Tech

What’s the Difference Between a Ford 351 Windsor, Cleveland, or Modified Engine?

Ford-351-Windsor-on-Dyno

There is plenty of aftermarket support for Ford 351 engines, the tough part is figuring out which engine you’ve got. (Image/Hot Rod Network)

Engines are often identified by their displacement, like the ubiquitous Chevy 350, Mopar 440, or Ford Five-Oh.

But displacement alone isn’t always the best differentiator, and nowhere is that more evident than with the Ford 351 engines.

Sure, ‘351’ refers to the engine size, but there were essentially three major versions of the Ford 351—the Windsor, Cleveland, and Modified*.

*Officially, Ford never called these engines 400/351 Modified or 400M/351M. “Modified” was a slang designation originally applied by Ford enthusiasts, and the name just stuck. You’ll also hear folks define the “M” as “Michigan” after the engine’s original casting plant. The etymology doesn’t really matter, it’s just a way for us to distinguish it from the other 351 engines.

What version you have is very important to know, because major parts from each engine are not interchangeable.

To clear up any confusion, and to help you avoid buying the wrong parts, here’s a quick rundown on each motor so you can know for sure what you’ve got in your garage.

(Summit Racing‘s Tom Lynch contributed to this article.)

The Three 351s.

351 Windsor

Ford-351W

Ford 351 Windsor Engine (Image/Hemmings Motor News)

The 351W is named for the factory in Windsor, Ontario that produced them. It is part of the long-running Ford small block Windsor V8 family, which also includes the venerable Ford 302 (5.0L) V8. It shares the same small block V8 bellhousing pattern and motor mounts of the August 1964+ Windsor engines*. Key differences from the other Windsor engines include a taller deck height, unique firing order, and longer stroke.

*Pre-August 1964 engines (221/260/289) had a narrow 5-bolt bellhousing pattern, also referred to as the early V8 Windsor pattern. All post-August 1964 Windsor engines use a wider 6-bolt pattern (including all 351W), commonly referred to as the small block V8 pattern. The patterns are not interchangeable.

It’s far more common than the 351 Cleveland, and though it doesn’t have the “high performance” aura of its 351C counterpart, there is plenty of aftermarket support for it. Engine builders and hotrodders have no problems pulling gobs of horsepower out of these engines, and popular upgrades include cylinder heads, camshaft, headers, and intake manifold.

351 Cleveland

Ford 351_Cleveland

Ford 351 Cleveland Engine (Image/Wikipedia)

The 351C was built in Ford’s Cleveland, Ohio factory, and is part of the Ford 335 engine family. Back in the day, the 351C was considered the go-to Ford performance engine, thanks to its better-flowing cylinder heads and stronger crankshaft. Ford made both 2V and 4V cylinder head versions for the 351C, with the latter 4V heads being the more performance-oriented versions.

Unfortunately, Ford only produced the 351 Cleveland for five years (in the U.S. at least, Australia got the engine up until 1982). The engine’s rarity makes it a more expensive platform for an engine build, though it’s capable of making impressive power with the right upgrades. And, for what it’s worth, there’s still a ton of Blue Oval cache in saying you’ve got a real Cleveland under your hood.

351 Modified

351M-Engine-on-Dyno

351 Modified Engine (Image/YouTube – John Sivec)

The 351M is part of the same Ford 335 V8 engine series as the 351 Cleveland. It’s based off of the 400 Modified engine (see note on nomenclature in opening paragraph), which was essentially a 351C with a longer stroke. Unlike the 351C however, the 400 block had the bellhousing bolt pattern of 385-series big blocks. It also had a higher deck height to accommodate the longer stroke.

As the 351 Cleveland faded away, Ford engineers reverted to the original 351C’s 3.5-inch stroke, yet retained the 400’s deck height to create the 351M. The bellhousing bolt pattern on the 351M uses the same pattern as the 385-series big block engines as well.  (That means, even though they’re related, transmissions, intake manifolds, and other parts may not be interchangeable between a 351C and 351M.)

It’s also worth noting that the 351M was only available from the factory with a 2-barrel carburetor.

How can you tell the difference between the  351 engines by looking at them?

Three Easy Visual Differences Between the 351W and 351C/351M.

  • Radiator Hose. On a Cleveland/Modified engine, the radiator hose (and thermostat housing) sticks vertically right out of the top of the engine block. Windsor engines have the radiator hose and thermostat installed into the intake manifold, where it exits from the front of the engine.
  • Valve Covers. Windsor valve covers use 6-bolt covers, whereas the Cleveland/Modified uses 8-bolt covers.
  • Timing Chain. Cleveland/Modified engines have the timing chain recessed into the front of the block itself, and its timing cover is essentially just a flat piece of metal. The Windsor’s timing chain attaches to the front of the engine and has an external timing cover typically made of cast aluminum.

Three Easy Visual Differences Between the 351C and 351M

  • Cleveland engines share a bellhousing bolt pattern with the Windsor family. 351M engines use the bellhousing bolt pattern of the 385-series Ford big blocks.
  • Due to a higher deck, the 351M’s intake manifold is wider than a 351C.
  • Motor Mounts. 351 Cleveland mounts use two bolts to attach to the engine, whereas the Modified uses three.

If you’re not sure what bellhousing you have, check out this handy transmission I.D. chart.

Here’s a handy way to I.D. Ford Bellhousings. (Image/FORDification.com)

Why the Three Engines?

Though they share displacements, each motor was built and configured for different applications.

For instance, the 4V-351 Cleveland went in the top-tier performance cars, but the 2V351C engines could be found in a smattering of medium-to-full size 1970-74 passenger sedans too. By comparison, the 351M was used in 1975-82 passenger cars, light trucks, and SUVs.

(Ford engineers however, seemed to have stuffed a 351 Windsor in darn-near everything short of their coffee makers.)

And that’s what causes the confusion. Swaps between the three engines are common, so you can’t always match the engine to the vehicle you found it in. And, given the lack of interchangeability between key components, it’s absolutely critical to know what you’re wrenching on.

To put it into perspective, Ford offered the 351 Cleveland from 1970-74 (in the U.S.) and the 351 Modified from 1975-82. The 351 Windsor was available from 1969-97, making it by far the most common engine of the trio.

As a final historical footnote, the introduction of the overhead-cam Ford Modular V8 in 1991 meant that the Windsor, Cleveland, and Modified engines represent the final pushrod V8s designed by Ford.

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88 Comments

  1. The ‘M’ actually does stand for ‘Modified’. Reference the Ford Master Parts Catalog. Also a point of clarification, the M/400 also had a small bell pattern as well. I can provide pics of both as necessary.

    • Yes if you could I got an 80 f150 4×4 351 mod original engine but I never had a 351 m and not sure what I’m getting into rebuilding it

    • Years ago we called the 351M a “Michigan” or “Midland” because it was from the Midland Michigan plant.

    • Ben you are correct on both statements. And the 400 was not an M, just a 400 351 M was a modified 400

      • Just wondering is the 400 a big block or small people argue with me about all the time

        • Redneckgearhead says:

          Imo Ford never made a “big block” or “small block” that is a general motors designation. Ford had different series engines. But again my opinion.

        • The 335 series engines (C/M) share what’s known as the basic architecture, bore spacing, etc., with the Windsor family of engines, commonly known as the Small Block Ford. That would make the C/M engines technically ‘small blocks,’ albiet different ones from the W’s. They are not nearly as big as the FE engines or the 429/460’s. Interestingly, the old Y-block engines from 54-64 have the same bore spacing, too. The 260/289 was an updated replacement for the Y-block. The 335 series, with its design dating back to the mid 60’s, was originally intended to be the replacement for the 289/302, but government regulations and the oil embargo, mpg concerns, etc., in the early 70’s changed all that.

  2. Also worth noting…the W has 6 valve cover bolts, not 5.

  3. 351M/400 and 429, 460 all use the same bell housing.

  4. Daniel Wilson says:

    There are two more ways to visually identify a 351C engine in addition to those listed. The mechanical fuel pump located on the drivers side (U.S.) of the block near the front, is mounted with two vertically opposed fasteners. One on top and one on bottom. The 351W fuel pump is attached on each side horizontally, or left and right sides.

    I agree how confusing it can get, especially with so much misinformation online. It’s definate that all Cleveland production in the States of both 2-V and 4-V engines, ended in 1974. But I need to question a statement in this article that reads, “The 2V-351C engines could be found in a smattering of medium-to-full size 1975-79 Ford passenger sedans, and in 1977-88 light trucks too”. It could be a simple typo error or perhaps what I thought I learned over the past 40 years is totally wrong.

    Another point of identification that new fans of the 351C might not know is how to easily check for 2-V and 4-V (barrel) heads. In the upper most corners near the valve cover rails on U.S.production heads, look for the 2 or 4 indicator that’s cast into the head. There might also be a small dome shaped dot beside the number. It’s typically found on heads that were cast very late in the 1970 casting run and in the following years according to the casting date statistics. The dot indicates a minor change in production but it DOES NOT mean open or increased volume combustion chambers. My D1AE-GA closed or “quench” chamber 4-V heads, and countless more like mine have the 4* indicator. The 351M-400 heads don’t have number designations because they all have the smaller 2-V sized ports and valves with open combustion chambers. They do share the same basic Cleveland heads architecture and with a little work they will support substantially more horsepower over a wider rpm range than production Windsor heads.
    Boat anchors ??? The small block, double hump Bowtie variety from the General are perfect for that application. And the beat goes on…..

    • OnAllCylinders Staff says:

      Good insight–and yep, we confused ourselves on the 351M/C/W’s available years in the last section. It’s been updated–thanks for the heads up!

  5. rick wallace says:

    I got my first Ford in 1967, a 1957 del Rio station wagon , and have owned literly THOUSANDS more Fords since then. I have never seen or heard of a Cleveland in a pickup nor a 400 with a “FE” bolt pattern. I keep an open mind and learn something new every day but 3 other guys that bleed Ford blue when we bust a knuckle, agree. Besides those two items , your article I hope will educate all the “cool guys ” who always boastfull proclaim ” Its got a Cleveland” but can never tell me the differance between it and a windsor or modified. Thank you , good job setting the world straight,including the “down under boys”

    • Rick, I agree. I think more than one person wrote the original article and when someone said a Ford big block,(429/460), someone else was thinking FE engines. But traditionally we all know the difference between a 429/460 big block and the FE engines. Even though the FE engines are physically a BIG BLOCK.

      • OnAllCylinders Staff says:

        You’re exactly right gentlemen. We’re sometimes guilty of using the slang “big block” moniker too often when talking about Ford engines, and it’s especially confusing here in regard to the 385- and FE-series. We’ve adjusted the paragraph above to be more clear–thanks for the heads up!

        • Technically Ford never classified their engines as big block/small block! They classified them in families. 335,385,FE.

        • Question, i have a older 351M and a 1994 460 will they bolt up to the same transmission Sorry, I’m a old Pontiac guy 50s 60s and up to a 72. But i have a few fords, mercury’s and Lincoln’s and 30s, 40s and 50s Chevrolet’s and 1 55 olds But i own some Honda’s cars and bikes and a few Harley’s and 1 dodge a magnum. NO i do not own a salvage yard, most of these run and drive.

    • Daniel Wilson says:

      Rick…to add to your observation about those really cool guys that boastfully claim to own a killer Cleveland but can’t name a single difference between a Windsor and a Cleveland. Let’s include the next level of cool dudes that “ Own a BIG BLOCK Cleveland engine” in their totally radical rides.

      I used to try to explain the how and why reasons Ford’s Cleveland Small Block shares some of the same internal dimensions as the Windsor but it seems useless.
      The ignorance is bliss beat goes on…..

    • My first truck in early 1982 was a 1965 Ford f100 short wide with a 352 c.i. with a three on the tree and metal bed floor ( no wood ) . I loved that truck but sold it in 1985 when I went in the army . Would love to find another some day that I can afford

      • My first truck in 1977 was a ’64 F100. Tank behind the seat, long bed, three on the tree. I too loved that truck. The 292 “Y” block downfall was the external oil pump. Driving from New Jersey to Great Lakes Naval Station for school, the oil pump cover decided to come loose. Damn it! I found a 352 from a ’56 wagon. It paid going to Navy diesel school. I so want to find another.

  6. Pingback: Afinal, qual é a diferença entre um motor V8 Windsor e um V8 Cleveland? - FlatOut!

  7. Pingback: Afinal, qual é a diferença entre um motor V8 Windsor e um V8 Cleveland? - Assobrav

  8. The Cleveland, 400 & 351M were all part of the Ford 335 design engine family. The Cleveland (both 2V & 4V) was introduced first in 1970, followed by the (taller deck) 400 in ’71. Note that FoMoCo NEVER applied the “M” label to the 400 & it was in production a FULL 4 yrs BRFORE the 351M came out in 1975 AFTER the original Cleveland was discontinued in North America. The 351M remained a passenger car engine ONLY until 1977 when it appeared in trucks. Both it & the 400 disappeared forever after 1982. A VERY GOOD read is the “New Muscle Power” booklet published by Ford announcing the 351 Cleveland for 1970; mostly about the 4V M-code. There’s that “M” again to confuse the less intelligent……….

    • What alot of people don’t realize, is the 351m was actually a 400 destroked to a 351, the two engines used the same block and rod length, with the only difference is being the compression height of the Pistons, being the distance from the rist pin to the top of the Pistons, and the 3.50 inch stroke crank. The 400 was in production for 4 years before the engine was modifed to the 351 that was the replacement of the Cleveland engine. The 351c is the only 351 proformace engine for build. The engine was available in a few different varieties. The proformace style Wich were all 4v engine which had the same intake and exhaust ports that the 302 boss had, the engine was available as a Cobrajet version, boss, and H.O. version. Of course HP severely was affected after 72 but with fuel supply shortage and emissions this was part of the end of the Cleveland.

  9. After reading all the comments, I do know one thing. My 34 Ford Coupe, has a 351 Windsor. Thanks to all.

  10. Dominic Hermes says:

    Thanks guys this is a good read I learned a lot I have a 77 F-150 with a 351M and my land lord told me we could put a 351C or 351W in instead I think I will just rebuild the one I have

  11. Pingback: Project Warrior 2.0 (Part 2): Putting Together the Build Plan for an Arctic-Bound '78 Bronco - OnAllCylinders

  12. I have a 1978 Country Squire with a 351M/400M. Transmission is gone and I’m told I can just pop one out of an old F150 to replace it. Can anyone authoritatively confirm this?

  13. Hey all,

    What if the letter “M” is cast into the corner right-side of engine near head??

  14. Pingback: Mailbag: Budget Performance 351W Upgrades for a 1969 Ford Mustang Mach 1 - OnAllCylinders

  15. Mark Cruwys says:

    Awesome information. Having owned both the 351 Windsor and Cleveland versions in Australia, I didn’t realize there was an “M” version.

    Cheers Mark C

  16. Have a 1979 Ford Bronco With the 351M was told the Broncos was for two years only with this Version. had Headers four barrel and a Body lift

  17. Hey guys. I just pitched a 351m. I have had Cleveland’s and Windsor’s but never heard of the 351m. Is it going to be stupid to try to build this engine. I saw that it only came in 2barrells. Are they a after market intake 4barrel I can get for it? Will a 400 intake work on it. Would really appreciate any and all tips on this subject. Also any tricks to beef it up.
    Thanks

  18. Keith patterson says:

    In my question I meant I just purchased a 351m. Darn spell check. Lol

  19. Mike Legarth says:

    Can someone help. How can I indentify a Ford Cleveland 351 V8 small block from US, 1972, by the engine casting number? With other words, what numbers should I find on the block?

  20. Frederick Chavre says:

    All I know is that Dad and I went down to the Ford dealer and bought Mom the only ‘off the lot’ new car ever in our family. That Torino GT had the 11/1, 351C. I graduated a few months later and Mom let me buy it from her for my college ride. What a burner!!

  21. Also, any 351c performance cam, timing set, headers, will fit the 400 or 351m.

  22. I miss my 66 merk wagon w/ 2bbl 390 it steerd well stopped very comfortably and it had satisory get up and go when it was rebuilt I spifyed Rv Cam and sodiem filled valves thair is other things besides displacement , like symbosios universal water pump valve covers bolt patterns anceliery equipment and perches.

  23. Well, quick question. I just bought s 1992 f150 with a 300 straight 6cyl. 1 owner Alabama truck and 115000 miles, and great body-chassis. So many people are suggesting to build the 6cyl but i would like to make a rockin 2wd street toy. Any suggestions?

    • Alexander Golen says:

      I would keep the 300cid nearly indestructible. Friend of mine had a 300cid in a Mercury Capri with a 4 speed manual. He used to blow the doors off of the stock 5.0 Mustangs. Look up Cliffords 6 cycliner performance parts. You can get Offenhauser four-barrel carburetor intakes full length headers. It is possible to build a high performance inline 6-cylinder and in my opinion worth it. The inline 300 6 has been used I’m construction job sites the power generators and compressors for ddecades. As far as I know still used today because they run forever.

  24. Also most of the people who are suggesting to build the 6 race late model or modifed cars. I want v8 power and sound

  25. Scott Hunter says:

    I have a question maybe someone can answer. Are the fuel pumps for a Windsor, and a Cleveland interchangeable? Are the bolt patterns the same? If so, will the fuel pump for a Windsor run a Cleveland?

  26. I had a 72 galaxy with a 400 and a c-6 it was a two door 2.75 nine inch . It would routinely get 21 miles to the gal at 65 miles an hour.
    It had great tourque does anyone know if it would have had closed chamber heads and also why the 400’s that I encountered in the f150’s sucked fuel so badly and had such poor power?

  27. Hi Guys,

    anyone know the cylinder bore of a 351C-2V pls?

    • Stock bore size was 4.000″. This is true of all 351 engines as well as the 302, 289 and 400. The stroke was used to change the displacement of them.

  28. In my younger days of working on cars, my parents had a 78 LTD II. It had a 351 M and a C4, so just realized they made a C4 with a 335 series bellhowsing bolt pattern?

  29. I just bought a 69 Mach 1 with a 351 Windsor (M code) and was wondering what oil viscosity to use in it. Thanks

  30. How many 351 c 4v were made in 1970?

  31. V is for Venturi like 2v /2bbl 4v/4bbl like a two or four bbl carb

  32. Cleveland heads fit 302 with some work to water passages hence 302 boss also can make 351 clevor .not sure if would fit 289

  33. Reddawg jenkins says:

    Keep ur pics it stands for midland its just easier to identify it as modified since it was derived from the cleveland which had an oiling problem that done it in even though the routing of 1 hose cures the problem

  34. Val Dennis says:

    Will the 351 Cleveland fit my 1994 Lincoln Town Car? 281 cubes is not big enough and I don’t have a big block.

  35. Lets not forget the Cleveland was used by several other companies, most notably Detmasa in the Pantera…. that was a fun ride, but always had over heating problems in Texas.

  36. Detomaso… fat fingers on small phone.

  37. Harold Force says:

    Had a ’69 Mustang with the 351 C – would only run on Sunoco 280 or Super Shell. Told it had the highest compression ratio of a Ford engine. 4 speed wide ratio (with bad sincro in second from the factory), and about (?) a 3.30 rear. We were doing road rallies in the NE. 60 in under 6 seconds and accelerated in 4th as if still in 2nd. Needed Boss front spoiler to keep front wheels on the ground. Went from that to a ’71 250 Z! Too much back story…

  38. Robert Fuller says:

    A easy way to tell an M engine is the fuel pump, the 2 attachment bolts are vertical..

    The cleavland exaust manifolds have much bigger ports than a Windsor & won’t interchange..

    Windsor exhaust manifolds will fit 289’s

  39. Harold Swanson says:

    I have a 1963 ford galaxy that I’m restoring and I have a 351w engine and c6 trany. The reason I know it’s a windsor is because the thermostat housing sticks straight up.

  40. Harold Swanson says:

    up

  41. Barry Aldrich says:

    Hi chuck I think it should bolt up. Barry

  42. Michael parisio says:

    Clevelands have two fuel pump bolts one on top and one on the bottom. How do I know?
    I own one in a 71 stand. So I guess a couple of you just like to flap your gums.

  43. Philip Andrews says:

    I remember my late fathers 1977 F250 4×4 Custom crew cab 4 speed standard with its 351W. He bought that truck new but cursed the engine every time he had to drop down into second gear with his foot through the floor going up a extra steep hill. It was a pretty gutless engine for a truck that size and definitely not much of a highway cruiser. Amazingly the truck still exists today but currently has a 390 in it. I’d give anything to be able to go for a drive with him in that truck one last time.

  44. Bought an F-350 custom, (with a heavy service bed and crane) brand new with the 351m 2V in 1978. Had the same problem having to downshift to get up hills. Could do 57 MPH in third with the engine close to 4000 RPM. The problem wasn’t the engine, it was the gearing. One supposed remedy to poor mileage during the gas crunch was high gears so the engine was turning slower at 70 -75 MPH. Unfortunately, I had to use the granny gear to start out, or waste the clutch. Bad idea on Ford’s part, especially when the truck was loaded heavy.

    Lost the 351 after only a year and couldn’t wait for Ford to rebuild it (warranty issue), so bought a rebuilt 400 from American Engine Exchange (terrible mistake). Put a high-flow eldelbrock intake and Carter 650 4 barrel on it with an RV cam and felt like it doubled the HP. Had it running in 3 days. Hauled that heavy truck around like it was nothing but still had the way-too-high gear problem on long, steep inclines. On the flat however, the high gears let that truck run over 100 mph in 4th gear! (Not that I did it very often.)

    Still have the truck today with the 5th or 6th motor in it. Went back to the 351 2V with better heads and the thing has good power and … gets 14 MPG … remarkable when you consider the 11,000 Lb. GVW it’s got.

  45. I really liked your info on the 351. I always been a huge fan of that motor. I just had an opportunity to buy a good rebuilt 351c 2v. I have a 67 Mustang and put it in it. I can’t find in any forums that if I need to change the motor mounts. from what I understand If it was a Windsor no, but a Cleveland yes. Is this true? Thanks for you time.

  46. I have a 73 mustang the original 351c matching # was stolen from my garage just wondering what you would think this would be valued at ? first the engine alone and the fact I lost the matching # engine. Thanks

  47. Lee Nicolle says:

    Clevo and M engines had some anomolies. There is a few 400s with Clevo b/h pattern for cars with FMX trannys.72-73 I believe.
    71 only 400s had 9-1-1 comp, the rest around 8.5. Though buy FM pistons that are way down the hole and you will end up with about 7.8. Mine now has 60cc 302C [Australian] heads and gets 9.1-1 It was far sharper with nearly 10-1 on 98 octane unleaded.
    351/400M and 351W all share the 3″dia mains so dont rev them or they spin a main.Why did Ford ever make them so large? I believe some aftermarket W blocks use Clevo size and they are too big as well. But a bit better.
    The 400 is suited too what it was installed as as a engine for 2 tonne tanks.Mine is a 71 LTD. Even the 2V intakes really are too big. A 400 Performer gives them a Chev race port intake runner. And that is about 75% the size of a 2V port
    I have a mild race 351 Clevo, 440hp @ 5800 which is better than I expected.11-1 Stock 302 heads with Ferea valves and screw in studs, Holley intake, 750HP, 302 rods, ACL Race series pistons and a hydraulic race cam with Crane rollers. The long rods give it so much low end torque it is hard to get off the line without frying [semislick race] tyres. It is in a budget road race car

  48. Aaron M Kane says:

    almost sounds like you could say that ford had a small medium and large .

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