Block architecture closely...
Block architecture closely resembles Oldsmobile V-8s of the period, with the timing set completely wrapped in iron with a steel front cover, an iron water pump, and a 12/6 o'clock fuel pump bolt pattern. Do you see the Oldsmobile connection?
Ford's 351 Cleveland is legendary for the performance it has given us for 36 years. However, we admit to being confused by Ford's decision to manufacture the 351C . It already had the 351W, a raised-deck 289/302-based mill conceived to go after Chevrolet's 327 and 350ci small-blocks. The 351C was loosely based on the 289/302, with identical cylinder spacing, but it had a different oiling system and an Oldsmobile-like front timing cover, main bearing caps, and fuel pump configuration.
Although we have never been able to confirm this theory with Ford insiders, we're convinced Semon E. "Bunkie" Knudson had everything to do with the 351C's conception. Knudson was hired away from General Motors by Henry Ford II to run Ford Motor Company during the late '60s. When Knudson arrived in 1967, the 351W was already well underway and scheduled for production beginning in 1969. The 351C was introduced in 1970.
We base our Knudson 351C theory on design elements that it shares with notable GM V-8 engines. The same can be said for the 385-series Ford big-block (429/460 ci), which has design elements also borrowed from GM just about the time Knudson was running Ford. The Cleveland's oiling system, timing cover, and cylinder heads distinguish it from traditional Ford V-8s. The 351C's canted-valve (poly-angle) cylinder heads are obviously borrowed from big-block Chevys. Its oiling system, timing cover, and fuel pump configuration are clearly influenced by Oldsmobile-with the exception of the fuel pump's location on the opposite side. It is the only Ford V-8 ever produced with a 12/6-o'clock fuel pump bolt pattern like Oldsmobile's.
We will never know for sure, but you can bet Knudson's engineering people walked into Ford and speculated about what could be done with those stifling small-block Ford heads. The result would be the canted-valve, large-port Cleveland/Boss 302 cylinder head. What's more, they probably did the same thing with Ford's LeMans-winning FE-series big-block-replacing it with the 385-series 429/460 big-block later on. We will go out on a limb by saying each of these engine families survived, because it was undoubtedly a political battle between Knudson's GM outsiders and Ford's established engineering people.
When Ford introduced the 351C in 1970, it was embraced by enthusiasts for its large-port, poly-angle valve heads and its ability to produce lots of power. The aftermarket promptly went after performance buffs, setting them up with single- and dual-plane high-rise manifolds, tunnel rams, ignitions, hot cams, carburetors, and more. Big-time drag racers took the 351C and put it to work in 8-second Ford compacts, such as the Gapp & Roush "Tijuana Taxi" Maverick sedan. Saturday-night warriors did the same thing with Mustangs, Fairlanes, Torinos, and Cyclones, going after the competition with Ford's newest V-8. The 351C wound up being a phenomenal success during the '70s.
What helped the 351C also contributed to its demise in 1974. When Knudson was fired from Ford in 1970 and replaced by Lee Iacocca, we're convinced most support for the 351C went with him down the elevator to Michigan and Southfield. Of course, Ford didn't give up the 351C completely. It raised its deck to create the 400M for 1972, which replaced the FE-series 390/428ci big-block in passenger cars. In 1975, the 351C was dropped and replaced with a destroked 400M known as the 351M-both had big-block bellhousing bolt patterns.
We would like to hear your thoughts about the Knudson/351C connection. Can anyone answer us about the 351C's origins? We invite your feedback at Jim.Smart@sourceinterlink.com.
Getting 351C Performance
Ford's 351C is challenging because its cylinder heads were never practical for street use. This is a high-revving V-8 designed to do its best work on the racetrack, thanks to big-port heads, poly-angle valves, and wedge chambers. What makes it successful on the racetrack is what makes it a dog for street use because we need good low-end torque for the commute. Anyone building a Boss 302 understands this because Boss 302 engines were fitted with modified Cleveland heads. It was designed for high-revving Trans-Am racing, not fetching groceries. The same can be said for the 351C.
To meet the need for low-end torque, Ford's North American engineers opted for smaller intake and exhaust ports on the 351C-2V head along with open chambers to get compression down. The downside to this open chamber is its detonation tendencies. It tends to create two opposing flame fronts under mod-erate to heavy acceleration. The very thing it was intended not to do-ping-it does with great regularity. Smaller wedge chambers actually ping less than open chambers thanks to shape and quench area.
In Australia, Ford engineers improved the U.S. 351 Cleveland head with small 2V ports and tight 4V wedge chambers. Aussie Cleveland heads are the hot ticket for Clevelands with generous build budgets and access to these heads from Down Under
Like the Oldsmobile Rocket...
Like the Oldsmobile Rocket V-8s of the era, Ford's 351C, 351M, and 400M have wide main caps fore and aft, with a similar oil pan design. Where the Cleveland differs from Olds is a front sump design. Olds has a rear sump.
John prefers Speed-Pro forged...
John prefers Speed-Pro forged aluminum pistons with coated skirts for reduced friction and improved reliability. Here, he rolls on rings and readies slugs for installation. John coats the skirts with assembly lube, and applies a thin film of 30-weight engine oil to the cylinder walls.
The 351C block offers excellent...
The 351C block offers excellent bottom-end support and can take high revs without breaking a sweat. This makes it stronger than a 351W block. The downside is an oiling system that's inadequate, as it comes from the factory. Cam bearings and lifters get oil before the mains, which causes oil starvation issues under extreme conditions. Experienced Cleveland builders opt for all kinds of oiling system mods, including an external oil line from the front of the block to the rear to improve oil flow at the mains. A restrictor kit is also available from Moroso.
Ford D0AE Cleveland rods are...
Ford D0AE Cleveland rods are good for up to 400 hp if shot-peened and fitted with ARP bolts. All 351C builds must be dynamic balanced to prevent vibration and free up power.
Main bearings in the 351C...
Main bearings in the 351C are smaller than the 351W. The logic is less friction. Oil comes from a common galley that feeds the cam and lifters. We improve oil flow to the mains by controlling flow to the cam and lifters.
Clevelands are clearly different...
Clevelands are clearly different from their 289/302/351W counterparts due to canted-valve cylinder heads. Canted or poly-angle valves change the location of piston valve reliefs entirely, which makes these pistons compatible only with Cleveland cylinder heads. Note valve relief positioning at 8 and 2 o'clock, as well as cylinder notching for additional valve clearance.