I had a 670 Truck Avenger on a 350 in my FJ40 with stock tranny, trans, 4.10 gears and 33" tires.
It made great power. If you want tire smokin' performance, this is it.
If you want low end crawling torque, or any semblance of economy, forget it.
The 670 Truck Avenger cannot be leaned out much more than one full jet size on the primaries. Going two jet sizes cause a lean condition during highway cruising, with intermittent backfiring through the carb. This carb was made for those who want performance and to hell with all other considerations.
The secondaries, as manufactured, are about ten - yes ten - jet sizes too large. Probably to compensate for the very low 5 hg power valve. I jetted mine down 8 sizes with no ill effect.
Fuel mileage was about 8 mpg. Period.
The 470 TA is a better choice for basically stock engines. Better lower end response. And it will feed plenty of fuel and air for most engines in the 300 to 400 cu in range, unless they have big valves, big ports and a big cam.
One problem I had was the secondaries were seldom used. The fuel would constantly boil in them. Eventually this cooked the fuel inlet needle. When I got on the gas, big stumble or even killed the engine because no fuel.
Was going to put a 470 on, but came across a deal on a nice Quadrajet off of an early 80's 350 Corvette. Low end torque and crawling is almost as good as a straight six. I can do 2nd gear starts. And crawl up moderate hills in second gear. There was no way to do that with the 670 TA. Yes, there is a big difference in performance. The QuadraJet only makes power when the secondaries really come on line. But hey, the low speed performance and 10 to 12 mpg makes up for that. That's a 20% to 50% increase, depending on conditions.
Keep in mind most engines are over-carbed. If you look at a realistic red line of 4000 rpm, you'll see the carbs are in the 400 to 550 cfm range in most cases for a mid size V8. Few people are out running a SBC at 5500 RPM in a 4x4.
As far as tuning a Q-Jet, all I did was adjust the idle speed and idle mixture. If you need help with jetting, rods, etc., you're pretty much on your own. That's one plus for the Holley, but the caveat is trying to make a silk purse out of a Truck Avenger. Again, they are NOT economy carbs. You'd be better off getting a simple smogger 600 cfm and putting the spring loaded off road needle and seats in it, and extending the fuel bowl vent stacks with fuel hose.
Another carb not mentioned is the 2-bbl Autolite 2100. These are dirt simple and uber reliable. They work at amazing angles stock. There are no secondaries to worry about. They're not fuel thirsty. They do come in different CFM ratings, so you have to look on line to see what markings on the carb body would be the one you want.
A 600 cfm holley vacuum secondary should be enough for your needs However if you get the Q-jet for your engine you probably will not need to do more than set the mixture screws and drive it
I would recommend an Electric choke on whatever you choose. Oh and buy a new carburetor so you won't have to deal with used carb gremlins.
Run away!
I hope you have good luck w/it.
