Almost all the qj that are numbered 170xxxx are the larger ones.
They are all emissions carbs and set up to run very lean. Great if your after gas mileage. The primary side flows around 230 cfm.
Here is one on a factory 1966 pontiac 230cid OHC six

 

Those fascinated me when they came out....kinda a "WOW!" thing.

 

I wanted to post a summary of my findings/opinions of the Quadrajet. I have been working with them for over a year now, two different models, both post 1975 models with the Ajustable Part Throttle adjustment.

The first (actually the second, b/c I accidentally drilled thru the bowl of the first), was oem to a Chevy truck with a 350. Try as I may, with the guidance of a life long QJ guru, I could not tune it to my Ford 300. Finally I gave up and thought that finding a QJ oem to a 301 would be the ticket; having the GM restrictions, etc., in place for a similar displacement engine.

With the new carb I can not get it right. I have changed jets, m.rods, float level, and 4 thousand other adjustments possible on the QJ, and still normal driving smoothness eludes me. With the $ I have spent on these two carbs, I could have bought 1 1/2 new Edelbrocks, easily. With the time it took to find them, rebuild, and make untold changes, each requiring a removal of the top, I could have rebuilt two engines ... and yep, still I can not get it to run right.

All this is after reading a book, a book! about how to rebuild one of these things!! I also have spent untold nights reading online articles about how to tune them. Cliff Ruggles is the author of the book I read ... several times. He said he could tell was wrong in seconds. He has spent 30+ years working on QJ's. Do I want to spend that long working on them? No thanks. I'm going back to the beloved Autolite 4100.

 

What a hassle! With all the work you've put in, I wish you had had more success, you definitely deserve it.

Sorry to hear you could never get the kinks worked out.

 

Yeah, what a pisser. Probably why QJs have a bad reputation. Runs as well as a Chevy is capable until it needs a rebuild, then it gets swapped for a parts store remanufactured that isn't 100% correct and it never runs right again until it gets swapped for a Holley.

 

It's just been an endless series or probs. When I realized that I had been reading about the QJ for untold hours, and working on it off and on for almost a year, I just couldn't go any further. It was the girlfriend who flirts with one too many guys. Finally, no matter how good she was bad, you just do a burn out and leave her.

 

And people say there's nothing philosophical about QJ's!

I've got the same dilemma. I've got a rejetted Econ-O-Mizer and a locally reworked QJ, either of which I could put on top of my Offy, but I wonder if I'd be better off to just go with a Holley or Autolite and be done with it? :/

 

I used an Economizer for a while...other than the jets, there is little to none adjustment in them and it had a stumble when moderately cracking the throttle. AB used that carb for a while and experienced pretty much the same thing.

 

QJ's are so engine specific it is difficult to dial them in w/o drilling orifices.

I would say to use an autolite 4100, or an Edelbrock. If mpg is an issue, I'd say use the Eddy. The Holley 390 is nice, I've heard (no experience there), but takes some time to dial in to a 300.