Can't see secondary throttle plates open.

[80BrownK10]

With the engine off and I wedge the back top plate that's vacuume controlled open so I can see what's happening, my secondary butterflies don't open when I push the throttle all the way open. This is with the truck off sitting there not in idle. The linkage is there that connects the primary and secondary is there, the secondary shaft looks like it's rotating. I have a suspicion I have no secondaries. I am new to messing with automotive carbs and want to verify what I am seeing.

I don't think the choke lockout is on in this case but I can verify that tomorrow. I was messing with it earlier and could push it open from the choke side with the lever that hits the choke lockout.

 

[legopnuematic]

Q-Jet? the linkage and arm attached to the drivers side of the carb is spring operated, there is a spring coiled around the arm which allows for the throttle to go wide open with the choke lockout engaged and not bend the linkage to hell. Easiest way to verify is to pull the carb off and from the underside work the secondary throttle blades. some light penetrating oil can help free them up if they are stuck/sticking. The cast metal used for the throttle plate can corrode and tighten up the throttle shaft to where the natural movement of the linkage is not enough to open.

 

[80BrownK10]

Q-Jet? the linkage and arm attached to the drivers side of the carb is spring operated, there is a spring coiled around the arm which allows for the throttle to go wide open with the choke lockout engaged and not bend the linkage to hell. Easiest way to verify is to pull the carb off and from the underside work the secondary throttle blades. some light penetrating oil can help free them up if they are stuck/sticking. The cast metal used for the throttle plate can corrode and tighten up the throttle shaft to where the natural movement of the linkage is not enough to open.

Oh yea, sorry...q jet

 

[75gmck25]

Quadrajet secondaries are vacuum operated, so the engine must be running and have vacuum for them to open. They will never open while idling or if you just blip the throttle.

There is also a secondary lockout in the choke linkage, so the vehicle must be warmed up and the choke off before the secondaries will open. If you push the choke fully open with your finger you should be able to manually open the secondaries.

Bruce

 

[80BrownK10]

Quadrajet secondaries are vacuum operated, so the engine must be running and have vacuum for them to open. They will never open while idling or if you just blip the throttle.

There is also a secondary lockout in the choke linkage, so the vehicle must be warmed up and the choke off before the secondaries will open. If you push the choke fully open with your finger you should be able to manually open the secondaries.

Bruce

The top plate is vacuume operated. The lower butterflies are linked mechanically with the primaries. The way the top works is that with OUT vacuume the top it allowed to open with the air being sucked in. But even running mine can't suck that top plate open if the lower butterflies are closed....as in my case they are. Full throttle no vaccine so it allows the plunger in the little thingy to release it's rod which will allow that top plate your talking about to flop open.

 

[80BrownK10]

Ok there free now. I sprayed PB blaster last night on both side of the outside of the secondary throttle shaft. I also sprayed the insides of the throats on each side where the shaft passes through the carb body. And I sprayed it again this morning before work. When I got home I wedged the choke cutout open and the shaft seemed more free. I sprayed more PB blaster on all spots and then grabbed the linkage and worked it and the butterflies now open with the throttle. Then I worked it several more times while spraying more down the sides of the throats to work into the shafts.

 

[Matt69olds]

Easiest way to verify the secondary side of a Q-Jet is working??? Flip the air cleaner lid. Go out for a full throttle drive, listen for that glorious WOT wail from the carb!!

 

[80BrownK10]

Easiest way to verify the secondary side of a Q-Jet is working??? Flip the air cleaner lid. Go out for a full throttle drive, listen for that glorious WOT wail from the carb!!

Will have to do that at some point. I haven't even driven it since I got them free.

There is a possibility that they have never functioned from day 1 when I bought it.....15 years ago. I was young n dumb...didn't know half what I do now. Never drove a square before that and if they never worked I probably just thought hey it's an old heavy truck. Will be cool if I get power I never had back!!

 

[Catbox]

Opening the secondaries on my big block is fun...

 

[80BrownK10]

OH YEAH there opening now! There is a major difference in the sound as they dump fuel into the intake. Seat of the pants is a little better, but I am running 33s on a truck with the totally wrong gears.