Hey guys, the long post below is my reply to a series of negative comments regarding the 351C on another forum. The 351C has received a lot of negative opinion from within the Pantera hobby over the years. Although I've only scratched the surface, I thought you might find the the brief insight into the 351C's design I provided informative. Enjoy.
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Ford's literature says the 351C 4V's reason for being was (1) racing (2) a performance option for production cars (3) cost.
Its a racing motor. It was designed for 6 liter NASCAR racing, banging fenders with cars powered by 426 Hemis & Boss 429s. Let that soak in for a moment.
It was designed by the same guys who designed the 427 FE. The 427 FE featured a steel crank, thick bulk heads above the main bearings, cross-bolted main bearing caps, a main priority oil passage running down the side of the block. These engineers found those features necessary for the 427 FE to survive NASCAR racing.
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 motor didn't need those features, or they were up to something new with the 351C 4V. Something very deliberate. The 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.
I will admit that the lubrication system (comprised of only two oil passages) and the thin cylinder walls must have been budgetary compromises. I must also point out that some (not all) NASCAR teams, and some (not all) big name drag racing teams had access to heavy wall blocks (Bud Moore's blocks) and fully counter-weighted steel cranks (Moldex cranks). But more often than not, race teams went racing with production parts.
The 351C 4V benefited from the new ways of doing things the engineers had learned while designing racing motors such as the Indy racing motors of 1963 - 1965. Design of the Cosworth DFV Formula One motor was also wrapping up in England in 1966. The 427 powered Ford GT40 was dominating LeMans and the World Endurance Racing series in 1966. When design of the 351C 4V began in 1966 Bill Gays engine group was literally immersed in applying high technology in the design of racing engines. Ford literature from the era described the Cleveland as "an engine that reflects the racing heritage of Ford products on the worlds toughest race courses". To achieve the goal of building a potent and durable racing motor that could be mass produced as inexpensively as possible the team relied upon the use of engineered solutions, intelligent design and finesse rather than the expensive, heavy, brute force solutions that had been applied in the past when building Fords 427 FE of the mid 1960s.
One example of solving problems with finesse rather than brute force is the extra wide footprint of the 351C main bearing caps. The footprint gives them great stability without resorting to using cross-bolts. And it makes the 351C 4V less expensive to build along the way.
When the 351C 4V entered the scene in 1972, NASCAR was dominated by 7 liter endurance racing motors than cruised around the ovals at about 7000 rpm making over 500 bhp. Endurance camshafts of the day had about 0.600 inch lift.
It was no accident that when equipped with a 0.600 inch lift endurance racing camshaft the 351C 4V makes about 515 bhp at about 7000 rpm. From 5.75 liters! 7 liter hemi motor torque and horsepower from 5.75 liters at the same rpm.
Let that very deliberate fact soak in for a moment.
The engineers hit their mark dead on. No mistakes. No getting lucky. It was all very deliberate. The Cleveland is a very damn amazing racing motor. It just lacks the curb appeal of the hemi motors with their big aluminum heads & centrally located spark plugs.
There's a reason why even today its hard for modern alloy heads to improve upon the intake port flow numbers at 0.600 inch lift achievable with the iron 351C 4V head. That intake port was deliberately optimized for 0.600 inch valve lift. Some people have ignorantly referred to the intake ports of the 351C 4V as nothing more than big pipes for gulping air, inferring there was no intelligent engineering in the design. This is, of course, far from the truth. Ford literature from that era described the ports as “carefully sized”. The cross sectional area of the 4V intake port (3.14 square inches at the push rods) had been used in high performance FE engines since 1960; displacing 352, 390, 406, 427 and 428 cubic inches.
As the 351C 4V powered Fords thundered around the banked ovals at 7200 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, and in spite of their lack of cross bolting. The engineers achieved the 351C 4V'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 motor reliable. The 351C did not have a reputation for problems in the early years, excepting for under-lubricated rod bearings above 7000 rpm. Through 1973 all the press the 351C 4V received was "mostly" stellar.
1974 was the first year the 351C received bad press in the magazines. It was the year of the first oil embargo. It was the year everyone started buying intake manifolds with tiny runners, economy cams and headers with tiny primaries trying to improve the fuel economy of their V8s. It was the year that the sbc with its small ports began to dominate the aftermarket parts industry, helped along by a bunch of guys like Vizard & Yunick with vested interests in the little sbc motor. A magazine writer named CJ Baker was a significant source for the body of mis-information that grew up around the 351C 4V.
As is usual in motor sports, racers & teams kept pushing the limits. They were no longer satisfied racing at 7200 rpm and they began pushing the motors to higher and higher engine speeds. By 1977 they were cruising the ovals at 8500 rpm and admitted to making 570 horsepower. Quite a bit above the original design parameters of the 351C 4V. The problem was, US Ford abandoned racing in February 1973, and no further official development of the motor occurred after that.
Hank The Crank introduced a forged steel 351C 4V crankshaft in 1974. The crank was internally balanced, and fully counter weighted (8 counter weights). The additional counter weights were needed for racing above 7500 rpm. The crank also had relocated oil passages, which may hint at the possibility that the oil passages in the oem crank were suspected of being problematic.
Shortly after the introduction of the HTC steel crank the engineers at Ford authorized the manufacture of a thick cylinder wall & thick bulk head block in Australia. By the 1976 NASCAR season all Ford teams had access to fully counter-weighted steel cranks, and blocks with thick cylinder walls and thick main bearing bulkheads, ala the 427 FE. It's not unreasonable to assume the 8500 rpm engine speeds required these changes ... but iron has dampening properties that steel does not. There's equal evidence the steel crank necessitated the heavy duty block.
The HTC crankshaft was an aftermarket part. How many of us have had problems with our motors caused by aftermarket parts? Did the steel crank negated the engineering that went into the block? The nodular iron crank and the thin wall block were engineered to work together as a durable system.
So one person observes the design of the 351C and concludes the short block is nothing special, the castings are thin and flimsy and the head design is compromised. When I observe the 351C I conclude it is an AMAZING racing motor designed by a group of brilliant men. When the original castings are carefully assembled it is capable of making 500 bhp naturally aspirated at engine speeds up to 7200 rpm under NASCAR racing conditions (some of the toughest racing in the world) for a very long time.
-George
