Ford’s 351 Cleveland V8 is a legend in American high performance. A nice compromise between a small block and a big block, enthusiasts love it for its brute demeanor and ability to make abundant power.
However, there is a lot of myth and folklore surrounding the 351C’s development. We recently had a conversation with retired Ford engineer Bill Barr, who was there to see it all. He set a lot of the misconceptions to rest about the Cleveland.
Barr worked in Ford engine development and engineering for most of his career. He managed Ford’s FE big block program, including development of 428 Cobra Jet. He also worked on the 1969-70 Boss 302 engine program.
No one, including other career Ford engineers and product planners we’ve spoken with, could remember where the 351C originated. Barr told us the engine was conceived in Ford’s Advanced Engines unit—something of a secretive “Skunk Works” within the company. The plan was to scale the number of Ford V8 families down to just two—one small block and one big block. The big block became the 385 Series 429/460. The small block was named the 335 Series. Initial displacement was set at 335 cubic inches, but that was updated to the 351 and 400 CID engines we are familiar with.
Ford’s original game plan for the 335 Series was to build a V8 engine with fewer potential leak points and more perfect mating surfaces, wider main bearing journals, and better gasket/sealing technology. Ford engineers believed the 351C had fewer potential leakage points thanks to a steel plate timing cover, a better relationship between the oil pan and block, and a cooling system that bypassed the intake manifold entirely. Coolant flowed across the block instead of through the induction system, which reduced or eliminated leaks and reduced induction temperatures.
Barr admits he hated the 351C. It made little sense to him as a seasoned Ford engineer who understood engine architecture and where this engine fell short. It was too heavy for one thing. The oiling system is one of the worst in Ford’s history with oil starvation issues that have plagued racers and performance enthusiasts for decades. However, Barr loved the 351C’s cylinder heads and adapted them for the Boss 302. More on that.
Smokey Yunick and the Indy Engine
Here’s another twist to the 351C story. In 1968 Ford’s then President, Semon E. “Bunkie” Knudsen, asked racing legend Smokey Yunick to help develop an engine for Indy competition. Yunick had a long and successful history with General Motors including input on Chevrolet’s Mark IV big block introduced in 1965.
Ford’s prototype Indy engine was very similar to the production 351C. It had a skirtless block and the same bore and bolt-hole spacing as the 289/302/351W small block. The heads had poly-angle valvetrain geometry with angled pushrods that crisscrossed over one another and ports even larger than the 351C-4V castings. The Knudsen/Yunick-inspired Indy Cleveland went the way of Knudsen himself when he was fired by Henry Ford II in 1969 for failure to adapt to the Ford culture. But much of the technology was used in the production 351C. Now you know.
The BOSS 302/351C Connection
The 1969-70 BOSS 302 engine was developed in the wake of the ill-fated 302 “Tunnel Port” small block of 1968. Built for SCCA Trans-Am competition, the Tunnel Port was a disaster. The engine did not make peak horsepower until 8,000 RPM, which led to catastrophic engine failures and embarrassing losses. Racers were scattering Tunnel Ports all over racetracks during the 1968 season.
When our engineer friend Bill Barr learned of the high Tunnel Port failure rates, he began searching for quick answers within the company. As mentioned earlier, he found a suitable solution at Ford Advanced Engines’ 335-Series program. He borrowed a pair of 351C cylinder head castings and went to work. The bolt pattern and bore spacing were the same between the small block and the 351C so the heads would physically bolt on. Barr did need to have special pistons made. He also revised coolant flow through the Cleveland heads so they would work with the “wet” intake manifold of the 302 engine. Thus, the Boss 302 was born. Ford’s SCCA-Trans Am wins in 1969-70 and the desirability of the Boss 302 Mustang street cars speak for Barr’s excellent work.
The 351M and 400
The 351C had two cousins. The raised-deck 400 CID engine replaced the 390 and 428 FE big block engines in 1971. It had 4.000-inch bores and a 4.000-inch stroke to create a “square” bore/stroke ratio—in other words, an engine big on torque to pull around F-Series trucks and full-sized Fords and Mercuries. Ford never identified the 400 as the 400C or 400M. It was always known within the company as plain old 400.
After Ford ended 351C production in 1974, it decided to make a new 351 cubic inch engine by destroking the 400 to 3.500 inches. Designated 351M (Modified), it was a bean counter brainstorm conceived to reduce manufacturing costs. However, it was a terrible idea because you had less displacement and power in an engine that weighed the same as the 400.
Both the 351M and 400 came with a 429/460 big block bellhousing bolt pattern, though early production 400 engine blocks have big block and small block bell patterns. Both engine used the 351C-2V heads with open chambers, which were prone to detonation issues.
Although the 400 and 351M engines get a lot of criticism, there’s more to these engines than you see on the surface. The 400 could have been factory-grown to 430 to 450 CID, creating a ‘mid-sized’ engine with a big-block personality without the weight penalty. This is something you can do yourself with a stroker kit.
Get more info on Ford’s 351s in What’s the Difference Between a Ford 351 Windsor, Cleveland, or Modified Engine?
What’s In A Name?
The ”Cleveland” name for the new 335 Series engine resulted from an identity crisis in Ford dealer service departments and automotive repair shops. Ford already had the 351W, which was a raised-deck 289/302 engine with 4.000-inch bores introduced in 1969 to compete with GM’s 350/400 cubic inch engines. When the 351C arrived in 1970, there was confusion among the service technicians though the two engines were vastly different in appearance and easily identified.
Ford issued a Technical Service Bulletin addressing 351 CID V8 engine identification. Because the 351W was produced primarily at Ford’s Windsor, Ontario foundry and engine plant across the river from Detroit, it would be known as the 351 “Windsor”. The 351C was cast and assembled at the Cleveland foundry and engine plant in Brook Park, Ohio, so it became the 351 “Cleveland”.
Fun fact: The 351C was manufactured using a new hot testing process at the Cleveland plant. The engines were fired in a “merry-go-round” process before they were shipped to Ford assembly plants.
The 351C in Australia
The 351C was introduced in Australia at the same time it was offered in North America. In the beginning, Australian Falcons were fitted with 351C engines produced at Ford’s Cleveland engine plant. Blocks were also cast at Cleveland and shipped to Australia. In due course, Ford Australia began producing complete 351C engines along with destroked 302 cubic inch Clevelands. The engines were made from 1972 to 1982.
Here in the States, Ford packaged the 351-4V heads with small wedge chambers and huge intake ports. These worked well at high RPM but weren’t the greatest on the street where low-end torque was more critical. The Aussies gave their Cleveland cylinder heads the smaller 61-64cc combustion chambers from the 4V heads and the smaller 351C-2V ports for good street torque. The 302 sported a different head entirely with smaller 57-61cc wedge chambers.
As a rule, Aussie Cleveland castings don’t have Ford North America casting numbers. If you find a Cleveland block without a North American casting number and a “GF”(Geelong) foundry designation, you’ve found an Australian block. However, some believe North American molds were shipped to Geelong to make the first Aussie castings, which means there could be some with North American Ford casting numbers. Another belief is Ford North America shipped discontinued Cleveland casting molds to Australia in 1974 when production ended in the States.
Very few production Australian 351C blocks had four-bolt main caps. Those fitted with four-bolt main caps were either converted or were experimental blocks.
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