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Discussion Starter #1
Need a few ideas here....

The on the Cat is the newly rebuilt Carter AFB (9637), 625 CFM, on an A-code. I can't for the life of me adjust it to the spec 525 curb idle speed without making the mixture so lean that the car barely runs. If I make things just rich enough where it doesn't sound like it's about to die, I can't get things below about 625 even backing out the air speed screw all the way.

Would the larger carb (a stock Autolite 4300 is 480 CFM) affect the ideal idle speed? If so, what should I be aiming for? What else should I check?
 

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I'd shoot for a 700 rpm idle in gear (auto) or out of gear (manual)...

First, get the idle speed as close to that level as possible, then check timing and adjust to 8-10 BTDC; note idle speed and adjust as necessary. Once this is complete, adjust carb mixture to about 2 turns out on each screw; note idle speed and quality. Turn each screw in until stumbling is noted, then back to where smoothest operation is noted. Re-adjust speed to benchmark with idle speed screw (you should always adust speed with the throttle plates, not the mixture screws).
After carb mixture and speed are optimized, do one last timing check (it should be close) and do any final adjustments to timing and idle speed. Then run engine up to 3K and note operation and timing (should be 32-36 BTDC). Lastly, test drive and check for detonation (under WOT) and in-use curb idle. Adjust as necessary.

Have fun!
 

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Discussion Starter #3
Thanks, Pat, I'll try it out.

Might I ask why you suggest 8-10 BTDC? Shop manual says 0 TDC for non-thermactor and 6 BTDC with Thermactor. Mine originally had the Thermactor, but it appears long gone, so I had things set at 0 TDC.
 

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Discussion Starter #4
(you should always adust speed with the throttle plates, not the mixture screws).
Right, I made a very poor choice of words. Having been unable to set the speed low enough using just the air speed screw, I was thinking I could adjust things using the mixture screws.
 

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I believe the service manual timing setting had to do with emissions (getting the then-new technology to meet standards) more so than with performance. Retarded timing like that IME would cause rough idling. The resto gurus who are still running the OEM smog equipment might have better advice than I; smog stuff was always the first thing I threw in the trash, much to my financial detriment now *G*
 
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