Stumble off idle -

[patrickt]

Originally Posted by Grubby

The Holley 750 ran really well at steady cruise and part throttle. ... The car is no fun to drive with the Quickfuel. It was much more pleasurable with the Holley and my wallet was fatter.

John, you and I are not Morris, we're not even Rick Lake. We don't race our Cobras competitively and, for us, tuning for WOT is over-rated. Personally, I can't hit WOT at low speeds -- she'll just break the tires loose -- and I can't hit WOT for more than two or three seconds at any other speed. In going on seven years with this car, I don't think I've ever held the pedal to the floor for more than three seconds when the car was actually moving. And if I tried to speed shift from third to fourth at 6500 RPM, while holding the throttle to the floor, the next day's discussion would not be whether there was hesitation or stumble, but rather if I get an open-casket funeral or not. That said, what I think you should do is give the QF carb one more weekend of tweaking and monkeying, and then put it in the classifieds here. Put the Holley 750 back on, put the #70 jets in the primary, put the .031 squirters in, orange cam, a 65 power valve, and a black secondary spring -- yes, black. Then carefully set the floats and idle mixture, and see how she runs at part to half throttle. Forget WOT. Only when you have the car running nicely at light to part throttle do you start to change out the secondary spring, going lighter, until you feel hesitation or stumble at the heaviest throttle you can safely hit on the street. Then go back to the spring that was in before that happened. If you do that, I think you can get it so that you are happy 99% of the time.

[blykins]

He doesn't have to put it in the classifieds and take a hit. If he's that unhappy with it, I'll give him his money back.

I would personally never use anything less than an 850 on an engine of this displacement, whether it gets raced or not.

These QFT carbs are certainly capable of excellent part throttle and cruising performance, and I think John has already stated that the WOT difference is very noticeable. He can have the best of the both worlds.

[patrickt]

Originally Posted by blykins

I would personally never use anything less than an 850 on an engine of this displacement, whether it gets raced or not.

But he's got a nice 750 conveniently positioned on his living room coffee table.