Setting Q-jet vacuum pull off?

[Longroof79]

Just a simple question regarding the adjustment of a Q-jet choke pull off. The choke pull off works fine, but opens a little too wide and the engine stalls. I believe the choke butterfly should open to approx. 1/8". Which way does the adjustment screw turn in order to narrow the opening? I realize it has to be done gradually, and in a few steps.
Someone please enlighten me. I guess I could also use the Mity-Vac to activate the pull off while it's cold, and make the necessary adjustment.

 

[Bonnewagon]

Jack use the Mity vac. Adjust while watching it move. Rule is- stalls out is too lean, stumbles is too rich. Let me look up what an old Chevy was set at.

 

[Bonnewagon]

Jack the last year I have specs for is 1973. All '73 Chevy 4 barrel engines used .250" as the vacuum break setting. I use drill bits to measure with. I know it's hard to test when the choke heats up fast but using the Mity Vac helps a lot.

 

[Longroof79]

Thank you, Mark.
I knew if anyone would know, it would certainly be you. I think I read something to the effect about using an 1/8" drill bit. Which way would I turn the adjustment screw to richen it up? Looking at the mechanism itself, it's difficult to determine.

 

[Bonnewagon]

Jack sorry- Microsucks decided to force an upgrade upon me uninvited. Took a friggin' half hour. Anyway- it is a regular thread screw so righty-tighty, lefty-loosy. Turning clockwise would pull the tab towards the screw head and vice-vesra. So counter-clockwise will increase the flap opening and clockwise will close the opening. The usual range is 1/8" to 1/4" but every situation is unique.

 

[Longroof79]

Thank you, Mark,
Much appreciated, my friend. Say, by applying vacuum to the break canister, can I actually see the flap move as I turn the screw clockwise? I was trying to adjust it daily, while the engine was cold, but did not see a significant change. I would try turning it a full rotation at a time.

 

[Bonnewagon]

Yes Jack. Open the throttle so the choke closes. Apply vacuum to the pull-off. It will open. Then adjust. You can see it move. Sometimes if it is cranky I adjust it then let it close and open it again. Adjust each time and repeat until it is where you want. Don't "eyeball" it- use drill bits to measure and record how it ran upon start-up. I often have to re-adjust for the seasons. Winter can require a richer setting than summer. It was OK to leave it rich all the time with older motors but if you have the carb adjusted for economy then the weather can affect it. TIP: if you adjust your choke housing overly tight- then it will take longer to open the choke flap, giving you more time to test each adjustment.

 

[olds307 and 403]

Clockwise closes it I believe, screw threads into the contact and pulls the contact further away, it always seems backwards to me. If you are running an open air cleaner, or even my dual snorkel with no heat risers hooked up require a richer setting.

 

[Longroof79]

Thank you guys. I appreciate your tips, help, and information.

 

[pontiacgp]

I'm lazy, I use my A/F gauge to set the pull off, I set the opening so I have 10.5 - 11 on the gauge.