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Q-jet Question

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Mastiff, Jul 9, 2003.

  1. Mastiff

    Mastiff 1/2 ton status Premium Member

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    I'm running an Edelbrock performer right now, which is okay (very powerful, but lousy throttle response and sometimes hard to start - especially after a few days). I still have my old Q-jet sitting in a box, which had nothing really wrong with it except for all the emissions lines hanging off of it.

    Can anyone tell me if a Q-jet from a 1983 305 is a good carb if I'm not interested in any emissions stuff? Can I just plug up a bunch of the vacuum ports and have a normal good Q-jet? Or should I plan on having it rebuilt for my non-emission 350?

    Also, any idea if it'll still be good to go after 6 years in a box in the garage?

    Thanks.
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    The later Q-jets are good carbs IMO. This one has no electrical plugs on it except the choke?

    FWIW, all '83-84 305 Q-jets I've seen so far are 800CFM units, which really isn't a good thing IMO for a "smaller" motor, but they work fine.

    To get the best economy out of it, it probably will need to be re-jetted/rodded on the primary side, but slapping it on it will more than likely work fine.

    As to sitting, well, it probably will have a bunch of garbage in the float bowl that can cause havoc later, so it would be *best* to get a "rebuild kit", and replace the gaskets and clean it out.
     
  3. Mastiff

    Mastiff 1/2 ton status Premium Member

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    Yeah, it only has a wire for the electric choke.

    Thanks for the info. Maybe I'll just slap it on there... I'm not sure. I don't trust myself to rebuild and/or rejet it properly. Maybe I'll look into having it done over professionally for my 350. Know of any good places I could mail it off to?
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    [ QUOTE ]
    I don't trust myself to rebuild and/or rejet it properly.

    [/ QUOTE ]

    Go buy yourself the $20 kit at autozone (or whoever is you preferred parts dealer) and sit down and try it. Lots of people here can help you through it, or you can buy the book "rochester carburetors" by Doug Roe. Been a long time since I looked at it, perhaps someone else can comment on whether it has a tear down/rebuild section? Not sure if the Haynes manuals do either.

    It's actually a simple process to tear it down, inspect, clean, and reassemble. I'd probably attempt a tear down instead of trying to run it as is. I've had too many of these things apart after they've been sitting to say otherwise.

    No clue who you could send it to, but the cost is usually pretty darn high. You could try www.carbsunlimited.com and find out what they get for a rebuild. I've purchased parts from them (local to me) but I've no experience with their rebuilds.
     
  5. Alaskan85K5

    Alaskan85K5 Registered Member

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    I purchased a rebuilt off e-bay from a guy in texas. He did a heck of a job, basically the same work Jet does on these things and at 1/3 of the price. Here's his info if you want to talk to him.

    Carburetor Of Texas
    2100 S. Great SW. Pkwy #503
    Grand Prairie TX 75051

    e-mail carbs101@mindspring.com
     
  6. SkulzNBonz

    SkulzNBonz 1/2 ton status

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    I just rebuilt one for the second time ever and it really isn't hard. The instructions that come w/ the rebuild kit are pretty easy to follow. If you don't feel comfortable doing it yourself, you should be able be able to find a reputable shop local to do it for less than a C note.

    John
     
  7. RustBuket

    RustBuket 1/2 ton status

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    I am 17 yrs old and have never done any engine work before. Last fall I started a rebuild one a 305 using only a book as my guide (my dad knows nothing). I also took the carb apart with no instruction, I would say the only hard part about putting it back together is the choke assembly. Just watch how it comes apart as there is a few moving peices that need to go back together the same way for it to work. Maybe make a diagram. Good luck.
     
  8. Mastiff

    Mastiff 1/2 ton status Premium Member

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    Okay, I just got the ol' Q-jet out from the garage. I already have a question:

    It looks like the guy who last rebuilt this has wired something up in a way not originally intended by the manufacturer. There is an arm on the back of the electric choke that looks like it will prevent the secondaries from opening while the choke is still cold (?). He has this wired up to the bottom of a screw to keep it from functioning. Does this make sense, and is there any good reason to leave this, or should I cut away this wire and let it operate as designed?
     
  9. dyeager535

    dyeager535 1 ton status Premium Member

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    That's the secondary lockout lever. Designed to keep the secondaries shut when the choke says the engine is cold. Not a bad setup, never had a problem with it myself. However, it *is* another piece that can cause problems, so I'd probably leave it alone. Probably run like garbage if you are heavy on the gas before the truck warms up, but thats the only real concern, except higher emissions as well. But again, that would only be for cold engine operation, which you wouldn't get tested on anyways.

    If visual inspection, that might fail you, but not sure how obvious that would be.
     
  10. Mastiff

    Mastiff 1/2 ton status Premium Member

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    [ QUOTE ]
    That's the secondary lockout lever. Designed to keep the secondaries shut when the choke says the engine is cold. Not a bad setup, never had a problem with it myself. However, it *is* another piece that can cause problems, so I'd probably leave it alone. Probably run like garbage if you are heavy on the gas before the truck warms up, but thats the only real concern, except higher emissions as well. But again, that would only be for cold engine operation, which you wouldn't get tested on anyways.

    If visual inspection, that might fail you, but not sure how obvious that would be.

    [/ QUOTE ]

    No emissions here in Iowa. /forums/images/graemlins/laugh.gif

    So, this carb will have a large number of plugged vacuum ports... /forums/images/graemlins/wink.gif

    I've got the thing broken down according to my Haynes rochester carb book instructions. It's not totally apart, but it's in three major pieces with the choke, vacuum thing and various other parts taken off. Can anyone tell me for sure whether it is safe to dunk the three big sections in parts cleaner? I see no soft rubber, but it looks like there might be some hard plastic bushings still in place.

    Also, how do you get the spring off of the accelerator pump? My rebuild kit has the rod with the rubber base, but not the spring and little spring holder (does that make sense?).

    Thanks.
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

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    [ QUOTE ]
    Can anyone tell me for sure whether it is safe to dunk the three big sections in parts cleaner?

    [/ QUOTE ]

    As I recall, if you don't see any rubber/plastic, there isn't. one thing to be careful of, is the cam for the secondary air valve. Tends to get brittle, so I bet cleaner would be no good for it. Never pulled mine, but I always used paint thinner and a brush for cleaning, nothing more harsh. Might be able to pull it out before cleaning, might break though. Should be easy to replace if it does.

    [ QUOTE ]
    Also, how do you get the spring off of the accelerator pump?

    [/ QUOTE ]

    If you can't tell, it's been awhile for me. /forums/images/graemlins/smile.gif Should be able to push down on the top "plate" that holds the spring in place, and slide it off to the side...it's got a slot cut in it, and the accelerator pump shaft has a narrower section that will allow it to slide off.
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

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    BTW,

    *COMPARE THE ACCELERATOR PUMP PIECES BEFORE DISASSEMBLY/USE*

    I've seen the wrong ones come in the "correct" kit, and there are multiple variations that could cause problems later on. Compare shaft length, spring "compression" after assembly, etc. If the slot in the rod for the spring retainer is at a different level, you could end up having the spring bind up. BTDT
     
  13. Mastiff

    Mastiff 1/2 ton status Premium Member

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    [ QUOTE ]
    If you can't tell, it's been awhile for me. /forums/images/graemlins/smile.gif Should be able to push down on the top "plate" that holds the spring in place, and slide it off to the side...it's got a slot cut in it, and the accelerator pump shaft has a narrower section that will allow it to slide off.

    [/ QUOTE ]

    This worked. Thanks! /forums/images/graemlins/smile.gif
     
  14. Mastiff

    Mastiff 1/2 ton status Premium Member

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    I rebuilt the Q-jet and it's back on the truck. /forums/images/graemlins/laugh.gif

    I can tell from the test drive that the off-idle response is WAY better than the Edelbrock. I'm not having an easy time getting the idle mixture adjusted though (the Edelbrock was easier). I'm trying to adjus the screws to maximize vacuum, and then back off (lean) just a little. Thing is, the screws don't seem to give much good feedback. Also, I'm not getting as much vac as I thought I was getting with the Edelbrock. Anyone know about how much vacuum I should expect from a 350 with a mild (RV) cam? I'm able to get about 20.

    Also, do I really need that stupid vacuum diaphragm thing on the back right (passenger side)? It appears to limit the choke and the secondaries under vacuum, but it's also interfering with everything (mostly the vacuum lines to the tranny and vac advance). Would I really notice if it was gone?

    Thanks!
     
  15. Mastiff

    Mastiff 1/2 ton status Premium Member

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    Oh yeah, one more thing: any suggestions on how to get the choke setting right? This is an electric, and I lost all reference to how it was setup at the factory. Should it be open at all at room temperature, or fully closed? I'm not quite sure how to even get a reasonable starting point.
     

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