I'm just curious about these engines, as I might be acquiring one in a project truck and I was wondering what the differences are between a 351M, 351C, and 351W. I know the later ones are Windsors. Why were the Modifieds and Clevelands discontinued? I believe I might know a few differences, but I thought I might ask, so I could "stand informed" on the differences. Thanks.

 

Well, to start off, the 'C' stands for "Can you believe they only built 351'C'levelands for for 5 model years?........'M' stands for, 'M'Y God, there are not very many parts available......And 'W' stands for...... 'W'ould you believe they focused on a head design that is too wimpy for even a 289?
351 C...Built at the Cleveland engine plant, canted valve heads, bulletproof crank, bad stock oiling system, 4v heads have the largest ports of any factory small block, and valve sizes the same as a rectangle port 454 head, 2v heads, still some hefty valve sizes, make really good power if built right
351 M/400... the 400 came first, was designed as a low rpm torque motor, has more stroke than a 460, long rods for a good rod ratio, same engine design, but has taller deck height than a 351c, and not too many performance parts available, although alot of the 351 parts bolt on and in, and then when a smaller engine was needed for full size cars, the went with a shorter stroke crank, and voila', the 'Modified' 351(Note, if your engine is a modified, you will get laughed at and called silly names if you don't put a 400 crank and pistons in it, it runs that much better)
351w...completely different than the 351c, although they share the same bore and stroke, same bore spacing, etc. the 351W was produced at the windsor, ontario engine plant.....The 351w is essentially a way oversized 289/302 with the same crummy heads as the 302/289 units, which are too small for those motors as well, but they have a really god oiling system, and there are a ton of aftermarket parts for it, including several pricey head options.........Shazam, how did I do???

 

Ok, so that's why the Windsors only had 210 ponies. I was interested, because I saw a replica Cobra on the tv with a Cleveland. I like the power the Cleveland is capable of producing. I always wondered why the Windsors were so underpowered. Thanks for the info. Also, what years were the C's and the M's made? I believe I read the W's were from 1969-98? I might have a few more questions later on as they come to me.

 

'C's were built in the US from model year 1970 to 1974(?), and 400s from 70-71(?) to around '78(?), and 351m's from around 75 to 81-82.

keep in mind, that you are kind of limited to what you can do with the 351c, you can only modify it so far before it starts becoming more of a hi-rpm screamer, and useless for heavy truck useage. The 400 is the best to use(you can add 400 pistons and a 400 crank really easy) for heavy trucks, the 2 I built pulled like turbines from idle to 5000 rpm, and with wimpy cams......
If I remember why the 351C,M,and 400 were canceled was due to space limitations in vehicles, and Ford wanted to keep the engines (I can't think of the word, maybe platform.....) the same basic design, and the 351m and 400 were oddballs, and treated like red-headed stepchildren.
anyway that is a general idea of who and why about the 351c,M, and 400.......

 

Don't buy the bad press from another board. The 351W has a lot of potential. There is another ford-truck board for the 221-351 Windsors.

 

Thats why I went to building a clevor. Using a 351 windsor block but using 351 cleavland 4v heads. The only regret after soaking a fortune into this motor is that I didn't build a stroker. That will come though. I am buying a hilborn eight throttle body multiport injection system for it this year. Call me crazy but Its awsome. Bob

 

Sorry, I was not trying to be the Spreader of Bad Press, but the only engines I have been working on and building for the last 9 years are 289-302-351w-393w-427w strokers, the Cleveland equipment has been only sporadic since the late 80's-early 90's, where my primary focus was. And yes, the windsors have a lot of potential, but you have to spend money on the heads first and foremost to get any power out of them, and none of the stock pieces really work very well, even the vaunted 69-71 351 windsor head; they sound great on paper, but anyone try to port the exhaust ports on one of those? ( a notable exception would be the GT40P). The exhaust side of all of the typical windsor heads are bad to work with, and that is after years of trying to port them out, only to bolt on an out of the box aftermarket head(good example, the AFR185), and only then does the engine wake up and run. Hey, Sorry about mentioning anything windsorish here........

 

lvmoose007
You did a very good job at telling the differantes of the 351w, 351c, 351m/400..
Just remember Ford never really made a bad Motor. Just some misunderstood motors, that with some TLC become kickbutt engines.

 

I believe the 400s and 351Ms were phased out at the same time, 1982 and Ford decided to go with the 460 as the only large displacement truck engine.

Also I'm with bubba on the reasons for the demise of the 351M/400. It's the only engine which wasn't easily adaptable to a computer controlled EFI setup because the thermactor ports are in the heads instead of the exhaust manifolds so it's difficult to get an EGO reading "upstream" of the air injection ports . Even the late model Clevelands had thermactor ports cast into the heads.

 

Thanks, Bill, as soon as I heard the word EFI, I realized that I forgot a few things( that's why '?'s were all over the place, lol). No, I don't think that any of those motors were junk, just alot of potential gone to waste thanks to Ford. I think the 351m/400 is the better of the two(351c, 351m/400) engine designs, and I think it was a good idea to kill off the 351c. Reasons? for starters, even at the same stroke, the 351m has a lot more potential than the 351c, due to more stroke potential, the capabilities for up to a 7.0 inch rod, which would allow for a heck of a lot compression, even on pump gas, and I think that the 351m/400(after having both 351c's and 351m/400's apart and rebuilt) is a stronger block. Want an example, Shazam has two. Yes, they are extreme examples, but Shazam did this with stock heads( hey, try a yates sometime, and post the results.....). Try getting that out of a 351c with out blowing the block apart, or having something so light switch of a power delivery that it would be completely undriveable on the street. I don't hate the 351c, I just think it was good first experiment before the 400. I have even thought about building a hi-rpm runner out of a 351m, with the longest rod inhumanly possible, closed chamber 4v heads with the port floors filled in, and why not a tunnel ram on top, should make decent power, about a 100 more hp than a similar equipped cleveland(by what I am looking at, others will have different ideas)...........just my $.02

 

Just as an FYI thing, the thermactor setup DOES NOT affect the O2s readings. The 300-6 has AIR injection into the head, as do many other engines from many other manufacturers. The upstream injection only takes place when the engine is cold, in open loop, and the O2s is being ignored. The real reason that the 351m/400 was dumped was that by the time 82 rolled around, and Ford was still in their "Drop the compression" phase, these motors had been so choked and castrated by emissions crap that they couldn't take any more. If they had been left at 8.5+ compression, they would still be the mainstay of the Ford truck line, IMO.

 

That would explain a few things.....and I also heard that the 400's were dropped due to space limitation reasons, I have had ideas for a few years now to install a 400 or 460 into a late-80's crown vic wagon, and for all of the size of the hood, there really is not much room under there for anything much larger than a 302 without bumping into something else. The SIX explanation sounds great, it is hard to continually detune an engine with huge intake and exhaust ports, that is easily done with the tiny heads of the windsor line. Hey, now I am rambling.....

 

Which was better for making power?

 

Welcome to FTE. This is a 12 year old thread. A simple search can tell you more than you ever wanted to know.

As OEM:

351M--hopeless
351C--good to red hot
35W--pathetic to pretty good

With aftermarket performance parts:

351M--na, remains hopeless. Good basis for making a 400, which can be built hot.
351C--Redder and hotter if you like
351W--red hot, including aftermarket blocks for 427 CID. Probably the least expensive of the three to work on in this way.