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Technical The great C4 debate

Discussion in 'The Hokey Ass Message Board' started by topher5150, May 22, 2020.

  1. topher5150
    Joined: Feb 10, 2017
    Posts: 1,783


    If this has already been addressed by the great and powerful Ford gods then kindly point me in the right direction. If not I humbly present to the benevolent Ford gods a sacrifice of my first born.
    In my 47 Ford coupe I am putting in a 351W from an 80s truck. The transmission is from a 71-72 302 Mustang (PEE AC4 D 27PDAJ25). I have determined that the transmission is a 157 tooth bellhousing (5.875" BH depth, and 10.50" T/C)
    What I need to know is can I use a 157 tooth flexplate on a 351W? Can I retain the 351W's current harmonic balancer? Or do I have to get a new bellhousing/torque converter?
    Thor1 likes this.
  2. No issues... All 289/302 used the 28oz balance until the early '80s, and the 351W did all along until the end of production. It only gets weird when you try mixing 28 and 50oz stuff. A C4 to a 50oz motor, you need a aftermarket flexplate. AOD to a 28oz motor, same story. In this case, if you have all the matching OEM parts for that trans it's a bolt-on.
    RICH B, loudbang and Thor1 like this.
  3. One last comment. Ford didn't factory install the C4 behind the 351 because they didn't feel it could take the torque and meet their reliability standards. OK, there was some exceptions; some of the last of the car-use 351s starting in the late '70s used the C4, but by this time the power was smogged down to 302 levels. You might consider 'freshening' the C4 with some upgraded bits for the increased torque, particularly if you lean on the motor.
    loudbang likes this.
  4. topher5150
    Joined: Feb 10, 2017
    Posts: 1,783


    Ok that wasn't as painful as I thought it was going to be.
    Sent from my moto z4 using The H.A.M.B. mobile app
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  5. doyoulikesleds
    Joined: Jul 12, 2014
    Posts: 247


    the 351 went to 50 oz in 84 or so so you need to know what 351 you have
  6. Nope, it didn't. The reason for the change on the 302 was because they seriously lightened the crankshaft and needed the extra external weight to offset the lighter crank counter weights. The 351W used the same crank all the way through.
    topher5150 likes this.
  7. BamaMav
    Joined: Jun 19, 2011
    Posts: 3,991

    from Berry, AL

    I had one of those exceptions---1978 Granada 351W C4. Had the deep bell like the C5 lock up converters with the large converter bolt pattern, same as the AOD. Definitely not a performance engine, 2 barrel, but torquey. I used the engine in a 4x4 pickup, it did fine, trans was later used behind a late model 5.0 flat tappet engine with an AOD flexplate.

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