Honestly, I couldn't care about mileage and all of my engines agree with me. LOL.
Except my 400. It is tuff on gas with a high ratio rear and moving nearly 4000 lbs minus me and gas. I had a Carter 750 on top awhile ago when I had a T-Q problem. It wasn't the carb for it. The T-Q defintely is. Being a low comp. ratio smog engine, it would have like a 600 - 650 carb better. The small primarys of the T-Q make it work great for a wide varitiy of engine sizes and power levels. Divabilty went through the roof by compare to the Cater 750.
I had a 318, lightly pumped up. At the time it was running a Carter 625 emmission carb. Accelerated well. Swapped out to a borrowed AVS during the AFB teardown to find a problem. Turned out to be a dirt cloging thing. The tunable air door really woke it up.
I was wondering the same thing as you also. One day at a swap meet I seen a bunch of fellas unloading parts off there pick up to sell. I spotted the T-Q on the floor and inquired. He said $25. What the hell. A $30 kit and a home rebuild later....Whoa! With the swap, it just seem to keep wanting to climb higher and higher. Un-tuned and rich, that very night I took out a Camaro that had previously beaten me. YEP. Happy I was.
That carb later went on a 360 with a fair amount of "PEP" built into it. Being the engine was larger, it worked better. The T-Q was the larger one with bigger primarys. Since the engine had a notable power increase in Tq. & HP over the teen, the carb worked even better. Very throttle responsive, ran and drove well. With the best part of wacking the long pedal to create the famed "MoPar" sound. Indeed, IMO, it was the carb to have on this street strip engine.
(Gas mileage was about 16 and 7 depending on driving around or putting the 4bbl.s to work. <LOL> )
The T-Q has alot of little adjustments and measurements to hammer out before you go out and flog it. Set it up, take your time and I do believe you'll like it. There not the easiest thing in the world at first.
The only thing I dislike is tuneing parts. Rods and jets. Hard to find sometimes and the numbering system on them is very close to ancient Chinesse hi-ro glifics (SP, sorry, the old way Egypt used to write, like in the pyrimads, picture symbols. OK, I went to high school very hi, <LOL> )
What I do in the mean time is to use the MUCH longer AFB rods to get it in the ball park of idle and then find out what the T-Q rod equal is. It is a pain, but I put up with it. You can bend and cut the AFB rod to make it work. Not my fav thing to do, but it works. Just make sure the rod is straight when you use it after you bend it to fit.
The other Carter carb I like is the AVS for performance. The AFB will make a decent driver carb and a OK performance carb. The problem is IMO the secondary air doors counter weight. It can be made to perform. But a twist of a screw driver is easier and quicker to dial in the secondarys than lightening the counter weighted air door. Which requires ethier drilling a hole in it or shaving down the doors counter weight to make it lighter. Then when you take to much off, how do you put it back on. Enter more parts from the store. (Wrong!)
