Qjet Question
 

I am having a problem with my Q-jet on my footbrake street car and I could use some advice on how to fix it. I have a nova street car with a sbc/t350 combo that I drive and bracket race. It has a stock valve body with a shift kit and I use a Q-jet. I leave at 16-1700 and it flashes to around 25-2800 and it shifts on its own if left in drive or second. It runs low 12's to high 11's. The problem that I have just started to experience is if I have caught someone early in the run and try to pedal the car it starts to slow down like you took your foot off the gas! But it is on the floor. On this particular run I pedaled once at about 1000' and lost .30sec,12mph and lost the rd! The engine makes a different noise like it is straining but still running but just not pulling. Any idea what this might be in the carb? Could the secondary flap close and get stuck in the closed position? Any idea what this is and how to fix it? I have not modified the linkages at all, and only have done the usual things to rebuild and set it up to run on the car and leave clean without a bog etc. Any advice would be appreciated. Thank you

Re: Qjet Question
 

Choke mechanism allowing choke plate to pop shut and, in turn not allowing secondaries to open when back on the throttle?

Re: Qjet Question
 

Check the rear flap. Maybe hanging shut somehow.

Re: Qjet Question
 

Thank you all for the suggestions. The choke is wired open and it does not serve any function. I will look and see if somehow the secondary flap is getting caught on something. Please keep any suggestions coming. Thank You.

Re: Qjet Question
 

The secondary air flap is controlled by the forward located choke pull (air valve dash pot / secondary dampener ) . This will not allow the flap to open after a high vacuum for a second , so it sounds like normal operation . The size of the air bleed restriction inside the pip controls the time it takes to open .
Got this from Doug Roe' s book Rochester carburation H.P. Books
...Trevor

Re: Qjet Question
 

Is your linkage reworked to the secondaries or still factory stock. If still stock, could the rear throttle blades somehow stick closed when you pedal?

Re: Qjet Question
 

Not sure of the exact problem here, but I would say to look at each possibility.
Start with the sec. flapper, and make sure it doesn't come anywhere near the top opening.
You can loosen the screws and shift the plates around a bit, and then re-tighten.
Or, just file the casting a little bit, where ever it's close.
Of course, you wouldn't want to do this on a S/SS carb. I'm sure you know this.

Re: Qjet Question
 

Just remembered this. I once had the split pin that secures the cam for the hanger walk out slightly and that interfered with the flap.

Re: Qjet Question
 

What's the float level measurement? And fuel pressure?

Re: Qjet Question
 

Had this problem approx. 30 years ago. What happens is that when you shut the secondary throttle at high vacuum the pressure across the throttle blades holds them in place when you try to open them again especially if the bores are a little oxidized and the actuating lever is NOT PINNED TO THE SHAFT. The fix is to pin the throttle shaft to the actuating lever; do not rely on the torsion spring to open the throttle. A $.10 rollpin is most common fix.