351 M/c/w
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New User
Joined: Aug 2006
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351 M/c/w
Hey all, this may seem like a stupid question to the more educated and experienced of you. But could anyone tell me what is the difference between the 351 Windsor/Cleveland/Modified??? And which one is best... Just curious. My truck has a 351W but my girlfriends old truck has a 351M in real good shape, i was thinkin stealin it and putting it in mine...
Post Fiend
Joined: Apr 2006
Posts: 12,281
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From: Saskatoon Saskatchewan
Well iam not 100% sure on this someone correct me if im wrong but i think they where made in different years with different designs and i think made in different plants the like 351C was made in early 70's trucks and in a lot of cars then late 70s early 80's the 351M came in it was a destroked 400 then lated 80s to mid 90's the 351W came in im not sure which one is exactly the best
Senior User
Joined: Nov 2005
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From: Collierville
The 351W is a Windsor engine - basically the largest small block Ford made. Very similar to a 302 or 5.0 etc. The 351C is a cleveland engine. It was essentally a high po car engine and you won't find any stock in a truck. It should however fit in the same application as a M engine. The 351 M is for Modified. It is actually a 400 big block that was destroked. It was essentally designed for trucks and has a taller heaver block and can produce lots of touque.
You would probably find it cheeper and easier to just rebuild the existing engine. You can make a pretty good engine out of a 351W for not too much money.
You would probably find it cheeper and easier to just rebuild the existing engine. You can make a pretty good engine out of a 351W for not too much money.
Lead Driver
Joined: Feb 2003
Posts: 8,140
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From: Oak Harbor, OH
Okay, the 255/289/302/351w are all WINDSOR motors, built in Windsor Ontario, Canada. The 351C/351M/400 were all built in the cleveland plant in cleveland ohio. The 400 was a modified 351C (designs are very similar), the 351M (modified) was destroked 400. There aren't a lot of parts that will interchange between the 351C and the 400/351M but they do share a similar design.
Postmaster
Joined: Aug 2004
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From: West Mansfield, Ohio
If you go to the 335 series engine forum you will see the difference. It's actually unknown what the "M" stands for after the 351. The C is Cleveland of course, the W is Windsor, and Ford has yet to release documented information on what the "M" stands for. And by the way, Ford's don't have "small blocks" or "big blocks." Those are words to describe Chebby engines. We have the 335 series (351M, 400, and 351C,) made in Cleveland. Then there was the 289,260,221,302 and 351W all in one "family." Commonly called the "Windsor" family. Then there was the 385 series, with the 370 truck engine, 429, and the 460, which were all made in Lima, Ohio.
There is talk that with "M" falling right in the middle of "C" and "W" in the alphabet, and the 351M sharing componets from both, that this could explain the "M". There is also talk that it could stand for Michigan. There is also talk that it could be "modified." Please note that this WAS the 70's and there were probably some illegal drugs mixed in with this somewhere haha.
But nevertheless, nobody knows for sure what the M stands for. If you go to the 335 forum you might find some stuff. For God's sake dont start a post asking what the difference is. They frown upon that. Read the "read firsts" at the top of the forum page first.
There is talk that with "M" falling right in the middle of "C" and "W" in the alphabet, and the 351M sharing componets from both, that this could explain the "M". There is also talk that it could stand for Michigan. There is also talk that it could be "modified." Please note that this WAS the 70's and there were probably some illegal drugs mixed in with this somewhere haha.
But nevertheless, nobody knows for sure what the M stands for. If you go to the 335 forum you might find some stuff. For God's sake dont start a post asking what the difference is. They frown upon that. Read the "read firsts" at the top of the forum page first.
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Well all i know is that the windsor in it right now runs like crap and has dropped 3qts of oil in less than a week and the 351m runs like a champ. Are they interchangeable? My truck is an 83 f-250 with a 351W out of a 78 E-250, and the 351M is in a 78 F-150.
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Lead Driver
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From: Kalispell, MT
Anything is possible with enough work. Keep the tranny with it's original engine - bellhousings are different between W and M. You'll need to find motormounts.
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Freshman User
Joined: Jan 2006
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From: Tonawanda, NY
My truck has a swapped in 351M replacing the Windsor and i LOVE it. Its not a good high RPM engine though. If you swap it make sure you find a "big block" bell housing. the 335s use the same bell housings as the 385s
I'll have the Roast Duck
Joined: Jul 2002
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From: Northshore, MN
I used a 79 400(same as 351M) put into my 83 f250. As long as they are either both 4x4, or 2wd, they will drop right in, no need for new motor mounts. if it's a 4x4 engine going into a 2wd frame, you'll need new motor mounts(and oil pan). Anyway, the bellhousing bolt pattern will have to match, like Mtflat said. If you drop the 351M in, you'll need an 82 F250 mechanical fuel pump(w/inverted line from frame). If you want headers, you'll need to go with a hydraulic clutch, or an automatic. The manifolds(not headers) are engine specific, but the 78's will work in the 83, you'll need an 82 F250 crossover pipe. You'll also need an 82 351M radiator. I'd opt to use the duraspark II if you don't have it already. But, in the long run, if it's HP you want, rebuilding the 351W may be the best option dollar to dollar. But if you want stump pulling torque, then the 351M will work well. Eventually if this is the route you go, the 335 series forum can direct you to build that 351M into a high power/high torque 400. Good luck.
