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Quadrajet rebuild

Discussion in 'The Garage' started by lochenjons, Feb 15, 2007.

  1. lochenjons

    lochenjons 1/2 ton status

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    I gotta rebuild my rochester qjet tommorow. I know the basic idea but I've never rebuilt a carb before. I found a few links on here that had some good info, and also a google search helped some. But do you guys got any advice/links/instructions/random info I could use?
     
  2. 1977k5

    1977k5 3/4 ton status Vendor

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    Follow the instructions, pay lots of attention to how you take things apart and try to keep them in the order you took them out of the carb. If you have a digital camera, take pictures at each step. That way you can always look back at the pictures and see how it was. Good luck :D
     
  3. LVJimmy

    LVJimmy 1/2 ton status

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    Linkage is the worst part.
     
  4. Cornfield creations

    Cornfield creations 1/2 ton status

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    pick up a good book, I got Cliff Ruggles book on modifying and rebuilding. He explains it very thorough and tells you the main reasons why a Qjet rebuild usually doesn't work properly. I am rebuilding mine at the moment waiting for my high performance rebuild kit and throttle bushing kit to come in.

    www.cliffsqjet.com
     
  5. lochenjons

    lochenjons 1/2 ton status

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    Is there anything I sohuld look for in a rebuild kit? Whats bad about the linkage? Basically all I'm oding is taking it apart cleaning it real good and putting it back togethor with the new parts from the kit right?
     
  6. 1977k5

    1977k5 3/4 ton status Vendor

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    Pretty much any rebuild kit should be fine. The linkeage isn't really that tough to deal with, just make sure you don't bend any of it. Yep, for the most part you are just taking everything apart, cleaning everything REALLY well (finished by running compressed air through all the passages), and reassembling it.
     
  7. Ressurection

    Ressurection 1/2 ton status

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    It's been quite a while since I re-built mine, but it was pretty simple. One thing to check is if the various pins/rods going through the throttle body are 'snug' (in other words they don't wiggle). I had my TB re-bushed by a carb pro because I was getting alot of blow-by that was causing sputtering on accelleration. That move made a world of difference.....'72 w/ 70k on the original 350.
     
  8. chalet2506

    chalet2506 1/2 ton status Premium Member

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    Blow-by is a throttle body problem? I thought it was caused by your rings becoming worn out.
     
  9. lochenjons

    lochenjons 1/2 ton status

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    Alright I'll take a ton of pics and I'll try and post up a write up or something up when I'm done and hopefully I wont screw it up too bad
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

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    What he means is he had a vacuum leak because the throttle body was worn around the primary throttle shaft. :)

    My advice is to not screw with the choke at ALL. Resist the temptation to take it apart and mess with it. Q-jet choke problems are IMO the number 1 hassle people deal with. There is NO reason to take one apart in a rebuild, unless you know with absolute certainty it does not work because something is broken.
     
  11. Ressurection

    Ressurection 1/2 ton status

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    Correct, I meant the vacuum blow-by.
     
  12. Cornfield creations

    Cornfield creations 1/2 ton status

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    clogged idle tubes are a big reason for rebuild not to work, usually crud built up inside the idle tubes passages. Throttle bushings are needed for most carbs because of the wear shafts induce on the base plate. If you have any side to side movement in the shafts you need bronze bushings put in.
    You can get unpredictable tuning if there is movement because of a vacuum leak around the shafts.

    Also on the top second flaps on the air horn there is a plastic cam lobe that is almost always bad, worn or cracked. That should be replaced always, and also the float too. Most kits don't come with all the parts for a really good rebuild, like accelerator pumps, floats, idle tubes, cam lobe and so on.

    Also if you a late model carb you will need to dig out hardened metal plugs covering the idle mixture screws in the base plate if it hasn't been done already. Vacuum test your choke pull off and replace as needed.

    There are lots of different things needed to be paid close attention to to do it right, thats why I say get a good book that can guide you through it step by step, and offers tips along the way like idle tube removal and integrating idle air bypass into your carb if it doesn't have it already.
     
  13. lochenjons

    lochenjons 1/2 ton status

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    Alright I finsihed the rebuild and that was definately not as bad as I thought it would be. the pics I took suck, apparantely my crappy camera cant take closeups. So they didn;t help much but I was able to figure it out. Only problem, I have two philips screws left over and I dont know where they go. All the other screws were flathead so I'm kinda stumped at where these were supposed to go. I wont be able to test it out for awhile anyways because the rest of the engine is apart
     
  14. dyeager535

    dyeager535 1 ton status Premium Member

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    Two phillips IIRC go on the underside center of the carb.
     
  15. lochenjons

    lochenjons 1/2 ton status

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    Uh oh, I put two flat head screws there :doah:. I knew I'd mess this up somehow. There's the 7 screws taht go into the top, the two screws on the bottom. Where else are there screws?
    EDIT: Actaully I do have the philips on the underside...but I still have two short flat heads I dont know where they go
     
    Last edited: Feb 17, 2007
  16. dyeager535

    dyeager535 1 ton status Premium Member

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    Again IIRC (been a few years since I took one apart) if they are flat heads designed for a countersunk hole, they go in the primary venturis of the carb.
     
  17. lochenjons

    lochenjons 1/2 ton status

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    Alright I put everything back togethor and it wont start. It must not be getting fuel since itll start for a bit by putting gas directly into the carb. Gas comes out of the fuel line when I disconnct it so I know that works. There must be something blocking it maybe inside or where it goes into the carb? Or???
     
  18. LVJimmy

    LVJimmy 1/2 ton status

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    Did you use the fuel filter in the carb inlet? If so is it in backwards?
     
  19. lochenjons

    lochenjons 1/2 ton status

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    I did, I didnt take that apart or do anything to it since it woulndt come off easy so I didnt bother. Maybe I should have :doah:. I guess I'll try to take it off again and see if theres something obviously wrong. I'm sure thats the problem I just dont know how
     
  20. dyeager535

    dyeager535 1 ton status Premium Member

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    It usually takes a bit for the fuel pump to get fuel back through the lines up to the carb.

    I'd say one float bowl of fuel would be a good enough amount of running to get it up to the carb.

    *If* the filter is in there correctly already, it really can't block flow, it unseats itself and is simply bypassed by the incoming filter. I would recommend changing it, but be careful getting the fuel filter housing nut on, as they tend to strip easily. Remove it after removing the fuel line.
     

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