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Another Best Carb Question?

Discussion in 'The Garage' started by TexasRyanK5, Nov 9, 2006.

  1. TexasRyanK5

    TexasRyanK5 Registered Member

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    Hello all,

    I have a Bone Stock 1986 Chevy K-5 Blazer with a 305ci V8 with 98,500 miles on it. It has had one owner (my step-dad) and now me. This truck is in perfect condition and had perfect maintance, even when set up for storage(been in a storage facility for 11 years, he worked overseas A LOT). Also, it has NEVER been in the mud.

    I am having trouble with the Carb though and passing emissions here in Houston. Aside from the recent Tune-up, I have completely replaced the exhaust system to stock specs. It has the stock Carb: Rochester Quadrajet 4 Barrel with the numbers 17085226 and 0176 HLY on the side. But, I want to completely replace the whole thing with a better carb that will allow it to get the (round-about) same gas mileage and will basically just make the truck stock again.

    Right now, the mechanic is telling me that they don't make that Carb any longer, only rebuilts and I need to find new smaller jets and seats (which he cannot find) and the price for that is crazy if you ask me.

    Problems:

    Its burning too much gas and its idle is too high and the choke sticks time and time again.

    The emissions that it fails are as follows:

    High Speed - RPM 2585

    Pollutant Standard Current Reading
    --------- --------- ---------------
    HC (ppm) 220 1963

    Low Speed - RPM 705

    Pollutant Standard Current Reading
    --------- --------- ----------------
    HC (ppm) 220 508


    Any help with a new choice of Carb and any troubleshooting would be greatly appreciated!

    TexasRyanK5:doah:
     
  2. fireplug

    fireplug 1/2 ton status

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    QJet is probably the agreed 'best' carb. Get a professional rebuild, or do it yourself.
     
  3. obijuan

    obijuan 1/2 ton status GMOTM Winner

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    you have emissions testing??! uh oh... i hope i dont have to get tested, i thought if it was 20 yrs or older you were ok?? anyways a rebuild on a q jet is actually pretty simple if youre consistent at organizing parts and steps. if you get a rebuild kit it has a diagram with it to help you along. theres a shop in san antonio, that specailizes in carbs and rebuilds. the only one in town i think. maybe houston has one close to you.
     
  4. TexasRyanK5

    TexasRyanK5 Registered Member

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    I will look in to that for sure, but any other suggestions would be appreciated!
     
  5. TexasRyanK5

    TexasRyanK5 Registered Member

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    I went and bought Doug Roe's "Rochester Carburetors" and plan to read it within the weekend. Will I understand it within that amount of time...ummm no. But, what little bit I have read has shed some light on a few things. I am thinking about buying a rebuilt one and trying to tune it myself. I guess we will see how that goes...

    I can hear everyone laughing as they read this....:D


    TexasRyanK5
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    It sounds like that's the stock carb, I guarantee that it is going to be set up just about as good as possible. Putting smaller jets in it is only going to lean it out on the primary side, which is not usually a good thing if the carb was setup by GM for your truck. Do you have a way to make sure it's not running lean after changing jets?

    Do a good visual on the truck as well. With that many years on it, make sure there are no vacuum hoses that have fallen off, leak, etc. Make sure all the electrical/ignition components are in good shape, and so on.

    With a sticking choke, mileage, emissions, and performance are going to SUCK. Fix the known problems, (pull it apart and figure out what they are) then see what happens.
     
  7. TexasRyanK5

    TexasRyanK5 Registered Member

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    It is the stock Carb for sure, but I'll start there. But, with a Carb kit? How do you rectify the sticking Choke? Still new here remember...
     
  8. ZooMad75

    ZooMad75 1/2 ton status Premium Member GMOTM Winner

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    I'd stick with the q-jet you got. It shouldn't need any adjustments to the rods and jets if it is original. GM was pretty good setting up these carbs when they were new, so as long as the engine hasn't been swapped out for something other than the original size, the carb adjustments shouldn't change either.

    Like others have said, make sure the rest of the engine is running right. Poor ignition = unburnt fuel and high HC readings. The choke is there for cold fuel enrichment so if it's stuck its going to run richer. Plus it's been stored for a really long time right? Who knows what the fuel sitting in the bowl has done to the gaskets, needle and seat, float and such. Sounds like a time for a rebuild. Plus if it's sat for a while it's highly possible the casting plugs are leaking in the bottom of the main body. That makes the mixture rich too and its something that won't go away by leaning out the idle mixture screws or changing jets/rods.

    Good move on getting the Doug Roe book. Its worth it. Don't forget to look the entire carb over once you get it apart for leaks. Keep yourself organized because there a lots of parts to a qjet you don't want to loose. Use a baking sheet or similar tray to set the carb in and take it apart. the sides will help keep the little parts from falling off the table.

    Oh and if jets/rods and hanger's are needed for adjustments, Edelbrock does carry *some* for tuning of it's q-jet carb line. (be ready to get bent over on cost though, they are not cheap)
     
  9. mikras1

    mikras1 Registered Member

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    For the emissions - you say you replaced the exhaust - Does it still have the original (flat) catalytic converter?

    If the Carb and ignition are good, you can try retarding the timing a few degrees add some gas tank antifreeze (drygas). But if it still fails - replace the cat. I replaced mine when nothing else would get it thru emissions and the numbers came way down.
     
  10. TexasRyanK5

    TexasRyanK5 Registered Member

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    All this is great stuff that I will definitely check on.. As far as passing emissions...well we all know of someone who isn't me that can pass it. I am just more concerned with getting the darn thing to run correctly. Its always hot in Houston (except for humidity), so I am guessing once I finally get it set right it should be ok? Without having to tune it for the season changes?

    BTW, I am just using the truck as a daily driver to work and back 5 days a week (total round trip 10mi max).

    I'll go more power, bigger, and higher when I have learned a little more about how its supposed to operate while stock.

    Thanks all,

    TexasRyanK5
     
  11. TexasRyanK5

    TexasRyanK5 Registered Member

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  12. ZooMad75

    ZooMad75 1/2 ton status Premium Member GMOTM Winner

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    You wont see them until you get the carb apart. Once you have the throttle plate removed, flip the main body of the carb over. Then you should see 4 of them. I could have swore the book goes over this, but I don't have a copy near me to look at.

    The plugs are like mini-freeze plugs you would see in the side of an engine. Just smaller like 3/8" or 7/16" diameter. They are used to plug passeges that are drilled out in the manufacturing process. they are only pressed in. Don't try to pull them out as you will most likely destroy the carb in the process and then wouldn't be able to get the plugs in the first place.

    After you are done removing all the parts for the cleaning and have cleaned the main body then you can seal the plugs up. Make sure you have the fuel residue clean out good in this area since it does not mix well with JB weld. Once clean, whip up a small batch of JB weld and cover the ends of the plugs. let the JB weld cure before proceeding.

    As a matter of fact I have to do this operation to the Q-jet in my Father-in-law's 77 Pontiac. Dang thing leaks enough fuel through the plugs the float bowl is dry after sitting over night. Makes it a real pain to start without first priming the carb. It's the original carb too so I know it's never been touched.
     
  13. TexasRyanK5

    TexasRyanK5 Registered Member

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    Thanks Buddy.
     

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