Need help with a buddies 351M, err 351, err I dunno

Discussion in 'Other Auto Tech' started by caseywan, Jun 18, 2007.

  1. He has to install some new part on his 1981 F-150 Custom, and first off we need to find out for sure whether the thing has a 351M or a 351C.

    Naturally you would think that it has a 351M because it's a 1981 and the 351C was retired in 1974. BUT.... before he bought it, it had a new or rebuilt motor installed. So I am wondering maybe if the previous owner installed a 351C instead because of the poor rep of the 351M.

    So... I don't know how to tell the difference by looking at the motors, they both look the same. Maybe you can't tell the difference without looking at casting numbers, I dunno. :shrug: Anybody know how to tell the difference??

    Secondly, he wants to put on an aftermarket intake manifold and carb. If it is a 351M, will an aftermarket intake and carb for a 351C work or does it have to be specifically for a 351M (if there is such a thing)?

    Any help would be awesome!
  2. 351M(modified) is a modified 351C, any 351C parts should bolt up to an M
  3. The 351M has a 1 inch taller deck than the 351C hence I dont think a Cleveland intake would fit on a 351M.
    It would be like trying to put a 351W intake on a 302.

    The 351M is a destroked 400 engine.
    The 400 engine is based on the 351C design but with taller decks and different internal dimensions; not many parts interchange.
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