle RPM is around 800.
Yeah, this carb is junk. the model number on the throttle body was ground off, and the base is from a different year than the airhorn. I really got screwed when I bought it...