I have the summit 750cfm carb on my truck and their 500cfm carb on my car and love them both. Easily the best carbs I've run so far. They were actually calibrated pretty well out of the box too right from the factory which was a bonus for me.

 

Ive had Edelbrock, not a fan......

Grew up on Holley.....running one now....

Summit Carbs.....never tried them but with all the current information out there on them, guess it'll be my next one to try.

 

The QJ is very versitile. With its three layer body, it was very easy for Rochester to pop different size orifices into the passage ways, different jets and m.rods, booster springs. That way they were able to install one size carb on any size engine. I personally run an 800 cfm QJ on a Ford 300 I6, and it works great! The tiny primaries flow 220 cfm, and the toilet flusher secondaries are controlled with a vacuum flap that gives the engine only as much fuel as it can use. It takes a lot of playing with it to dial one in, but once you find that sweet spot it's heaven--power and mpg. When I tow or haul, I pop the air cleaner off and turn the part throttle adjustment screw to make the afr mix richer, and turn it back for normal driving. Love it.

 

Wow! That's a lot of carb for that six. You must really know stuff to make it work. I remember my mom's 66 Malibu wagon with a 275 horse 327, I had ad to really stand on the pedal to get the QJ secondary's open.

 

Wow! That's a lot of carb for that six. That is a common misconception. You see, although the QJ is an 800 cfm carb, it will flow that amount only when both the primaries and the secondaries are fully open. That never happens. 98% of all street driving is done on only one side of the carburetor, the primary side. That side of the QJ flows only about 220 cfm. And, since the secondaries are vacuum operated/controlled, I have them crack open just a tad when the rpms reach about 4k. (GM put an 800cfm QJ on its 231 ci v6 Buick Regal).

I had ad to really stand on the pedal to get the QJ secondary's open. All QJ's have a simple spring adjustment to determine when the secondaries open. However, you only want them during passing situations, or moments when you need an extra shot of power. Mine are set so that I can drive day in and day out without them ever opening. I wind out each gear to normal rpms, and shift. But should I wind the rpm's higher in each gear, say 500-1000 rpm higher, then the secondaries will crack open and I get a rush of power, then I shift and do it again in the next gear for better acceleration.