5.8 Liter V8: Understanding The Ford 351 Engine Mysteries

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It is easy to get the Ford 351 V8 engines confused, but the 5.8 liters powered almost everything in the Ford lineup over thirty years from the late 60s-90s.

Ford made the 5.8L (351 ci) eight-cylinder engine in three different versions. In the late sixties, Ford developed the 351W (Windsor) as a stroked engine from the 302. The 351C (Cleveland) and 351M (Michigan or Modified) were part of the 335 family of engines and used in various models for years.

The Ford 5.8L V8 has a legacy of reliability and performance for many classic Ford vehicles. Beginning in the late sixties and stretching nearly three decades before being retired, the 351s helped power almost every Ford model. While Ford tried to help identify the separate engines by sticking an initial on them (either W, C, or M) to indicate their place of origin, it can still be confusing to try and keep them straight. (If you have ever bought the wrong part for a 351, you know exactly what we mean). Despite their identical displacements, the 351s are not the same engine. Yet, each engine served its purpose, helping power Ford to new heights during difficult times. Let's take a closer look at the 351W (Windsor), 351C (Cleveland), and the 351M (Modified) to see if we can learn their mysteries.

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The 351 Windsor V8

With ever-increasing competition from both GM and Mopar, Ford needed a way to boost the performance of its 289/302 V8 family of engines during the late sixties. While the 302 had been introduced just a year before (1968), it had served them well, replacing the half-decade 289. Still, the Blue Oval couldn’t help but feel that it needed more. The Ford engineers decided that one easy way to increase performance and power might be to take an existing engine, give it an increased stroke, raise the deck height, and reinforce it where needed. The new motor would need a revised cast iron engine block to accommodate the increased stroke. However, it could use the same cylinder heads and other minor parts (saving production costs) while still achieving the kind of performance Ford owners demanded. The new engine got its name “Windsor” from the plant's location, namely, Windsor, Ontario.

While the new motor would use many of the same minor components as had been in place on the 289/302, including bore size, motor mounts, and other items, the engineers raised the deck height to accommodate the increased stroke of 3.5 inches. The firing order was changed to reduce the noise that had plagued the 289/302 engine. Large main bearing caps, longer connecting rods, a more robust oil pump, and a repositioned water pump were added to improve performance. Ford recast the block to accommodate the increased torque that the engine would produce, strengthening it so well that it became the sought-after component for performance junkies for years.

The 5.8L engine was designed to provide better performance for the 1969 model year and was offered in the brand-new Mach 1. Even though Ford introduced five new Mustangs for the year, the new fastback was positioned between the GT and the Shelby Mustangs in the lineup. Ford offered the 351 V8 as the standard engine with a choice of single 2 bbl or 4 bbl carburetion. Early sales brochures indicated that the 351W produced 250 horsepower with a 2 bbl carb and a 9.5:1 compression ratio (290 hp with the four-barrel setup with a 10.7:1 compression). Owners could choose large displacement V8s, like the 390 or 428s, but nearly half of the Mach 1s produced contained the standard 5.8L 351 motor.

It would not be long before Ford used the engine in other vehicles, from Mustangs, Cougars, Station wagons, Ford trucks, and marine applications. The Windsor plant produced over 8.6 million 351W 5.8 liter V8 units during its twenty-five-year run until 1996. Over the years, Ford continued to use the Ford 5.8 liter V8, tweaking it as fuel economy standards became more paramount.

The 351 Cleveland V8

Ford Motor Company felt that the demand for the 351W engine would be more than the Canadian plant’s capacity, so the decision was made to enlist another plant to handle the overflow. Ford picked the Cleveland, Ohio plant but at the same time wanted to make modifications to the 5.8 liter V8 to further enhance its performance. The tinkering resulted in the 351C V8 morphed into a different small block engine than its Windsor counterpart.

The goal for the 351C was to produce a reliable V8 that could be easily upgraded when the time came. Using the 385 Big Block engine as inspiration, the 335 family used free-flowing canted-valve cylinder heads to allow for large intake and exhaust valves, improved piston rings, push rods, and a modified oiling scheme to keep production costs down.

While the 351C has the same cylinder bore and stroke as its Windsor counterpart, the 335 family of engines has a two-inch extension cast onto the front of the engine for an integrated timing cover. (The best way to tell the difference between the 351C and 351W is to look at the water pump. The 351C has an incorporated water pump in the engine block. The 351W does not).

The result of the additional casting was that the 351C sits lower in the engine bay (which makes it the perfect muscle car engine to upgrade). The engine is heavier than its Windsor cousin (25 lbs). Additional upgrades included a dry aluminum intake manifold casting (351W uses a wet intake) and different-style combustion chambers with smaller spark plugs. Ford was so impressed with its performance that it wasn’t long before they upgraded it to see what the 351C could do.

The 351C was introduced for the 1970 model year Mustang, offering two versions. The conventional 2 bbl carburetor produced 250 hp, while the high-performance version topped at 300 hp. Ford tweaked the engine by developing an H-code variant in 1970, and the Boss 351 R-code produced 330 hp the following year. Torque ratios hovered around 380 lb-ft for the duration of the production run. With an 11.0:1 compression ratio, the new Mustang engine blistered down the track in 6.6 seconds 0 - 60 and a 15.1 quarter mile @ 98 mph.

While the 351C would not last nearly as long as the Windsor motor, it served Ford’s purpose during the muscle car era, and restorers can still find excellent versions to purchase as a crate engine.

The 351 Modified V8

Ford discontinued the 351C engine in 1974 but found itself still needing an engine that could fit into large passenger cars, achieve ever-increasing fuel economy and emission standards, and not cost a fortune to build. Once again, Ford looked at how it could modify the 335 family of engines to produce the results that it needed.

Ford developed the 400 ci V8 with a taller deck, more extensive main journals, and longer stroke but used many of the internals of the 351C. When the company discontinued the Big Block FE engines in 1975, Ford “modified” the 400 down with a shorter stroke to produce the 351 displacement. (Early versions shared the same block as the 400, which led to severe problems).  Ford named the new engine the 351M and began producing it at the Michigan casting and Cleveland foundry. (The fact that the engine was cast in Michigan has some owners thinking the “M” stands for Michigan).

Ford first used the 351M in passenger vehicles, with later applications moving into trucks and SUVs. The 5.8 liter V8 has an 8.0:1 compression ratio, which was less than ideal but contributed to better fuel mileage. The 351M was never designed to be a performance engine, with most versions of the motor producing only 150 hp and around 250 lb-ft of torque.

Ford utilized the engine until the early eighties for trucks, but after 1982, they stopped using the motor completely.  As mentioned, the 351M engine developed issues with water jackets leaking and cracked blocks, and after its use, Ford would not make another push-rod V8 until 2021.

While the engine could never be considered a Ford elite powerplant, it served its purpose, getting the Blue Oval through the complex seventies, when consumers were distancing themselves from gas-guzzling motors that robbed their wallets.