Q-jet
10-14-2005, 06:19 PM
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Q-jet well i got another carb. i have run a holley but swaped a Q-jet in. my problem is i really dont think the secondaires are opening. the car runs like a pig and wont rev past 4k under a load. with the holley it runs fine... since its nearing the end of the racing season i have been tinkering around. I think once is all said and done the holley is going back on. Just wondering if there is something simple i can checkwith the Q jet
Last edited by 3rdgenguy; 10-14-2005 at 07:01 PM.
10-15-2005, 07:50 AM
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There is a gizmo off the choke / fast idle linkage
that keeps the secondary air flaps from opening when
cold. Other than that, the flaps just move by vacuum
and you can set spring tension (a little screw on the
flap "axle" and a set-screw that is only seen from
underneath).
Good luck with it... I've "rebuilt" a couple or three
Q-Jets and every time they end up worse than when
I started. At least the Holleys I can get close to
right, they're meant for hobbyists to mess with.
that keeps the secondary air flaps from opening when
cold. Other than that, the flaps just move by vacuum
and you can set spring tension (a little screw on the
flap "axle" and a set-screw that is only seen from
underneath).
Good luck with it... I've "rebuilt" a couple or three
Q-Jets and every time they end up worse than when
I started. At least the Holleys I can get close to
right, they're meant for hobbyists to mess with.
10-15-2005, 12:22 PM
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the secondaire air flap isnt comeing open i unplug the vacume source and watch the rod move. it moves all the way over but doesnt seem to be opening the air flap or moveing the secondarey metering rods. is it possible that the main throttle plates are opening but the air flap and metering rods are not moveing? or maybe since the diaphram is 30 something years old doesnt have enough pressure to open the air flaps once the vacume isnt applied to the diaphram or, something to that effect
10-17-2005, 06:19 PM
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take a legnth of tube & see about sucking that thing open, or use a vacuum gun/one man brake bleeder & measure the vacuum needed.
ANy chance on procuring a mechanicall secondary quad if all else fails?
ANy chance on procuring a mechanicall secondary quad if all else fails?
10-19-2005, 05:26 PM
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got the problem figured out.. okay i took the carb off the intake then went to the toolbox for my special secondary adjusting tool.. i then smashed it to tiny pieces with the special tool aka my hammer......then put the holley Hp back on. problem solved 
10-21-2005, 06:40 AM
#7
Wow. And secondaries on a Q-jet are easy to adjust. You undo the set screw (torx on later Q-jets), adjust the (flat tip) secondary spring enough to keep them closed at low rpm use, retighten the set screw and fine tune from there. The air door up top is opened by vaccuum; the diaphragm isn't for their opening; it's to keep them closed when under choke conditions.
Mechanical secondaries are an aftermarket / DIY thing only for the Q-jet.
Mechanical secondaries are an aftermarket / DIY thing only for the Q-jet.
