71 vs 72 thermoquad

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  1. Demonizer71

    Demonizer71 Well-Known Member

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    What's the Difference? Plus will a 72 work on a 71 intake? I've read that the 71 Tquad had smaller primaries for emissions etc.
     
  2. 2 Darts

    2 Darts A-body Addicted

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    The only difference between the two that I'm aware of is that the 72 has EGR and ported-spark vacuum connections. Later models had electric chokes, but I'm not sure when they were introduced on production Mopars. Venturi size on early and late models is the same. There's no reason why a 72 carb would not work on a 71 manifold as long as the un-used emission ports were properly capped.
     
  3. george

    george Well-Known Member

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    I think this needs clarification. The large/small primaries were not year specific. They made both sizes pretty much throughout the '70s/early 80s.
     
  4. perfacar

    perfacar Well-Known Member

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    hi, the carbs will work as both use same intake manifold. the difference is in the secondary jet. the 71 sec jets were shorter as the body had longer casting to put jet near the floor. the72 and up, has a longer sec jet, commanly refered to as a solid fuel type.the casting was shortened to make then fit. both have 1 3/8 primary throttle bores. the 340 used the 1 3/8 bores. 71 through 73 . the intake 2100 has no EGR fittings in floor.
     
  5. yellowdartdave

    yellowdartdave RIP 1-5-12 Legendary Member

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    And they all come with that beautiful full throttle wail !
     
  6. GTXperience

    GTXperience Orig Stealth Mod

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    Air-metering vs fuel-metering. A lot of people like to go with the '72 & up for this reason.
     
  7. 70aarcuda

    70aarcuda Master Hoader of SBM FABO Gold Member

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    that is the big difference....agree...alot of people use the 72 and newer air metering thermoquad.

    unless you are doing a restoration...i would use the 72+....

    last weekend at MATS, a friend has a 71 demon D/SA that was running a 72 and newer thermoquad...
     
  8. rumblefish360

    rumblefish360 So close, yet so far away FABO Gold Member

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    72 and newer carbs are solid feul metered.
    The earlier carbs have press in jets.

    Get the scoop by a pro; http://thermoquads.com/
     
  9. 71duster06

    71duster06 Well-Known Member

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    72s are 850...the 71 was a 800 cfm...also the 71 was harder to get to run right...go with the 72
     
  10. demon sizzler

    demon sizzler Well-Known Member

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    Just to 'clarify' a few facts on the subject. The differences are:

    The '71 340 carb was 'based' on the Competition Series 850 cfm T.Q. and
    as stated above, the '71 T.Q. was:
    a)air metered..................'72 model was fuel metered;
    b)both the '71 340 and the '72 340 carb was rated @800 cfm's;
    c)'71 jets, bowl, base and top are NOT interchangeable with the '72 carb/parts;
    d)'71 340 had the idle mix screws 'angled' away from the centerline of the carb while the '72-'84 oem carbs had the idle mix screws 'angling' upward;
    e)the '71 340 carb had the front vent stack as an integral part of the top casting while the '72 carb had a push-in cylindrical steel vent stack;
    These are the most noticeable side-by-side differences between the two carbs. An the '71 carbs are worth more $$$ because of the 'rarity' of the '71 model.

    The '72 is the better performer of the two because it has more sophisticated metering systems. The '71 carb is easier to pull trash into the metering system while the '72 has the cronic problem of leaky main jet wells on the underside of the bowl.

    In my opinion, the '72 340 carb is the best performing 800 cfm T.Q., David

    '71 340 T.Q. pic:

    DSCN1531.JPG
     
  11. MopaR&D

    MopaR&D Nerd Member

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    What is the difference between air and fuel metering, as in how do they work?
     
  12. 6T9 V-100

    6T9 V-100 Well-Known Member

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    Hey Demon Sizzler...got a TQ off a '72 D250 w/ a 360 under the hood. Truck had about 70k on the odo, was in a wreck that wiped out the driver's side. Picked up the carb for $30 and was planning on using it on my budget-built 340. Can I pick your brain on this thread (don't want to high-jack) and spread abit 'o knowledge-I know you are the TQ guru.
     
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