Secondary' s wont kick in

[Fred C.]

I have a 69 with a stock rochester carb. The car runs great and everything on the carb appears ok but the secondary's are not kicking in. What should I check?

thanks for your help
fc

[Kenneth T.]

Re: Secondary' s wont kick in

I have a 69 with a stock rochester carb. The car runs great and everything on the carb appears ok but the secondary's are not kicking in. What should I check?

thanks for your help
fc

Fred, I could be caused by the choke. Check the passinger side of the carb. When the choke closes it pull up a cam that locks out the secondaries, sometimes when the butterfly opens, the cam sticks and remains in the locked position. If you still have a problem, I will send a photo of it engaged and off.

KEN

[Duke W.]

Re: Secondary' s wont kick in

Are you sure? The Q-jet secondaries are of the "constant vacuum" type - like the old English SU. The "air valve" at the top of the secondaries will not open by manually pulling the throttle to the stop and will barely begin to open if you blip the throttle hard at idle.

With the engine off, but warm and choke full open, manually open the air valve. Then have someone in the car push the throttle pedal all the way and look to see if the secondary throttle valves at the base of the carb open up all the way.

If they do, there is likely no problem. If not, the throttle linkage/cable or secondary opening/lockout linkage on the carb should be adusted IAW the applicable CSM.

Duke

[Jim T.]

Re: Secondary' s wont kick in

The secondarys have actually stuck closed on my Holley because of the butterfly valves sticking to the bore of the body. Some gentle persuasion fixed the problem. More use of the secondarys has prevented it from reoccuring.

[Kenneth T.]

Re: Secondary' s wont kick in

Perhaps I am shooting from the lip too soon, I have posted pictures to explain what I almost said The first two show the choke closed with the cam locking the pin on the secondaries. The third shows the butterfly held open and the cam drops away. The engine is not running, so no vacuum.

Ken

[Fred C.]

Re: Secondary' s wont kick in

Ken thanks for the help. I will check it out this weekend---------
many thanks
Fred

[Kenneth T.]

Re: Secondary' s wont kick in

Ken thanks for the help. I will check it out this weekend---------
many thanks
Fred

Fred, I first thought of a mechanical bind only. Duke's post is correct in that the carb secondaries function are subject to maniford vacuum and atmospheric pressure once that stop is released. If you do not have a mechanical bind, you can check this link for Q-jet functions and help. All pdf format you can download or just view. Good luck.

http://www.tocmp.com/manuals/Carbs/Rochester/QJet/index.htm

[Clem Z.]

Re: Secondary' s wont kick in

i have seen where bubba had tighten the 2 back screws so much it distrorted the top enough that the air valve was jammed tight and would not open

[Kenny C.]

Re: Secondary' s wont kick in

OK on a side question, in examining the photo's I see TWO vacuum tube retaining clips. Is this correct or is there supposed to be just one?

[Kenneth T.]

Re: Secondary' s wont kick in

OK on a side question, in examining the photo's I see TWO vacuum tube retaining clips. Is this correct or is there supposed to be just one?

Good eye Kenny. I had disconnected the CEC system many years ago and have been slowly been putting it all back to original. I reconnected the soleniod on the carb and put back the metal and hose vacuum line with the clips on the manifold, but I still have the advance running straight from the carb.
The wire to the transmission switch touched my engine pipe and burned through and so until I fix it the wire, the system will not work as designed. So, just one is correct.

Ken