Spent a little time on the camaro's Carb yesterday. The Rochester has never really run run right. When you went to start the car it would smoke very badly and the High Idle was set to high. A little investigation yesterday found the fitting that came out of the carb that fed the chaoke pull of had worked loose. I reinstalled it and put the choke pull off under a vacuum with my tester. The pull off was functioning but the lever was way out of adjustment. The screw I'm talking about is not the high idle underneath but the choke break screw on top located above the choke housing assy. ONe I got it to open the choke plate correctly I started her up and no more smoke, to lean when cold. The high idle was around 2500 rpm and was adjusted down to 1600.

I did have to repair the hot air circuit as both of the steel tubes had worked loose and would not allow vacuum to draw hot air . I also verified that the secondaries where free and functioning. If you have ever wondered how these carbs work and function take a look at Youtube.
This link is to "Everything you wanted to know about Electric chokes", he also has one on how to get rid of the bog on your secondaries, take a look they will help you understand the rochester.
YouTube - ‪Everything you wanted to know about automatic chokes but were afraid to ask‬‏

 

My only problem is that you can't tune out wore throttle shafts, warped bodies, and the 24 other things that are inherent to Q Jets.

 

They are very simple to rebuild. From what I've learned about these babies, they are very fickle about vacuum. The more vacuum you can pull outta one the better it performs.

 

I like Q jets when they are in good shape. I've had a few that were very strong runners. We used to peruse the junkyards looking for big GM V8 cars to grab the Q jets off and use them on our smallblock Chev engines. The big V8's had large Q jets and they were cheap in the old days, and a real performance increase to poor hotrodders that wanted cheap performance mods like we did.

 

The variable venturi secondaries are awesome. It will only flow what the motor is asking for, the transition on mine is perfect and the power very smooth up to 6200. I don't like to pull much past that.

 

You can get throttle shaft bushings from Cliffs performance.

 

I have no problem with there performance. When the secondaries pop open they cave the hood in. Its just hard to tune one that is pulling more vacuum through the shafts than the blades.

 

I think I saw that site before. They sell a fixture to straighten the warped bodies, for like $400. They actually call out 26 defects that come with all QJets. I have no problem with there performance. When the secondaries pop open they cave the hood in. Its just hard to tune one that is pulling more vacuum through the shafts than the blades. I read up on them before rebuilding the one on the TA I had recently. It laid stripes for as long as I wanted, but the idle was all over the place with the shafts loose. I had a spare Holley so I used it.

 

The kit includes a drill bit with guide to bore out the shaft bodies then install the bushings and shes like new. My sons carb looks ok for now, but may be later. I have a 330 Olds with an early rochester that could use some bushing work.

 

The Q jets really do flow when those secondaries open! Had a big one on the 283 in my '67 Chevelle and it had a sound all it's own when those secondaries opened up! Passengers would look over at me when I punched it and ask, "What the heck is that?"
It was pretty funny!