Howdy,
I have to switch to a 351C from a 351M in a '79 F-150 (long story). How hard will that be? I am not talking about work hard, I am talking about "fitting"?

Thanks,

Buddy

 

Have to change engine mounts and the transmission bellhousing if it's a manual trans, have to change to a small block bellhousing pattern trans if it's an auto. (Whole trans.)

 

I thought the 351c and 351m have the same bellhousing bolt pattern not sure about the motor mounts.

 

Since the 351C is somewhat smaller than the 351M/400 and the 460 (all of which were available from the factory in '77-'78 F150s), it will "fit."

The 351C has the same "small block" bell housing bolt pattern as the 302 and 351W.

The 351M/400 has the same "big block" bell housing bolt pattern as the 429/460.

The 351C uses the same motor mounts as the 302 and 351W. The 351M/400 uses a unique motor mount.

As pat67shorty said, you'll need to change the bell housing for a manual transmission, or change the whole transmission if it's a C6 (which has an integral bell housing).

BTW: For guys with car trannies, the FMX and C4 have separate bell housings, available with both (big and small) bolt patterns.

 

Another area of concern might be the exhaust and intake manifolds, which would depend on the year/variant of the 351-C you're swapping. If you have a stock 351-C 4bbl carb and manifold setup, the 351-M exhaust manifolds will not fit. If your 351-C does not have an intake manifold, the 351-M manifold is not compatible.

I'm also not sure about the year of your vehicle and its front suspension, but on mine, the oil drain plug sits in a really bad spot over the front axles. When I first drained it, oil everywhere! So when you get it in, check out where the drain plug exits; you may need to use one of those "drain plugs made easy" or whatever they're called, that will allow you to direct the drainage to your receptacle.