Oddball Quadrajet?

Discussion in 'The Venerable Q-Jet' started by TORQUED455, Aug 14, 2018.

  1. TORQUED455

    TORQUED455 Well-Known Member

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    I’m repairing a Quadrajet off of a 67 Impala 327. The carb number is 7037213 with a date code of 2933. It has the newer-style Torx fasteners for the air horn. This would appear to be a service carb built in the fall of 1983. It’s unusual to see no adjustable part throttle system. Any of you Qjet folks ever run across this? I don’t recall if they wet-flowed service carbs back in the day. One of the important adjustments for production carbs on the flow bench was APT. Service carbs got a pass or that wasn’t part of the calibration process I suppose.
     
  2. Bigpig455

    Bigpig455 Fastest of the slow....

    I dont recall seeing the baseplate APT on 4M's until 71, at least on the Buick carbs I've worked on. That said, I've seen some really weird service replacement carbs, they seem to have been built with whatever was available at the time....
     
  3. carmantx

    carmantx Never Surrender

    That particular code should have the large A.I.R. port in the rear of the base plate. The APT in base was added in the 60's on the Quadrajet. Many 66-67 didn't have it and the power piston would not have the bottom pin either. That carb you are working on has the adjustment screw under the triangle cover on the air horn.
    There are many things on that one that isn't correct for a typical 67 unit, choke flap, choke mechanism, pull off bracket,etc. But like Rhett said, if it was a late service replacement unit, or rebuilt by commercial facility, it could have a mix of stuff not correct to the original.
     
  4. lemmy-67

    lemmy-67 Gold Level Contributor

    That's a franken-Q...has the teflon-coated air flap shaft & the wrong year base-plate...probably got lots of random parts elswhere...
     
  5. Cliff R

    Cliff R Well-Known Member

    It's Service Replacement for sure and the Torx headed screws would indicate late production.

    With later production models you'll see a few differences like Teflon coated shafts and the wider spacing for the choke flap/screws.

    They made Service Replacement Q-jets in much greater numbers than the original production units, and they service quite a few part numbers besides what and original 7213 carb would have been used on.

    Another fairly common Chevy SR carb is the 7029207. The original units were for the 1969 350/350hp engines with the manual transmission, but SR's show up all over the place and were even used to replace some of the early Big Block Chevy units......Cliff
     
  6. TORQUED455

    TORQUED455 Well-Known Member

    All good info guys. Yes, it has the large A.I.R. Port in the rear of the baseplate. I’ll take a closer look under the triangular thing on the air horn tomorrow, but I don’t see anything in the 3rd picture. This carb is in excellent shape, which is always a bonus.
     
  7. lemmy-67

    lemmy-67 Gold Level Contributor

    The tiny screw under the triangle plate around the bowl vent is for the primary air bleeds, it can easily pop out & get lost. All it needs is about 1/4 turn in order to change the amount of air which goes into the primary idle passages.
     
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  8. TORQUED455

    TORQUED455 Well-Known Member

    That’s exactly what it is.
     
  9. TORQUED455

    TORQUED455 Well-Known Member

  10. Cliff R

    Cliff R Well-Known Member

    Thru 1969 that screw will lead to the idle system passages and most will have the upper idle bleeds in the airhorn not in the main casting. So basically it introduces more air bleed area to the idle system, but will also have a secondary effect on the main system since it controls the amount of fuel to the transfer slots.

    That system was standard on Pontiac carburetors, and sparingly used on a few other units.

    In and after 1970 it will lead to drilled passages above the main air bleeds and was used on Pontiac carburetors from 1970 thru 1974. For these models it has no impact whatsoever on the idle system since it introduces more bleed area to the primary main fuel instead......Cliff
     
  11. TORQUED455

    TORQUED455 Well-Known Member

    So getting back to the original question, early QJ’s didn’t have APT?
     
  12. Jim Weise

    Jim Weise 1000+HP

    No, not the type your thinking about, located in the bowl... until about 75... They had a non-adjustable screw with a stop for the power piston, under a cover in the baseplate that started about 68'ish... Cliff does sell a screw to make the early carbs adjustable externally.

    JW
     
  13. TORQUED455

    TORQUED455 Well-Known Member

    That particular one you are referring to is more of an “up-stop”. I’m surprised the carb I’m working on doesn’t have the one in the baseplate that likes to seize-up.
     
  14. Jim Weise

    Jim Weise 1000+HP

    Yes, and with the addition of tapered metering rods, you can in fact adjust your cruising A/F mixture externally, by altering how far down the rods are, on the stop. Works pretty slick, used it on the dyno before, for adjusting part throttle A/F mixture. Range is somewhat limited, you have to be in the ballpark to begin with.. fine tuning aid.
     

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