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'85 Q-Jet Power piston ???

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by jms, Sep 27, 2002.

  1. jms

    jms 1/2 ton status Author

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    \'85 Q-Jet Power piston ???

    Another duplicate post, I know, but please bear with me...

    My carb is a M4ME with the dual accelerator pump setup. I may have finally diagnosed the cause of an overly rich condition that caused me all sorts of grief on the way to B'Bash and back (again, thanks to fisher1648, Storm Trooper, and BigBlue76 for your help to get it to run right): the plastic retainer on the power piston doesn't seat right, allowing the spring to push the piston too far up. Result is the piston is stuck in the up position, essentially pulling the primary metering rods out of the main jets all the time - so it's running rich all the time, and mileage is down the dumps, you guys don't want to see my fuel bill for B'Bash! /forums/images/icons/laugh.gif

    My question is: can the power piston be taken apart? Edelbrock sells the retainer, so I ordered it, together with power piston springs and a few different jets (cause I'd like to try and get a bit better mileage after I fix the power system). Of course, now, after looking at the piston, I'm not sure how to install the new retainer. The piston has a cross pin, but I'm not sure whether that's the secret to taking it apart so I can get the plastic retainer on the 'collar'. Roe's Q-Jet book is mute on this one, so if anyone has any info, it's greatly appreciated, thanks, michael.
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    Re: \'85 Q-Jet Power piston ???

    Need one in front of me to double check, but I *think* the actual rod hangar is just pressed into the PP. I wouldn't try yanking it out just on that, but keep it in mind. I almost doubt its considered a "serviceable part" as I don't recall any designed way to get it apart. If the rod hangar portion were to pull out of the PP, you could swap retainers, correct?

    I can play with some I've got at home later perhaps, and see what I can come up with.
     
  3. jms

    jms 1/2 ton status Author

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    Re: \'85 Q-Jet Power piston ???

    Thanks for the reply. Correct, if the rod hanger were to come off, I could install the retainer. I infer from the Roe book (where it sez if the rod hanger comes off, you'd have to put it back with epoxy) that that's not supposed to happen. What I can't tell is if the 'collar' (the round piece around which the retainer is placed, and into which the rod hanger goes) can actually come off the body of the piston itself. I'm considering to put a tiny drop of epoxy or SuperGlue onto the old retainer once I put the carb back together in order to hold it down, or putting a piece of thin gasket paper on the retainer so that it can no longer slip upwards once the airhorn is installed. Since I have only one piston, I'm not gonna do anything to it that would require force. By the way, what's a good source to purchase primary metering rods for a 17085226 carb? Thanks for your help, michael.
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    Re: \'85 Q-Jet Power piston ???

    I don't think I'd trust epoxy or JB weld in that case. Either seem to work perfectly fine to seal the well plugs, but if that piston is continually contacting that retainer, I'd imagine it would eventually break the bond. At least thats my thinking.

    My other thinking is, go get some spare carb parts from the local wrecking yard! /forums/images/icons/smile.gif Power piston would be the same all years that aren't CCC as I recall, and I've yet to break a retainer pulling the PP out. Then you can get spare rods too.

    Don't know if Edelbrock makes primary rods, but I'd not buy them either, you can get spare Q-jets complete, if dirty or a little rusty, for $5 each at swap meets.

    Just some ideas. I'll take a peek at mine when I get home if I remember, and see what I can figure out.
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

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    Re: \'85 Q-Jet Power piston ???

    I just looked at a PP in my garage. I think its a fairly old one, there is no "pin" (APT?) pressed into the side of it, just a pin on the base, and the rod hangar of course.

    Tried pulling the pin at the base out (what the spring aligns on I guess) and it wouldn't budge. Obviously the rod hangars are pressed in, I tried pulling on it a bit, but it didn't move, although I know it would pull out if I tried hard enough.

    Don't see any other ways to "disassemble" it.
     
  6. jms

    jms 1/2 ton status Author

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    Re: \'85 Q-Jet Power piston ???

    Dorian, thanks for looking. I think I'll try and use some RTV to make the old retainer stay seated, and fiddle a bit with the gasket so that the retainer can't move up once the airhorn is installed. Now if only my new jets would come in....
     

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