Can anyone tell me the history of the 351M? I am told it was a big-block? is that true? Also, what years was it used and what are the horsepower/ torque ratings on it. BTW, the particular 351M I am talking about came factory in a '79 F150 4X4, indy pace car edition, still running at about 265,000 miles.

Crotteau

 

It is not a big block. It is a 400 Cleveland block, with a 351 Windsor crank. The 400 block is the same as the 351C block, except the cylinders are an inch taller. Technically it's bigger, but it is not a big block. It was only produced because the demand for a 351 at the time was more than the Windsor plant could handle, and because the Cleveland plant was still producing 400's. it is nothing to write home about, and is often considered one of Ford's weakest engines. The parts available for it are very limited as well. Average hp was 145-155, and it went into production in either 1974 or 1975.

Take care,
-Chris

 

Not arguing here but I thought the Windsor was a small block and the Clevland was a big block.

I do know some call the 400s "351 modified 400"

 

i believe both were small blocks . even tho the 351 is taller then other ford small blocks it is far from a big block .

 

Yes you are right. The Cleveland engines are a family of big blocks and the Windsor engines are a family of small blocks. I do know that for sure. And the M in 351M does stand for modified.

 

I guess it depends on who you're talking to. I have never heard anyone refer to Clevelands as big blocks. Their dimensions are much closer to the Windsor small blocks than to anything else, but hey, it's a free country, call it a super duper block, if you like.

As far as the M designation meaning Modified, that is correct, but it doesn't mean performance. After production ended on the 351 Cleveland, apparently the Windsor plant was unable to keep up with customer demand for an engine of this displacement, so the Ford engineers "modified" the 400 by installing the 351W crank in the 400 block.

Take care,
-Chris

 

A couple years ago, just before I did my engine swap I was doing a lot of research on alternate engine choices. I came across a very detailed web site about the Clevor engines, you know, 351W block, 351C heads. The site also included a very comprehensive history on both the Cleveland family and the Windsor family, bringing to light all the high points and short comings of each engine. The Windsor is believed to be the better block due to its cooling superiority over the Cleveland, while the Cleveland's heads are eons better than the Windsor heads, thus, the Clevor engine is the best of both worlds. Somewhere amidst the wealth of information I can vaguely remember now, were the classifications of each engine family, and one of the few bits of information I vividly remember was that the Cleveland was actually a big block, while the Windsor was actally a small block. You see, the 351W is the largest of its respective family, while the 351C is the smallest of its respective family. The irony has stuck out in my mind for over 2 years now.

 

That is really interesting, and I understand your reasoning. Really. But every book and manual I own, and every parts house I deal with, all refer to the Clevelands as small blocks. The BOSS 302 was a Windsor block with Cleveland heads. That may have something to do with them being referred to as small blocks, since the Cleveland heads just bolted onto the Windsor block. I dunno. It really doesn't matter. I just didn't want anyone to look foolish walking into a parts store and asking for parts for their 351 Cleveland big block. Now, there was a 352 big block, but that's a whole other story.



Take care,
-Chris

 

--The Ford 351M and 400 cubic inch V8 engines are members of the Cleveland, or 335 series family of Ford engines, Small blocks.
--Ford Engineers developed the 400 engine in response to the new Government pollutions requirements that were to start in the 1971 model year.
--So, Ford chose to develop a new engine based on the new, super powerhouse 351 Cleveland. Just barely a little over a year old in 1971, the 351C had already gained the reputation as one of the best Ford engines ever built. The 351C was able to produce very good low-end torque and yet it could pump out earth shattering horsepower all the way to 6,500 RPM. The 351C was light, powerful, extremely rugged, and got better gas mileage than most other engines 2/3 it’s size. This was just what the doctor ordered!
--The engineers at Ford took the basic 351C block and modified it to power a whole new generation of environmentally-friendly cars and trucks. To start, Ford changed the transmission bell-housing pattern to match that of the larger 429/460 engines. This would allow Ford to continue putting the larger, heavy-duty 460 C6 transmissions with the new 400 engines. Ford also enlarged the main journal diameter from 2.75 inches to 3.0 inches allowing for a greater bearing wear area. The crankshaft stroke was also increased from 3.5 inches to 4.0 inches for a 50 cubic inch increase in engine displacement and greater low-end torque. Finally, the deck height was increased 1.09 inches in order to accommodate the 400s larger stroke. Consequently, the intake manifold had to be widened approximately one inch to accommodate the new deck height. The rest of the engine remained virtually the same. In fact all of the 351C valve train components (except for the pushrods) interchange with 351M/ 400 engines. The 351M/400 cylinder heads will also interchange with the 351C 2brl heads, although the 351M/400 heads have 78.4cc combustions chamber where as the 351C 2V heads had a 76.2cc combustions chamber.
--The “M”, by the way, does not stand for anything. Ford only used the “M” designation to distinguish it from the 351 W (Windsor) and the now discontinued 351C (Cleveland). The “M” designation has now mistakenly become know to mean “modified” or “Michigan”, even though the 351M was produced at both the Cleveland foundry and Michigan casting center. A good mechanic knows the true designation.
--To develop the 351M, Ford simply shortened the “throw” of the 400’s crankshaft to the original 3.5 inches used in the 351C. The larger 3.0 inch journal diameter of the 400 was retained in the 351M. To accommodate the shorter stroke, the compression height of the 400’s pistons had to be enlarged to raise the compression ratio up to 8.0:1. So, other than the crankshaft and pistons, the 351M is exactly the same as the 400. Even the connecting rods interchange.
--The year 1977 brought another set of changes to the 351M/400 engines. A new bread of trucks were about to hit the market: The new full-size Bronco. Ford decided to continue to use the 351M as the standard engine in the F-150, 250, and 350 4x4 trucks and to use it as the standard engine in the new Bronco. Ford also decided to use the 400 as an option in both the F-Series 4x4s and Bronco as well. In fact, if you own a 1977 ½ to 1979 Bronco, then you have either a 351M or a 400, as no other engines were available in these trucks! Both the 351M and the 400 received a larger ½ inch wide 5 link timing chain and sprocket. Along with some other minor changes, this led to the 351/400 “truck” engine.
--1979 was the last year the 351M/400 engines were produced in large numbers. With the continuing effects of the OPEC oil embargo and the ever-increasing pollution and gas mileage restrictions coming out of Washington, Ford decided to to use the I-6, 302, and 351W engines in the new line of light-duty trucks Ford was developing for the 1980 model year. This meant that end of the 351M/400 engine was finally carved in stone because Ford decided to phase out the production of 351M/400. Oddly enough, Ford continued to install the 351M in some early 80s model Broncos and both the 351M/400 in some of the F-250 and F-350 trucks until the last one was used in 1982.

 

I don't consider any Ford 351 or 400 to be a "big" block. The 352/360/390/428 was a "big" block as was the short-lived 427 and the 429/460.

 

My 2 cents, the term "big block" is usually used for the 370/429/460 and "small block" is what we call the 260/289/302/351.

That said, the 351/400 is a big block. I have had one on a stand in my garage for nearly a year, and it's noticeably wider and taller than the 302 that's sitting next to it.

It's also nearly the same size as my 460. The intake manifold is actually wider, and heavier...

 

Welcome aboard Lwj, thanks for bringing a good ford history lesson back from a few years ago.

How ya like yer '77?

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