rochester quadrajet carburetor secondaries

[geezer#99]

If it falls away you know the linkage is all good.
If it doesn’t fall away then the choke pull off linkage needs adjusting.

[ron350]

Geezer#99 is talking about pushing the fast idle cam all the way down. (Yellow arrow.)
The fast idle cam has to be all the way down to release the secondary lock out lever. The fast idle cam actually has a knob that manually unlocks the locking lever when the cam is all the way down.

If you already have the electric choke coil removed ( black round disk ) you can open the throttle and the fast idle cam will fall down and unlock the secondaries.

[geezer#99]

Thanks for the awesome pics Ron!

[forestb]

Success. I pushed the fast idle cam all the way in and arm didn’t move so I tightened the adjustment screw in the last photo all the way down so that it would make contact with the top side of the arm that hangs down when but it still didn’t make enough contact to move the arm. So I removed the arm that the adjustment screw is attached to and bent it a little so that it will fully engage. I also did a tiny bit of filing on the end of the rod that goes through the secondary rod. Just for extra clearance. Now then I push down on the fast idle cam and tun the throttle the secondary rod rotates 90 degrees.

If all of that doesn’t make any sense just know I got it to work thanks to all of you all’s help. I now feel like I can safely get up to speed on the freeway.

[geezer#99]

That screw you adjusted is used to control how far the choke is opened when you first start the motor cold.
You might need to make an adjustment.

[ron350]

Sorry for the misunderstanding with the crummy yellow arrow.
The part with the screw is called the Vacuum Break Assembly and is supposed to pull the choke open a little when the truck is started. On your Q-jet the Vacuum Break just about covers up the Fast Idle Cam that is why I suggested removing the Electric Choke Coil.

The Fast Idle Cam is the part that is just under the Vacuum Break and is difficult to move on your Q-jet.
The picture below shows the Fast Idle Cam on a different model Q-jet.

[forestb]

So what is the little arm that the adjustment screw goes into after it goes through the spring supposed to do?

The part that you are holding up in the photo swings around pretty freely.

[forestb]

So then I am supposed to push down/forward on the fast idle cam and see if it moves the arm that is hanging down out of the way of the rod that is going through the secondary rod of. If my memory serves me correctly it moved it out of the way when I did that today. So what should I do if that works.

[ron350]

The screw on that Vacuum Brake arm adjusts how far the choke opens. If you look closely you will be able to see where that vacuum brake arm (with the screw) contacts part of the fast idle cam.

[forestb]

I will have to take another look. But I think that is what I had to adjust it so far to make contact with but I might be wrong are you pointing at the slightly green post below the popsicle stick or the one directly to the left of the popsicle stick stick?

[forestb]

Originally Posted by ron350

Sorry for the misunderstanding with the crummy yellow arrow.
The part with the screw is called the Vacuum Break Assembly and is supposed to pull the choke open a little when the truck is started. On your Q-jet the Vacuum Break just about covers up the Fast Idle Cam that is why I suggested removing the Electric Choke Coil.

The Fast Idle Cam is the part that is just under the Vacuum Break and is difficult to move on your Q-jet.
The picture below shows the Fast Idle Cam on a different model Q-jet.

When I move by hand the Fast Idle Cam clockwise the rod that hangs down moves away so that the secondaries are free to move. But when it is wormed up the arm that hangs down does not move out of the way.

[ron350]

Yes the green lever.
You have to understand that your carb is going to be slightly different form the one I have.

You realy should buy a Quadrajet rebuild book. Those books explain things so much better than i ever could.

[geezer#99]

Originally Posted by forestb

When I move by hand the Fast Idle Cam clockwise the rod that hangs down moves away so that the secondaries are free to move. But when it is wormed up the arm that hangs down does not move out of the way.

That means your choke is set too rich.
Loosen the screws on the black cap and rotate it all the way leaner. Then check the arm for dropping away.
Hold the throttle open slightly to do that.
Let us know what that does.

[forestb]

Originally Posted by geezer#99

That means your choke is set too rich.
Loosen the screws on the black cap and rotate it all the way leaner. Then check the arm for dropping away.
Hold the throttle open slightly to do that.
Let us know what that does.

which direction do I turn it to make it lean?

[geezer#99]

Honestly my memory doesn’t work for that.
I think it’s cw leaner.
You can figure it out easily.

Loosen the screws, crack open the throttle and turn the cap.
Go clockwise first. Watch the choke blade. If it opens then that’s leaner. If it stays closed that’s richer.
When the choke blade opens completely the fast idle cam should drop right down.

[forestb]

should I do this with the engine hot and running?

[geezer#99]

No.
Do it cold and not running.

[forestb]

Remind me which one is the choke blade?

[forestb]

So I readjusted the little bracket back to where it was using the screw and then I loosened the screws on choke and rotated it clockwise until the choke blade opened all the way up and the fast idle cam dropped forward and the arm dropped away. I have not gotten a chance to see if it will do the trick. I am still confused about what the bracket at the end of the adjustment screw does. I forgot to crack open the throttle a little when I did this. Will that make a difference?

[geezer#99]

That bracket with the screw is supposed to adjust how far the choke blade is opened by the choke pull off pot.
When you start your motor your choke blade should be closed before it fires up. The choke coil does that. Upon firing vacuum is supplied to the vac pot and the choke blade opens just enough to let it idle well.
You want the choke open at the sweet spot. Just enough to idle cleanly. Not too rich(closed more) or too lean(open more).
Choke blade should be about 1/4 inch open.
Adjust with the screw.

[forestb]

So adjusted the choke so that the door is almost shut. It opens to about 1/4 in when I first fire it up. After it gets worm the choke opens but it seems like it doesn’t quite open all the way. The little arm that locks up the secondaries moves out of the way but I think it could move a little more but I don’t know how much that matters. I can still move the fast idle came Clockwise a little. When I do the doors open all the way and the little lock out arm moves forward more.

[rpmerf]

http://www.capitalcorvetteclub.ca/at...ng%20Paper.pdf

Lots of good technical info on the QJet. Technical Procedure 3 is setting up the choke.

[forestb]

Thanks I will take a look

[forestb]

So for the third time I think I’ve got this figured out. The timing seems to be adjusted correctly the flap opens all the way up and the little bar that hangs down is moving out of the way properly. I realized that the air flaps for the secondaries were sticking a little bit open and not closing back up sometimes so I slightly tight in the spring on those so they close every time. Everything seems to be working right now and my secondarys seem to be working fine. I am also not getting the stuttering problem that I was having before when I pushed on the throttle. Thank you all for your help.