Author Topic: APT Adjustment Without Choke  (Read 763 times)

Offline Chevynation

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APT Adjustment Without Choke
« on: June 22, 2023, 05:41:38 PM »
Hello, my 7040203 doesn’t have the choke linkage so I can’t perform the tip in procedure as described in Cliff’s book. I also don’t know which way richens or leans the mixture out for my carb. Some people say clockwise leans it out but I’ve heard the opposite on some carbs so I’m not sure. I have the APT screw in the baseplate in the front of the carb. Can I keep leaning the mixture out until the car surges while cruising steady and then richen it up about 1/2 turn like I do for the idle mixture screws? Thanks.

Offline Kenth

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Re: APT Adjustment Without Choke
« Reply #1 on: June 23, 2023, 12:55:53 AM »
Use the palm of your hand to choke the carb slowly.
Look for 150 rpms rise to start with before the engine chokes.
Clockwise APT will lean the mixture on 1975-up M4 Q-jets.
Counterclockwise APT will lean the mixture on 1968-78 4M Q-jets.
7040203 is a 4M unit.

Offline Chevynation

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Re: APT Adjustment Without Choke
« Reply #2 on: June 23, 2023, 09:15:29 AM »
Thank you!