car stumbles in the air!

[Ed Wright]

Hmm, sounds familiar. Re-check all your grounds. That was my problem.

[TinSoldier 3215]

Thanks Ed.

[Jeff Niceswanger]

Just to be sure its not a fuel issue, put the .149 ( bigger) needle and seat in the carb at the same float height as the previous ones. We have had that same issue before. If it gets alot better or cures the problem, you have a supply problem

[Gary Parker]

when I had this problem, it was a bad regulator. I also just discovered a bad gauge. Sounds like it is running out of fuel to me. Check the flow from the out side of the regulator Gary

[TinSoldier 3215]

Gary, We have put a brand new regulator on and it did not help. Thanks

[Jeff Lee]

A Q-Jet has a very small float bowl. So does my Autolite 4300 series carb. Fuel pressure is one thing, volume is another. And it is volume you need to be concerned about. Excessive pressure can cause it's own problems by spraying fuel out of the seat assembly instead of flowing out of the seat assembly. Think garden hose at a set pressure and being wide open and then placing your finger over 75% of the outlet. You have less fluid control although at a high pressure.
I've seen some pretty innovative ways to take care of the volume issue. One is the use of a large billet type fuel filter (with the filter discarded) placed right before the carb inlet. I have that on my car. This serves to increase the bowl capacity by having a reserve of fuel with a faster response time to the needle and seat). I also have a larger seat and a float that is physically smaller and heavier than OEM. Smaller ads more fuel volume in the bowl and heavier makes the float ride the waves smoother for better needle & seat control. Think wave runner boat as opposed to U-boat.
When you race your car, the biggest draw on the fuel system is when you launch and the load is heaviest when doing a wheelie. Burnouts offer the least amount of load and the trip on the track is progressively more demanding the farther you go. Your fuel system will recover from many faults as you go down track but the launch is the shortest and hardest load.
I'm know Q-jet racing expert but I would say I think 7#'s of pressure is border line excessive. I've seen racers go faster with less pressure; back to that garden hose example. You also need to make sure the basics are there, adequate pump, adequate pump pressure, adequate fuel line sizes, adequate fuel cell or tank fluid control.
But yes, I will concede a bad electrical switch or ground will also cause problems.
So to test further, can your car wheelie without the trans-brake? It should. Try it without the t-brake and see what happens. If it still stumbles, then it's a fuel issue. If not, I would say look at the electrical items.
Can't wheelie without the t0brake? Then throw a couple of bags of something or 4 BBC cylinder heads in the trunk (secured of course) and see what happens when you launch it foot-braking it. Just go to the 330' as that's all you need.

[Richard Grant]

7lbs. is a lot of pressure for a quadrajet. I am surprised that you don't have other
problems. Try 5 or 6 and if it doesn't affect the et you will be better off in the long run. It might even help with your problem.
I don't know who does your carbs but some carbs will stumble coming off the trans brake. Try a carb from different builder, someone who has a track record of building quadrajets using a transbrake.
Also are you on a chip when you leave, some quadrajets don't leave well off a chip.

[TinSoldier 3215]

Mr. Grant, We leave at 4,000 of the rpm's.

[Bob Mulry]

Hi,

Just a heads-up on the adjustable type transbrake buttons......

Some of the "adjustable" buttons have the return spring set as to be the softest possible and the weight of the button and plunger along with the additional "G" force of the launch are enough to slightly depress the button and cause a miss.

They have to build it this way to allow the plunger to return as slowly as possible to the top of travel to allow adjustability..

Put a different button in or if it's OK reinstall your old button and give it a shot...

Bob

[Tod Lane]

Stalling the fuel in the line? Fuel line too big maybe?