I own an '86 f250 w/ the 351w. I love it, it's a great little engine. So what's the difference between it and the cleveland or the M (I assume that stands for Michigan?) I know this seems like dumb question, but I'd be even dumber if I went on not knowing the differece. Thanks folks.

 

Please read the "sticky" Forum Guidelines at the top of the page. We won't be discussing what "M" stands for or whether or not the 351M/400 is a "big block" or "small block" in this forum.

The difference between the 351M and the 351W is that they were derived from 2 different engine families. The 351W is related to the 289/302, the 351M is related to the 351C. The major difference is in the heads. The W heads have "straight up" valve orientation which limits the size of the valve heads you can fit in the combustion chamber. The 351C (and M) heads have a canted valve design which means that the valve heads can be much larger in the same bore size and therefore the airflow is increased. Overall the design of the C/M heads is much more performance oriented than the 351W.

 

Thread has been reopened.

If anyone else would like to add to the description of the differences between the 351W and 351M feel free to do so but please keep in mind the guidelines.

 

so are parts for the 351m or 351c interchangable with each other? With the Windsor? Can the heads be interchanged? I read that sinch the C/M is a lower reving engine, but produces more torque. Wounldn't this make a better engine for a heavy ol' truck?

 

Many parts on the 351M and 351C will interchange. Heads, cams, valvetrain, timing components, distributor & oilpan off the top of my head. The W and C/M heads can be interchanged with some minor modifications as well.

The C was actually designed as a performance engine, the 4V head design was patterned from the Boss 302 which Ford produced in 1969 to race the Trans Am circuit. It was never installed in F-series trucks.

The 351M has a larger crank and longer rods than the 351C and because of the taller deck height of the block it has taller, heavier pistons which, in addition to other factors, limit the RPMs the engine is capable of turning. It was built in 1975 as a replacement for the 351C and was only installed in large sedans initially. In 1977 it, along with th 400 replaced the 360/390 engines in F-series trucks. It was designed from the factory as a smog motor and never had any factory performance parts built. It never even came stock with a 4 bbl carb.

The 351M, W and C all share the same bore & stroke (4.0" X 3.5") but they all have different blocks so the main difference is in the crank, rod & pistons. Is a 351M a better truck engine than a 351W or a 351C? No idea, I guess it all depends on what you use your truck for.

 

Check this page for some more background info on the 351M/400 engines. The second page has a table that lists the main components that interchange betwen the 351M/400 and 351C.

http://home.earthlink.net/~bubbaf250...history01.html

 

The 351C builds 200 more horsepower than the M, the W builds 100 more than the M.

The M is not a performance motor, and is a sad way to describe Ford. It doesn't even build that much torque, the W is a true truck motor. The aftermarket support for it is astronomical, and it is a very dependable motor.

Whether or not any of that is my opinion I have yet to determine.