We will probably never know the entire story behind the origins of Ford’s 335-series middle-block 351C and its tall-deck brethren, the 400 and 351M. What we do know is what these engines did for Ford during their brief North American production lives in the 1970s and even longer production periods in Australia. These engines didn’t live long enough in production nor did they realize their great potential as factory high-performance engines due mostly to the unfortunate timing of tougher federal emission standards and higher auto insurance rates. It arrived during a period of changing attitudes about high-performance automobiles.
The 335-series 351-ci engine introduced for 1970 quickly became known as the “Cleveland” for identification purposes because there was also the raised deck 289/302 engine displacing 351 ci known as the “Windsor” introduced a year earlier in 1969, which made things confusing for Ford dealer service technicians and shop mechanics everywhere. The visual differences between Cleveland and Windsor are obvious with huge, broad-shouldered valve covers on the Cleveland and traditional, narrow small-block Ford valve covers on the Windsor. Ford issued a technical service bulletin shortly after the 351C’s introduction differentiating the two types of 351-ci engines and how to identify them. Ford came up with the words “Windsor” and “Cleveland” to describe the two 351-ci based engine families and so they have been used for decades.
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The broad-shouldered 351C with its wide valve covers and poly-angle valves got the “Cleveland” name for the plant and foundry of its manufacture. The 289/302-based 351-ci engine became known as the “Windsor” for its Canadian birthplace across the river from Detroit. If you have a 351, you have either a Windsor or a Cleveland. And “Cleveland” has always denoted muscle and power. In fact, based on what I’ve learned from Ford insiders who were there at the time, the original game plan was to ultimately drop the 351W and keep the 351C, which in theory had better block architecture and growth potential. The 351W was a stopgap, mid-displacement, V-8 Ford hurried into production to compete with middle-inch Detroit V-8s such as GM’s 350s, Chrysler’s 318 and 340, and AMC’s 343 and 360.
This book is all about the 351 Cleveland, or 351C, which was produced in North America from 1970 to 1974 and in Australia from 1972 to 1982. It is also about the raised-deck version of this engine known as the 400 and the 351M. It has never been confirmed with any certainty what the “M” means, from anyone including Ford Motor Company. Some say “Midland” and others say “Modified,” including Ford. The 400 has often been called the 400M in the years since 1975 but when the 400 was destroked to become the 351M, Ford didn’t call the 400 “400M” in factory publications.
The 400 was produced from 1971 to 1979 as a replacement for the 390-ci FE big-block. In 1975, the 351C was dropped and the 400 was destroked to displace 351 ci and became known as the 351M, which was produced through 1982. This was an obvious effort to consolidate both displacements into one block. The 351C, as well as a lower-displacement 302C, was produced in Australia from 1972 to 1982.
There are so many unanswered questions about how the 335 engine came to be, especially considering it copped a number of General Motors engineering nuances (wide cylinder heads with poly-angle valves and huge ports like a big-block Chevy, and block architecture on a par with Oldsmobile with a 12/6 fuel pump and steel timing cover plate). However, the engineering that went into Ford’s all-new 351 C for 1970 was remarkable for its time. What made the new351 C extraordinary was its cylinder head with a near-perfect wedge combustion chamber with just the right amount of quench with early 4V heads. What hurt the Cleveland was an ill-timed debut; Ford got out of racing in 1970 right after the Cleveland’s introduction.
Though the 351C has a reputation for power and performance, most were garden-variety vanilla mills with 2-barrel carburetion and open-chamber heads fitted to intermediate and full-size Fords and Mercurys. They delivered snap, but not the kind of screaming, high-RPM horsepower the Cleveland was developed for.
The Cleveland shares the same bore spacing as the 289/302/351 engines; however, it in no way has the same block architecture. The 335 block is heavier and thicker than its Windsor counterparts— a casting conceived for durability with a completely different oiling and cooling system, smaller (yet wider) main journals, and a dry induction completely bypassed by the cooling system.
From a performance enthusiast’s standpoint, the Cleveland was a disappointing mill because, as enthusiasts, we could see great potential in this engine, yet there were not enough factory performance pieces available at the time. This continues to be true even today because the Cleveland’s production life in the United States was all too brief and parts all too scarce. For those of us in North America, this has long meant looking to Australia for desirable Cleveland pieces, such as cylinder heads never available north of the Equator. For Ford North America, the Cleveland’s focus became more federal emissions than performance, which is why the Boss and High Output Clevelands lived such a short time here. In fact, the 351C High Output was dropped well before the end of the 1972 model year.
Based on what buff books had to say at the time, the 351C fell short of expectations. Hot Rod magazine had this to say about the new 351C in August 1970: “While the Cleveland is inherently better in design and potential than the Windsor with a good many compromises.” Hot Rod went on to say, “The stock hydraulic cam has .430-inch intake lift and .450- inch exhaust lift. Intake valve duration is 268 degrees, exhaust is 280 degrees, and overlap is a scant 37 degrees. The canted valve arrangement is a good idea, but for reasons of production and ease of assembly, a cylindrical fulcrum is used to hold the individual stamped steel rockers in place.”
Hot Rod sung the Cleveland’s praises as a good production engine, but concluded the engine fell considerably short of the mark when it came to performance. Ford’s Ak Miller teased Hot Rod readers with a dynamometer test-cell experience in Long Beach, California, with an Autolite in-line carbureted 351C to demonstrate the engine’s potential. Hot Rod speculated what it would take to reach the 351C’s potential, including Boss 302 cylinder head and valvetrain modifications to accommodate adjustable rocker arms, screw-in studs, guide plates, and the rest of it.
This is the 351C-4V most know, with its broad-shouldered attitude and wide valve covers. Although the 351C is known for its power potential, most were the vanilla 2-barrel version with open-chamber cylinder heads.
Here’s the more common 351C-2V engine, easily identified by its smaller air cleaner and Autolite/Motorcraft 2100 or 2150 2-barrel carburetor.
The 351C-2V Ram-Air of 1973–1974 leaves most of us scratching our heads because the 4V engine was not available with Ram Air that year due to tougher federal emissions standards. The 2V passed federal emissions; the 4V did not.
Ultimately, Ford presented hot rodders with the Boss 351C engine with a hot mechanical cam, adjustable rocker arms, screw-in studs, guide plates, and one heck of a middle-block powerhouse. In Hot Rod’s 1970 351C dyno testing with Ak Miller, it was able to get nearly 400 hp with no attention being paid to torque. Of course 400 hp is laughable by today’s standards because the 351C stroked to 408 ci with the right heads can produce more than 600 hp courting 8,000 rpm.
I suppose you could call it ironic we call this engine the Cleveland considering Cleveland castings were also produced at the Windsor, Ontario, foundry. All you have to do is look for “WF” on Boss 302 and 351C heads to discover this irony. There are also Michigan casting pieces, which appear to have no foundry markings. However, all 351C engines were assembled at Ford’s Cleveland Engine Plant #2. Australian Cleveland engines were cast and assembled atthe Geelong engine plant just outside of Melbourne from 1974 to 1982.
You don’t need to rub your eyes. Ford Australia did a 302-ci Cleveland with a 3-inch stroke and 4-inch bore. The Aussie 302C is a destroked 351C. According to one Australian source, the 302C head was similar to the 351C wedge head except for smaller 58-cc chambers to keep compression where it belongs. If you’re thinking about 302C heads for your 351C, forget it. Compression would be too high at 11.0:1 with today’s pump gas.
To understand the Cleveland’s performance image, you have to know a little bit about how this engine came to be. Although there’s a lot we still don’t know about its development, here’s what we do know. The 351C was developed to be a high-performance street and racing engine from the start, according to George Pence of the popular “Clevelands Forever” website (www.351c.net). “I have found the best way for me to understand the Cleveland is to first respect the knowledge and experience of the engineers who designed it. I am convinced every aspect of the design of the 351C 4V was deliberate,” Pence comments in the website, “If some design aspect seems fudged to me I have learned it’s because I don’t understand WHY they designed it that way. In other words, I’m the one who is ignorant, not the engineers who designed the 351C 4V.”
Pence further comments, “The engineers who designed the 351C-4V were heavy hitters in the world of race engine design. These guys weren’t novices. Bill Gay’s group represented an amazing depth of experience in the design of state-of-theart race engines. With all due respect toanyone out there that disagrees with me, I believe anyone among us who critiques the engineering of the 351C 4V is like one of the Catholic clerics who opposed the heliocentric science of Galileo. None of us have the knowledge and experience those guys were privileged to have. We are not in the same league. When it comes to engine design we are fumbling in the dark compared to the 351C 4V engineers.” Pence is accurate in his observations regarding theCleveland’s development. What he has to say is enlightening.
Pence goes on to say, “The Cleveland was a racing engine from the get-go; heavy duty and designed to get out there and race. It was designed by the same people who brought us the legendary Feseries 427 big-block with its cross-bolted main caps, heavy main bearing webs, and side-oiler design—all features intended to help an engine live, and win.
“These same engineers designed the 351C for the same type of racing yet they included none of those features. Had they forgotten everything they learned? Had they gone daft? Were they idiots? You can’t straddle the fence on this issue. They were either idiots and decided their new engine didn’t need those features, or they were up to something new with the 351C 4V—something very deliberate. Engineers knew they would have to contend with the same forces which required cross-bolted mains, thick bulkheads, steel cranks and side oiling when they had previously designed the 427 FE, “ Pence observes. “The 351C 4V benefited from the new ways of doing things the engineers had learned while designing racing engines such as the Indy racing engines of 1963–1965. Design of the Cosworth DFV Formula One engine was also wrapping up in England in 1966. The 427-powered Ford GT40 was dominating LeMans and the World Endurance Racing series in 1966.”
The high-performance 1971 Boss 351C and 1972 351C High Output are the same except for compression ratio and horsepower ratings (SAE net for 1972). Both are ram-air engines. The 1972 351C High Output is extremely rare. Very few were produced, and even fewer have survived to today.
The 351C-4V engine for 1973–1974 was never available with ram air though enthusiasts like to upgrade. This one has its original large air cleaner with a vacuum-operated, auxiliary air door for wide-open-throttle operation.
The 351C-4V engine for 1973–1974 was never available with ram air though enthusiasts like to upgrade. This one has its original large air cleaner with a vacuum-operated, auxiliary air door for wide-open-throttle operation.
The 351C block has the same decks and bore spacing as the 351W, which is the only thing these engines have in common. This makes head swaps possible from 351C to 351W to create a “Clevor” engine. What makes the 351C block different is its oiling system, steel-plate timing cover, 12/6 o’clock fuel pump, and smaller 2.7500-inch main bearing journals. The front of the block closely resembles Oldsmobile’s Rocket V-8 with cast iron wrapped around the timing set. Coolant bypasses the intake manifold and is contained in the block and heads.
Ford’s engineers took what they learned from the 427 FE and applied it to the Cleveland’s development. Ford termed the Cleveland “an engine that reflects the racing heritage of Ford products on the world’s toughest race courses.” The objective was to mass-produce a high-performance engine as inexpensively as possible employing new technology and manufacturing methods. The 351C had wider main bearing caps, which eliminated the need for cross bolting. Ironically, Ford has since gone back to skirted blocks and cross-bolted main caps in its series of overhead cam modular V-8s, which has proven very successful.
Pence further reflects, “When the 351C 4V entered the scene in 1970, NASCAR was dominated by 7-liter endurance racing engines that cruised around the ovals at about 7,000 rpm making about 500 bhp. Endurance camshafts of the day had about .600-inch lift. It was no accident that when equipped with a .600-inch lift endurance racing camshaft the 351C 4V makes about 500 bhp at about 7,000 rpm. From 5.75 liters! 7-liter hemi engine torque and horsepower from 5.75 liters at the same RPM. Engineers hit their mark dead on. No mistakes. No getting lucky. It was all very deliberate. The Cleveland is an amazing racing engine. It just lacks the curb appeal of the Hemi engines with their big aluminum heads and centrally located spark plugs.”
What Pence so eloquently says is the 351C was ahead of its time with its poly-angle valves, generous ports, near-perfect combustion chambers, and meaty bottom end. The Cleveland’s4V cylinder heads were designed for a hefty .600-inch-lift cam and 7,000-rpm performance making a solid 500 hp in1970. These are performance numbers quite at home in the twenty-first century with its alloy heads and super fl ow numbers.
“As the 351C-4V-powered Fords thundered around the banked ovals at 7,200 rpm for 500 miles, they did so with complete reliability. They were reliable in spite of their nodular iron cranks instead of steel cranks, in spite of their thin wall block instead of thick bulkheads, in spite of their lack of cross bolting AND in spite of their lack of side oiling. The engineers achieved the 351C4V’s reliability with all those short cuts because they weren’t short cuts. Like the wide main bearing caps, the engineers deliberately chose engineered solutions instead of brute force to make the engine reliable. The 351C did not have a reputation for problems in the early years,”Pence observes.
The 351C’s wide cylinder heads offer canted (poly-angle) valves for improved crossflow. Four basic types of cylinder heads were cast to the best of my knowledge—large port/wedge (closed) chamber, small-port/ open chamber, large port/open chamber, and small port/wedge chamber. The small port/wedge chamber is a Ford Australia head, which offers the optimum combination of 2V size ports for better torque coupled with wedge chambers for improved quench and more desirable compression.
What makes the 351C different from the 351W is a dry intake manifold. Coolant bypasses the intake manifold, an unusual step for Ford, with the thermostat located in the block along with a brass restrictor.
Pence punctuates the 351C’s performance message informing us what went into the development of Ford’s out-ofthe- blue middle-block V-8. The 351C and its fans were victims of unfortunatetiming when it entered the marketplace. In North America, the Cleveland went vanilla and went away in just four short years. In Australia, bold “no worries” Aussies took the Cleveland to its potential and stayed with it for more than a decade. Some forty years later, the Aussies continue to bring us great Cleveland performance parts including alloy heads as well as an anticipated supply of aftermarket blocks.
Written by George Reid and Republished with Permission of CarTech Inc
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