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Rochester q-jet carb problem?
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Guest
Anonymous Poster
jetdoc3037@hughes.net
May 2, 2007, 4:05 PM
Post #1 of 3
(3710 views)
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Rochester q-jet carb problem?
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Hey all...here is my problem, caused by me.
I have a Rochester Q-jet carb. Its on a 76 Corvette. Well I thought the fast idle was too high so I went to lower it. Turns out I was turning the choke pull off screw, not the fast idle screw.
I went out this morning to start it and it just turns over. The butterfly is closing all the way, then when I turn the key its opening about 1/4 inch, and I can smell fuel.
I do not know where to adjust the choke pull off screw for a good starting point, let alone back to where it was before I started to mess with it. I've tried all the way in, all the way out, in the middle and no start still. It keeps turning over, thats it.
I had ZERO problems before I screwed around with the carb...what a d/a I am, lol. No problems other than the perceived high fast idle, which was about 1300 rpms when cold, then to 700 when warm. I've been told that 1300 for a fast idle isn't too bad actually and it did kick down as it was supposed to.
Thanks in advance.
RonW
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
May 2, 2007, 5:44 PM
Post #2 of 3
(3708 views)
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Re: Rochester q-jet carb problem?
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When cold get the choke to set by just touching the throttle. Choke should be fully closed. If you have a hand held vacuum pump apply vacuum to the pull off diaphragm. Use drill bits to measure the gap at the top between the choke butterfly and the air horn wall. The exact # it should be can be found and I may have it but it will refer to the carb # which is like 17051432 but will be like that starting with 17. That's on the side of the carb towards the back on driver's side.
Gap it probably too little right now and since you have no other info at this time put it to about a 1/8 drill bit size. I can find the exact # if you get the carb #.
Make sure you are dealing with the primary choke pull off and not the one towards the rear of the car.
If you don't have a vacuum pump you can just push in the bar into the diaphragm by hand but that's not as accurate. When you get close try it cold and see how it does. You only have one shot at this a day really. Must be cold. If it seems lean just by eye adjust 1/2 turn to richen at a time and keep count from you starting point.
When that's all set you can adjust the speed on top of the choke camstep to about 1,800 RPM and it should kick down to next step with the throttle pushed.
Whatever you try ---- don't drop drill bits down the carb!!,
T
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