General Category > Quadrajet Carb Talk and Tips
Secondary main well air bleed tubes
77cruiser:
--- Quote from: novadude on November 06, 2025, 10:40:28 AM ---I may need to revisit this. I had the four (4) .024" holes in the tube (and maybe a little too high) and it seemed like it was doing wierd things to the fuel curve.
0.027" is pretty small for the well re-fill holes (even in many stock model carbs I've seen). I would guess that the POE fuel probably isn't much of a player after intial WOT?
--- End quote ---
I think all the well holes I've seen were .04.
Kenth:
Only 1974 and earlier Buick units uses the .029" secondary well fill holes.
All Pontiac 1966-74 units uses .034" holes.
Most, if not all other makes/years uses .038"-.039" secondary well fill holes.
And, i have found tuning the Qjet secondaries in a boat, me hanging above the carb, at extended WOT, i noticed fuel pulled out of the secondary "accelerator" ports constantly.
77cruiser:
--- Quote from: Kenth on November 06, 2025, 11:32:20 AM ---Only 1974 and earlier Buick units uses the .029" secondary well fill holes.
All Pontiac 1966-74 units uses .034" holes.
Most, if not all other makes/years uses .038"-.039" secondary well fill holes.
And, i have found tuning the Qjet secondaries in a boat, me hanging above the carb, at extended WOT, i noticed fuel pulled out of the secondary "accelerator" ports constantly.
--- End quote ---
Like this.
http://www.ryanbrownracing.com/video/Qjet_dyno_vid.wmv
novadude:
--- Quote from: Kenth on November 06, 2025, 11:32:20 AM ---Only 1974 and earlier Buick units uses the .029" secondary well fill holes.
All Pontiac 1966-74 units uses .034" holes.
Most, if not all other makes/years uses .038"-.039" secondary well fill holes.
And, i have found tuning the Qjet secondaries in a boat, me hanging above the carb, at extended WOT, i noticed fuel pulled out of the secondary "accelerator" ports constantly.
--- End quote ---
Does that change with small secondary well fill holes? Seems like a really small fill hole would allow the fuel level to drop in the well to where the fuel coming out the discharge would dramatically decrease.
Perhaps a different topic for a different time, but how do the drilled "cobra jet" POE tubes change the situation?
novadude:
--- Quote from: 77cruiser on November 06, 2025, 10:28:39 AM ---I kinda quit testing, I was trying to get serious about by logging AFR & RPM but it seemed to be a PITA with the Innovate stuff it seemed so finicky. I guess since I quit going to the track, & as long as it runs good & can still do a 300 ft. smokey burnout it's all good.
--- End quote ---
I tried datalogging to, but I couldn't get a clean rpm trace with my Daytona Sensors WEGO IV. I gave up before trying a potentiometer or resistor to try and smooth it. Now I just catch glimpses of the meter while trying to keep the car on the road. LOL
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