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72SB · 02-22-2024, 05:28 PM

Have a 1406 and have used them on a few SBC & Ford motors. They basically are a Carter AFB.

You can download the 1406 "owners manual" which comes with the carb. Very detailed on adjustments

OP, put your vacuum advance on the other port (DS) on front of carb. That is manifold vacuum. You currently have it hooked up to timed, aka ported, vacuum, never do that.

You need to confirm your timing is good before making carb adjustments. You want 20-24 degrees advance WITH VA connected at idle. Generally 10-12 degrees base WITHOUT VACUUM ADVANCE, then with VA connected it should add another 10-12 degrees for a total of 20-24 degrees at idle. Without VA connected at 3k RPM you should have 35 degrees of timing.

Set idle after motor is completely warmed up and confirm choke if fully open. "Maybe" your idle was set before choke fully opens and when it does, its to low.

Appears you have been running rich so get the carb cleaned up with some carb cleaner. A Vacuum gauge is very helpful in tuning a carb. Vacuum leaks will mess up everything so fix those if you have them.

Generally the mixture screws on front of carb are set about 1 1/2 turns open. Both need to be same. In fine tuning you may need to open or close them about 1/8-1/4 turn to get it right. Then set idle RPM. 650 if manual, 750 if auto (in neutral). Cam motors typically need a little more RPM at idle. Sometimes 825-850 ROM.

Edelbrock makes a tune kit specific to 1406 but really not needed for stock motors. Camed motors making power than you need that kit.

02-22-2024, 05:28 PM	#11
72SB Registered User Join Date: Apr 2022 Location: Moorpark, CA Posts: 702	Re: Carb Adjustment Question Have a 1406 and have used them on a few SBC & Ford motors. They basically are a Carter AFB. You can download the 1406 "owners manual" which comes with the carb. Very detailed on adjustments OP, put your vacuum advance on the other port (DS) on front of carb. That is manifold vacuum. You currently have it hooked up to timed, aka ported, vacuum, never do that. You need to confirm your timing is good before making carb adjustments. You want 20-24 degrees advance WITH VA connected at idle. Generally 10-12 degrees base WITHOUT VACUUM ADVANCE, then with VA connected it should add another 10-12 degrees for a total of 20-24 degrees at idle. Without VA connected at 3k RPM you should have 35 degrees of timing. Set idle after motor is completely warmed up and confirm choke if fully open. "Maybe" your idle was set before choke fully opens and when it does, its to low. Appears you have been running rich so get the carb cleaned up with some carb cleaner. A Vacuum gauge is very helpful in tuning a carb. Vacuum leaks will mess up everything so fix those if you have them. Generally the mixture screws on front of carb are set about 1 1/2 turns open. Both need to be same. In fine tuning you may need to open or close them about 1/8-1/4 turn to get it right. Then set idle RPM. 650 if manual, 750 if auto (in neutral). Cam motors typically need a little more RPM at idle. Sometimes 825-850 ROM. Edelbrock makes a tune kit specific to 1406 but really not needed for stock motors. Camed motors making power than you need that kit.