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Rebuilding/Modifying/Tuning a Quadrajet for Offroad

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by K1Orion, Jan 19, 2005.

  1. K1Orion

    K1Orion 1/2 ton status

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    I'm rebuilding my quadrajet so my junk will run better and hopefully pass emissions. I also posted this on pirate. I bookmarked and read almost everything at http://www.florida4x4.com/tech/quadrajet/ and have done a lot of searching but I still have a few questions. Maybe The CK5 crew can help me out.

    Is it possible to rebush the throttle shaft without a drill press? I need to buy a kit and see what is included (or maybe just buy bushings) and see what the instructions say but I figured I'd ask here.

    I read that setting the float "a little low" will make it run better at angles because it won't load the carb up. How low should I set it? I'm looking for a # here, I found "between .375 and .400 for a street driven car" on the florida4x4 link, but this isn't a street driven car.

    I also read that you can epoxy in a small piece of metal to create a reservoir around the jets to prevent it from starving on climbs. Anybody got any opinions on this? How tall should the "dam" be. Any experiences from anybody who has actually tried this? Is this necesary if you run the carb backwards like I plan to?

    Anybody got any pics of a backwards Q-jet setup? Any tips? Linkage seems to be the only real issue. I already have a spreadbore/square bore adapter to mount it with.

    The rebuild kit I bought has a different needle seat than the ones in my parts carbs, which are all 78-81 truck carbs.
    The ones I have all look like
    [​IMG]
    but the one in the kit has slots in the sides of the seat. What's up with that? Should I reuse the 1 that was in it or use the new 1?

    Any body got any suggestions on what primary jet/rod, secondary rod, and power piston spring to run? It had 073 jets, 51 primary rods, and DR secondary rods. This carb is going on a 80 long bed pickup with 350/465/4.10s and 38s. Motor is stock except for an old aluminum single plane intake and headers with 2.5" exhaust.

    Thats all I can think of for now, I'm sure I'll encounter more as I start puttin the carb back together. Now I'm off to the JY to "accumulate" various power springs, jets and needles to tune this thing with.
    __________________
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    I'd say at the VERY least to rebush the shafts, you want to have the base in a vise. I still doubt you can get the drill steady enough to do a good job. The metal you drill through is SOFT.

    Around here, the price has gone up quite a bit, but a big name carb shop will rebush the primary throttle shaft (only the one bushing IIRC) for $40. It's a lot when the bushings cost $5/pair (or did last I bought them) but then you need the right drill bit (J is it?) and some way to hold it all steady enough to get a good fit. To be honest, the one I did wasn't a very tight fit, but it worked. Probably not as good as it should have, but I didn't notice if it caused any problems.

    The open "slot" jet is what I'd use personally. I don't see how that can do anything but HELP fuel flow in quicker/easier. I played around with one of the ones like you have, and just cut slots in it with a air cutoff tool. :)

    If anything, I would concentrate on getting more fuel into the float bowl, instead of trying to build sumps around them. Somehow make it more efficient to flow fuel...as little filter restriction as possible, higher GPH pump, etc. If you can move enough fuel to keep the bowl somewhat full, then you don't have to worry about it. Besides, if the bowl goes dry, where will the fuel from the secondaries come from? If you need power, you'll need the secondaries, and IIRC, the feed for them is out of tiny holes in the float bowl.
     
  3. K1Orion

    K1Orion 1/2 ton status

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    I looked at jegs and summit and found the power piston springs. $7.99 for the springs, but the "handling" charge was $8.99!!!:mad: $8.99 to put a ziploc with 5 1" long springs in a 3ft. square box full of styrofoam and gay stickers and other propaganda I don't want. I don't think so.:mad: I'm gonna try to find em locally, but I kinda doubt anybody keeps em in stock.

    I was under the impression that setting it low will keep it from loading up at extreme angles.
    Running it backwards helps to keep the primaries covered. Stock, a steep ascent will uncover the primaries when the fuel runs to the back of the bowl. This starves it for fuel and kills the motor, especially at less than full throttle.

    If i'm going down hill, I don't care if it dies, I'm gonna find the bottom anyway.:D

    Was there a difference between the 2, in your opinion?


    Thanks, keep it coming!:D
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    I never actually ran one back to back against the other.

    I was running out of fuel at higher RPM in my car with the Q-jet, I actually just leaned out the secondary rods and that problem went away. If it hadn't, I probably would have gone in and changed that piece.
     
  5. ColAdo82K5

    ColAdo82K5 1/2 ton status

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    Do you really run a single plane intake ? Might think about a dual plane...might help things out.

    Blake
     
  6. thebigdaddyof2

    thebigdaddyof2 1/2 ton status

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    Hey,
    Why don't you run over to Speedway or Tailor's and snag a GM van TBI setup for next to nuthin'??
    Call me, me and Shagz will meet ya there for some Yardin'!!
     
  7. K1Orion

    K1Orion 1/2 ton status

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    Todd, I'm up for some yardin!! I actually went by speedway the other day cause I was off work. I saw a d44 with flattops frozen into a glacier. They might be worth goin back for. I dunno? I still haven't been to Tailor's. Maybe you could meet me someplace, blindfold me so not to reveal its location, and take me to the holy grail of junkyards.
    How much $$$ are you talkin about for a TBI setup?
    Did you start on any projects this winter in the new shop? Maybe a K5 on rockwells or a Toy on 35 spline stuff?

    Blake, I've got a single plane cause the edelbrock name adds 50hp, and it was free. :D I might put the stock dual plane or switch to something better if the price is right.
     
  8. thebigdaddyof2

    thebigdaddyof2 1/2 ton status

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    You could strip a whole TBI setup out of a van for very little money.
    IMO, this would be a much better way to go than investing time and cash into a Q-Jet.

    Projects are slow. I have started on Hustler's axle, tire, bumpers, Rhyno-line project tho. Been workin' on the shop itself a whole lot.

    Let's go yardin soon...and get you sum TBI.
    And you do want to go back to a dual plane intake.
     

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