I have a Question can i simply put a 351m crankshaft int a 351w engine block or would I have to make modifications to it. I see that the 351m and 351w crank have the same mains, stroke and rods. If i could put the 351m crank into 351w what would i have then?

 

you would have a motor that doesnt work. those are 2 different engine families. you will gain nothing.

 

They are the same stroke, so even if it works, you gain nothing.

There are lots of aftermarket stroker cranks and kits for the 351W.

Scat Ford Stroker Kits 351W to 408 from RPM Machines.

 

Thanks for the info.

 

the modified cranks are just a copy of the cleavland cranks.. the 400 has a longer stroke but i still doubt the journals will even line up

 

I though though the 351m had a windsor crank in the block. It just has bigger counter weights on it?

 

oh wait, you're right.. it's cleavland top end.. lol sorry..

 

The 351M shares the main journal spacing of the 351W and the journal sizes as you stated. It will bolt right in to a bare block, but I believe there is a difference in the snout which means it either has to be modified (machined) or you would have to use the 351M balancer etc. and the pulley might not end up in the wrong location fore and aft.
Before the advent of readily available stroker crankshafts, 400 cranks used to be modified to fit the 351W and the front snout was remachined to suit the 351W balancer.

The counterweights probably are larger on the M engine than on the W engine since the con rods and pistons are heavier on the M engine. If this is so, then while the M crank could be made to work, it will require a lot of machine work.

 

yeah, the snout is definitely larger on the 400M cranks