rochester quadrajet carburetor secondaries

[forestb]

I have a rochester quadrajet carburetor on my 350 and am concerned that my secondaries are not opening. I was wondering what the best way is to check if they are.

[crazy longhorn]

Its been a while, but I will take a stab @ it? If the choke does not open all the way, the lockout will not let the seconds open (for cold use). There is an air door on top of the Qjet(seconds), that opens on demand. What I would do to check, would be to take the air cleaner off(not running)....open the choke & the air door, then open the throttle. If you look down the seconds, look to see if they are open. It could be as simple as a throttle cable adjustment, that does not give you full throttle I will turn this back, for the rest of the truck mnuts to post /play longhorn

[MySons68C20]

They're vacuum operated and won't work with the engine off or not under load.

[burnin oil]

Longhorns is right. They are a mechanical secondary setup. The kicker is the air door up top that looks like a choke. That is what keeps them from functioning until demand is needed.

[MySons68C20]

I got the vac doors confused with the actual secondaries....my bad

[geezer#99]

You don’t need to hold the vac door open and stroke the throttle.
Just check the lock out tang on the choke side.
If it’s engaged then no secondaries.
If it stays engaged when completely warmed up then a choke adjustment is needed.

[crazy longhorn]

[QUOTE=geezer#99;8662704]You don’t need to hold the vac door open and stroke the throttle.
Just check the lock out tang on the choke side.
If it’s engaged then no secondaries.
If it stays engaged when completely warmed up then a choke adjustment is needed.[/QUOTE From one geezer to another, I would still check both deals.....how many times have we missed a tenth or 2 on the drag strip, because the adjustment was off on the throttle cable? No argue...shorthorn

[burnin oil]

[/QUOTE From one geezer to another, I would still check both deals.....how many times have we missed a tenth or 2 on the drag strip, because the adjustment was off on the throttle cable? No argue...shorthorn[/QUOTE]

That happened on a buddy's mustang. He swapped a 4 barrel on and reused the 2 barrel throttle cable. His eighth mile was in the minutes when it snapped and he coasted down the track. We spliced it back together for the ride home. Cruise was nice since it now idled at 3500RPM!

[forestb]

Photos of both sides. I checked and I am getting full throttle from the peddle so I don’t think it’s a throttle cable problem.

[forestb]

One more

[ron350]

Forestb can you please post a picture of your carburetor taken from the passenger’s side.

It is difficult to talk about a Quadrajet without pictures.

[forestb]

Will do when I get a chance. Not feeling well right now so it might be a couple of days.

[ron350]

Yes with a warm motor or with a warm electric choke.

[forestb]

So I let it worm up to around 120 degrees, I turned it off and turned the throttle and the little slot didn’t rotate at all and the little lever (in yellow) did not move away from the post on the secondary shaft. I turned it back on and still nothing. I checked the wire that goes to the choke and it has power when the engine is running.

[forestb]

So just to get this straight. I connect a ground to the flat disc and 12 volts to the plug and the pigtail end of the coil should turn counter clockwise?

Just a thought. Because I have an aluminum intake manifold could it be possible that my choke is not getting a good ground?

[ron350]

Yes it should turn counter-clockwise.
You should have 12 volts + to the red wire on the electric choke when the ignition switch is turned to the RUN position.

Aluminum is very conductive your hold down bolts should supply ground for the intake and carb.

[forestb]

Okay thanks

[geezer#99]

Before you pull it apart just compress the choke pull off plunger all the way and see if the lock out tang drops out of the way.

I’ve seen the wrong sealing gasket used on the electric choke when converted from a hot air type. Hot air uses a plastic seal ring. Electric needs a metal one for a good ground.

[forestb]

Originally Posted by geezer#99

Before you pull it apart just compress the choke pull off plunger all the way and see if the lock out tang drops out of the way.

I’ve seen the wrong sealing gasket used on the electric choke when converted from a hot air type. Hot air uses a plastic seal ring. Electric needs a metal one for a good ground.

If it does fall away when I compress it then I need to check the choke? It it doesn’t fall away what does that mean?

[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.