Ok, Once again .....here I am

I have a QJ that I am not happy with the the transition from primary to secondary
I Bent the rod (red) towards the lever (blue) as Doug Roes book suggests to 0.50"

The secondaries now open the way I expected but now the idle sucks and is running rich
I adjusted the curb idle to max Vacuum but it is still very rich....
Any help will be much appreciated

ps: this is not the carb I am working on, just a good example of the linkage.

Thanks
Still learnin

 

Put it back the way it was. The secondary "air valves", the two big butterflies on top of the carb is what you need to adjust.

On the passenger's side of the air valve shaft, there's an adjustment screw held in place by an allen head set-screw (3/32" allen head wrench I think). This adjustment will determine how soon or late your secondaries open when you "go loud".

I don't think the Roe book discusses this adjustment,..but it's important.

Only adjust the screw a 1/8 turn at a time, and don't let go of the screw with your small screwdriver until you've re-tightened the set screw. The adjustment screw is spring-loaded and will unwind if you let it go and it's difficult to fix.

If you make the adjustment and you get the "q-jet bog", turn the screw clockwise until the bog goes away (again in 1/8 turn increments). If the secondaries are late, turn the screw CCW.

Good luck!

 

Thanks... After reading through Doug Roe does discuss the method you explained
It seem you have to be VERY careful while adjusting the Air Valves........ thanks

ps: how did this secondary adjustment I made (bending the rod) make such a huge difference in the primary circuit?

 

If you adjust this rod incorrectly it can hold the primaries open.

BigBlockk

Later.....

 

I knew that

Thanks BB

 

It's hard to find the Allen screw, see it in the mirrow in my picture.
The piece of tape is holding the Allen Wrench while I take this picture.
The black handle screwdriver is on the adjusting screw. Follow the
instructions above, drive it, and maybe adjust again.

 

Thanks Lucky
I am aware of this adjustment, I was reading Doug Roes Book and thought I would give the bending a go as it was out of spec.
I will set it back as close as I can and then play with the air valve adjustment as you have posted
Its just been too damn hot up here lately and I'm still battling my third time around with Lymes Disease so everything is a major chore

 

The Doug Roe book has another way to improve the smoothness of secondaries opening.

When you pull the top bowl cover assembly off there are four 'tubes' about an inch long near the centre of the cover that hang down into the carb. On two of these tubes you can drill 4 small holes. Apparently Ford Cobras had this mod done to them stock. You definetely want to reference Doug Roe's book to see what I am talking about.

FYI here is a whole wack of carb links:

http://www.buickpartsdirectory.com/carbs.htm

 

Bending that area of the linkage can result in the secondary throttles being slightly cracked open at idle. If this happens, there will be a low pressure area created between the secondary throttle plates and the secondary airvalve, and this will pull fuel out of the secondary discharge tubes at idle, giving you the rich condition.

 

Thanks Lars
I bent the rod back to the same location it was at and it is still running super rich????

 

Thanks Boofers
I have bookmarked the sites
Lots of stuff there

 

the secondary throttle valves must seal almost perfectally or you will have a rich idle problem. with the base plate off the carb can you see any air gap or with the baseplate between a bright light and your eyes can you see any light around the edges of the secondary valves? if so you need to make the valves seal better.
the Rochester engineer that i deal with recommends using a product called DAG213 to seal the secondary throttle valves, but the product does not come cheap.

i hope this helps henry @ oles

 

Im sure I bent it back BEYOND where it was before I did the initial bend
It still runs rich..... These QJ's are a real ***** to get running correctly
Roes book says .005.... Its well wider than that

It ran good except for the secondaries before I bent the rod, not rich at all
I guess I need to take it apart again
Ols? where do recommend setting the float?
Stock L-48 Edelbrock Performer 2101

Thanks

 

When you have the bottom section of the carb assembled I've found it necessary to loosen the two screws holding the throttle plates to the shaft and allow the throttle plates to seat themselves then tighten the screws. Our carbs were manufactured before computer machining so there will always be a tiny amount of air flow past the throttle plates...your task is to minimize it and use the idle mixture screw to adjust for the leakage. The .5" for that rod is just a ball-park figure...after you get all the throttle plates seated you need to open the throttle and watch the primary plates carefully...you don't want the secondaries to open until the primary plates are wide open...parallel with the venturi walls. On my carb the primary plates were opening too far and the secondaries were opening too late...the final adjustment of QJets are a touchy feely thing which is why it's so hard to get them working at 100% the first time you rebuild one. After you get to know your QJet (like you are doing) then you start to realize that the QJet is designed to allow every adjustment possible which means that it can be fine tuned to perfection, but that also makes it harder because there's so many ways to screw it up.

 

Sorry for the delayed reply
After taking the advice of all who posted I finally got it dialed in.... It runs flawlessly!

Thanks all!

 

Great! What exacty did you do to solve the problem? My 70 QJ runs like crap. I broke the spring on the secondary adjustment noted above and the carb is now being repaired at a shop.
Thanks,

Fred

 

I adjusted the spring that you broke....
They are very sensitive..

 

I have the same problem with the secondaries how far did you have to adjust the spring. I don't want to go to much. It runs fine but when i jump on it to pass someone it just boggs.

 

Go 1/8'th of a turn tighter and then test the car. If the bog seams a little better go another 1/8'th of a turn and test. I wouldn't recommend going any tighter than this without knowing just how much tension there is on that spring.

If you want to know where the setting is, back off of the tension screw SLOWLY counting in 1/8'th of a turn increments until the air valve just begins to fall open. This is zero preload. A good starting point for tuning the air valve is 3/4'th of 1 turn preload.

DO NOT GO MORE THAN 1 1/4 OF 1 TURN ON PRELOAD. IF YOU NEED TO GO MORE THAN THIS YOU HAVE ANOTHER PROBLEM. GOING MUCH MORE THAN THIS AND YOU RISK BENDING THE SPRING!

BigBlockk

Later.....

 

Thanks BB I know the spring had hardly any tension on it when I looked it wasn't touching so I brought up to touch. I'll try a nother 1/8 as so as I have time.