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Discussion in 'Chevy Trucks' started by 84 chevys, Mar 4, 2004.

  1. 84 chevys

    84 chevys Junior Member
    from florida
    Messages: 2

    got a question. i drive a 84 k10, 350, 700-r4, 35's and 3:08 gear. gas mileage aint all that bad, but theres always room for improvement. right now i run a holley 600. if i were to change to a edelbrock q-jet spread bore, would that help out much?
    the only one i can seem to find with an electric choke is a 795cfm.
    is that to much carb? ive gota mild 350 and love it, but was afraid that may just be to big. any information would be appriciated, thanks.
  2. ratlover

    ratlover PlowSite.com Addict
    from IL
    Messages: 1,325

    35's are what is killing your milage. 308's are a bit too much gear IMO with the 35's. The 308's and 35's aint doing your trany any favors either.

    Q jets if tuned right give better gas milage than other carbs. Good for low end response too. Is your holley a vac sec carb or is it mechanical? is it spread or square bore? 800cfm is technicaly too big but if tuned righ you can get it to work just fine. An edelbrock performer is a good crab too but unless your carb is really outa whack your milage problems aint from that. Its your tires/gears and the rest of your truck.
  3. 84 chevys

    84 chevys Junior Member
    from florida
    Messages: 2

    carb is holley 600 vac. secondary, square flange. several people sugested i put a spread bore q-jet in its place. i like the holley it does a great job but ive been pndering the idea of swaping it out and see what happens. gears are also in the works. ive run these tires and wheels for a long time and have never had any drivetrain problems to speak of. its alot of truck and i pull 12.5 mph on the highway., sometimes a little better.
  4. ratlover

    ratlover PlowSite.com Addict
    from IL
    Messages: 1,325

    The quad is a good carb but I dont think you will pick up a ton but swapping it. I'de recomend ditching the gears or the tires. If your going to ditch the gears hen swaping axels(like for 3/4 ton stuff) is ussualy cheaper/easier and you get beefier parts.

    I'd do the gears first becaus eyou will probably ned to tweak the carb a bit with the different gears anywho and I really dont think its the prob.
  5. 75gmck25

    75gmck25 Senior Member
    Messages: 119

    You can get the Edelbrock square-bore quadrajet, #1406 at just about any auto parts store for about $260. Its a 600 cfm carb. with electric choke, and its supposed to be tuned for economy.

  6. ratlover

    ratlover PlowSite.com Addict
    from IL
    Messages: 1,325

    the 1406 isnt really a true quadrajet. its the old rochester design I believe that edelbrock bought out but its not an actual quad. They are pretty good economy carbs and easy to set up but they dont have the primaries that are as small compareed to a quadrajet. One of the reasons quadrajets work really well is that they have tinny primaries that you are generally running off of so it acts like a very small carb till you get on it and the secondary kick in. The square bore refers to the fact that the primaries and secondaries are the same, although you guys probably know that......
  7. jbrow1

    jbrow1 Member
    Messages: 76

    A 350 with 35's will get what it gets for mileage I'd think. Ya can do this or do that, but for the pennies you might save it's not gonna be worth it. The only way to save gas with one of those is to stay off the gas. I drive an 86 gmc with 4.10 gears, 350 motor, 400 trans, and run 33's. Leadfooting takeoffs will eat the gas, as will high speed driving. But, ya gotta pay to play.
  8. nachoschevs

    nachoschevs Member
    Messages: 58

    I agree with ratlover, the 38's and the 3:08 combo is what is killing your mileage. It makes the motor burn lots of gas to get them big tires turning. It would be cheaper in the long run where fuel is concerned to look for 3:73 or 4:11 rears. My 82 was the 3:08/305 set up and it was a real dog. I put in 3:73/350 now and it has power and if you stay out of the pedal like jbrow1 said then your mileage will improve. I believe it gets better mileage now since it don’t have to work harder to turn the tires. Plus it is a good enough reason to go to 3/4 parts.
  9. Hankster

    Hankster Junior Member
    Messages: 16

    Somebody sounds a bit confused !!! A Quadrajet is a true spreadbore...the "only" one made if I remember right....
    The 1406 SQUAREBORE you refer to is a remake of the CARTER (NOT Rochester) AFB 4 barrel....the 1406 will flow 600cfm......the Quadrajet will go 750 cfm.....but is "self adjusting" in the way the metering works..which is why they were used on so many different size engines over the years.....the Quadrajet is way understood and underrated....if more guys knew how they worked...a lot less carbs would get "swapped"....
  10. ratplow408

    ratplow408 Member
    from PA
    Messages: 33

    My 84 blazer had a 350/th350 trans 308's and 35's. I swapped to 410's and brought it back to life. The milage was 12-13 mpg. It had an Edlebrock Q-jet 1904(electric choke).The 1904 is 795 cfm,I belive the stock Q-jet is 750.Both carbs are for use on 305 to 454.The Edlebrock Q-jets are expensive. About 1/2 as much as Holley.I've had luck w/ both. If you do alot of offroading get a carb w/ center hung floats.See above about "Leadfooting"!