I have ‘70 Olds qjet on my ‘72 350 that was recently re-bushed for the throttle shafts And the accelerator pump was sticking and that was also fixed. Now the secondary air doors do not seem to open when i get on the gas. The engine bogs and seems to Even flood out. I know where the adjustment screws are so my question is how do I properly set the spring tension At idle so it will perform on the highway? It seems a little better if i plug off the vacuum to the suction diagram but not much. I understand it’s a delicate balance to get them to open at the proper time with the secondary’s. Thanks in advance! Roqetman.

 

Make sure the secondary air door lockout is not engaged after warm-up (pictured). The spring tension is usually 3/4 to 1 turn c/w past door closed tension. The choke pulloff diaphragm actually controls secondary air door opening rate so it must be working properly. You can buy them in different opening rates. Also with engine off have someone floor the gas, make sure secondary base plate throttle blades are vertical, if not linkage may need adjustement.

 

Fron QJet Power (I bought a qjet from them a few months ago ...)

We set them about 3/4 turn from first touch. That is good starting point. Then about 1/8 turn to find the sweet spot +-

 

Thanks! This carb was converted to electric choke pull off... not familiar with the secondary air door lockout. I suppose it is positioned out of the way once the choke has pulled off?

 

Thanks! Mine also has electric choke pull off.

 

There is no such thing as "electric" choke pull-off. There are electrically-heated choke coils. The pull-off is always vacuum-operated.

1. If the choke blade doesn't open far enough, the secondary lock-out may not disengage. The secondaries won't open at all. Some secondary lock-outs are on the secondary throttle shaft, not the air door. Either way, the lockout is controlled by the choke blade position.

2. If the choke pull-off is slow or non-functional, the secondary air door will be slow to open, or won't open at all.

1 and 2 are not the same.

 

Years ago I had a 79 Cadillac that drove me crazy until I figured out it was the air door. That was before the internet (I told you it was a long time ago) and I don't remember how I set it or where I got the info to set it. It did exactly as you described. Good luck on your carb.

 

Consult your CSM.
1. Test the pressure needed with your finger to make the "air door" opens. Check to make sure the tension spring is looped around the pin. Springs have broken or got disconnected.
2. Remove tension to allow the "air door" to open and stay open. Don't just release the pressure instantly, you might have the tension spring become disconnected.
3. Slowly turn the screw C/W til the door closes.
4. Continue turning the tension 1/4 to 1/2 turn and lock the setting with the 3/32" underneath. SCRIBE (scratch) a small reference mark next to the slot in the tension adjustment. Compare the pressure with your finger and make a mental note of it.
5. With the car warm, take a drive and test for a bog. If you have a bog, tighten the tension C/W 1/8 turn at a time and retest.
If you haven't decreased or stopped the bog by the time you have one turn of the tension screw, there may be a problem with something else. Good luck.

 

Schurkey, thanks for the info! I converted the choke on the Qjet to electric and the only vacuum port on the choke housing is now plugged off. Are you saying that should be reconnected? If so, which vacuum source should it be connected to, timed vacuum above the throttle plates or manifold vacuum? The thing is... the carb ran great before I had the throttle shafts re-bushed and as of yesterday it seems the accelerator pump is sticking again.

 

Oldster Ralph, I adjusted the spring tension yesterday, didn’t seem to improve. I did make sure the spring is engaging the pin. Reving the engine in Park to WOT the air doors barely open. On the road it just bogs down completely... which it did not do before I had the throttle shafts re-bushed.

 

You adjusted it to what (1/4, 1/2, 3/4, 1 turn) ?
Did you re-adjust it 1/8 turn at a time ?
If the "air door" is barely opening it shouldn't bog unless the accelerator pump is not doing its job or you have another problem. What happens "on the road" is what counts.
Do the throttle blades open all the way ? Rebushing the throttle shaft shouldn't cause you engine to bog.
On another thread I read, someone discovered they had a check ball missing in the accelerator pump well.

 

The CSM has an excellent section on adjusting the qjet and the air door. The air door can't be checked w no load (i.e. In park)

 

Plus it's a lot more fun to adjust the air door with some WOT runs.

 

don’t forget to flip the air cleaner lid to ensure the Quadrajet WOT howl!