How to adjust Idle 3447S AFB carbs
- Thread starter pruaaron
- Start date
miller
Well-Known Member
Should be doable...all depending on your overall setup...meaning dizzy, cam, so on.
AFB is a AFB. Should I assume a crossram intake? Go to the basics for whatever. You said fresh rebuilt carbs. Assume all is good there!
What type distributor? Anyway, if it was mine...first I'd unhook the linkage at the carbs. You want to check both for freedom of throttle shaft movement, to be sure their clear. Make sure the throttle plates 'can' close completely. Yeah, you've got to back off on the idle adjust screws. Just be sure the plates are lined up right, can close, and all moves free.
If that's good, with throttle plates closed, hook your linkage back up, adjusting so the linkage falls into place, without moving the throttle shaft. Then, pre-set the idle screws, maybe 1/2 - 3/4 of a turn after making contact. That will just 'crack' the throttles, matching both, and giving you a starting point.
Choke plates? If you have some, make sure they are completely open, straight up and down.
Keep in mind about your timing, and idle speed, since both work together...hand over fist. Timing needs to be set while the carbs are running in their idle 'circuit'.
At least you'll know your linkage will allow the throttle to close. Then try it. Depending on all the rest, should have matching idle speed setup (if things are right inside the carbs), and see if you can get the idle RPM you want.
Good luck on it.
AFB is a AFB. Should I assume a crossram intake? Go to the basics for whatever. You said fresh rebuilt carbs. Assume all is good there!
What type distributor? Anyway, if it was mine...first I'd unhook the linkage at the carbs. You want to check both for freedom of throttle shaft movement, to be sure their clear. Make sure the throttle plates 'can' close completely. Yeah, you've got to back off on the idle adjust screws. Just be sure the plates are lined up right, can close, and all moves free.
If that's good, with throttle plates closed, hook your linkage back up, adjusting so the linkage falls into place, without moving the throttle shaft. Then, pre-set the idle screws, maybe 1/2 - 3/4 of a turn after making contact. That will just 'crack' the throttles, matching both, and giving you a starting point.
Choke plates? If you have some, make sure they are completely open, straight up and down.
Keep in mind about your timing, and idle speed, since both work together...hand over fist. Timing needs to be set while the carbs are running in their idle 'circuit'.
At least you'll know your linkage will allow the throttle to close. Then try it. Depending on all the rest, should have matching idle speed setup (if things are right inside the carbs), and see if you can get the idle RPM you want.
Good luck on it.
62MAX
Well-Known Member
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