800cfm spread bore thermoquad compatibility?

Mopar Performance Issues

  1. LovetheA's

    LovetheA's FABO Gold Member FABO Gold Member

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    I scored an older 800cfm aftermarket thermoquad spreadbore manual trans carb. I want to put it on my 383 with new Eddie heads and Eddie rpm performer intake. Do I need an adapter spacer to fit on the manifold?
     
  2. rumblefish360

    rumblefish360 So close, yet so far away FABO Gold Member

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    Yes. Unless you put down the gasket and there is enough meat of the intake carb mounting pad to carve up with the die grinder to take that route.... if you wish to do so.
    But I don’t think so.

    I know you just scored the carb but I figured I say you’ll be better off and much more happy with the large primary TQ. Been there done that on a B 400.
     
  3. Bewy

    Bewy Well-Known Member

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    Try to avoid an adapter at all cost. The RPM has the dual bolt pattern, so the TQ will physically bolt on, but the t/blades might hit the manifold. You can probably grind the carb mounting pad enough to fit the TQ. You may find that you will get an air leak
     
  4. Bewy

    Bewy Well-Known Member

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    from the passages in the carb base. In this case, you can Devcon or JB weld the passages closed for leak free operation. I have done this many times, never a problem.
    Agree, the 850 cfm might be better, but the difference will be very slight & may not be noticeable. 454 Chevs, 455 Buicks, Olds, Pont all came with QJs that are the same size of the 800 TQ.
     
  5. rumblefish360

    rumblefish360 So close, yet so far away FABO Gold Member

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    @Bewy My mention of the larger one is strictly from a drivers stand point and not at wot. In my particular case I opted for the smaller primary TQ since it had the electric choke.
     
    • Agree Agree x 1
    • LovetheA's

      LovetheA's FABO Gold Member FABO Gold Member

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      Okay thanks everyone for the heads up.
       
    • 340fourspeedDuster

      340fourspeedDuster Well-Known Member

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      For a 383 engine, either carb size will work fine. The secondary butterflies are the same size on both the 800 and 850. Secondaries are 2.25" diameter. The primaries are slightly smaller on the 800. This works well for off throttle response. Your vehicle, your choice. If you have the 2186 Edelbrock Performer manifold, it is designed for a spread bore carb. The RPM is for a square bore carb.

      Screen Shot 2021-04-10 at 4.53.41 PM.png
       
      Last edited: Apr 10, 2021
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