The Burden of a Bad Reputation

It’s unfortunate that a bad reputation is so easy to gain but so tough to lose. As true as that statement is for people, it’s also the case when it comes to certain vehicles and engines. Ford fans will always have a soft spot in their blue-oval hearts for the Windsor, the Cleveland and the big 460 FE engines—and deservedly so. If you’ve ever crawled a junkyard for one of these engines, you’ve likely passed over more than a few 351M and 400 engines to find what you are looking for. Poor factory numbers and bad word-of-mouth have made these cousins to the mighty Cleveland about as wanted as poison ivy at a nudist colony, but there is power to be found in those engines—and cheap, too.

The Introduction of the 400 Engine

Ford introduced the 400 engine in 1971 models as a replacement for the company’s aging big-block designs. The change was necessary to reduce emissions and increase fuel mileage to meet government mandates. Ford needed a more efficient, lighter engine capable of big torque to be used in big cars and light trucks. The block design was new but not revolutionary; it was based on the successful 351 Cleveland design, but with more deck height (1.09 inches) to accommodate a longer 4.00-inch stroke (compared to the Cleveland’s 3.5 inches). Combined with the 4.00-inch bore, final displacement was a healthy 400 cubic inches.

Birth of the 351M: A Modified Cleveland

Even stricter regulations in 1975 led to the demise of the Cleveland engine and the birth of the 351M. Although it doesn’t really stand for anything, most engine builders refer to the 351M engine as a “Modified” because it is essentially a de-stroked 400. The only practical differences from the 400 to the new 351M were a crank with a shorter stroke (3.50 inches) and a new piston with a greater compression height to keep the compression ratio up. Because both engines shared so much with the Cleveland engine, they were given the same “335” engine series designation.

Challenges of the 351M and 400 Engines

Smaller V8 engines were becoming more popular in both cars and light trucks, and the 351M was introduced as a way for Ford to supplement the Windsor engine in order to meet overall demand. The many common parts it shared with the 400 made the 351M relatively inexpensive to produce, but Ford never really had a chance to show off its true potential. Efforts to make the engine perform well with catalytic converters, EGR valves, and unleaded fuel meant that the engine wound up with a small camshaft that was retarded from the factory a power-killing six degrees and a low compression ratio. Later in the engine’s life, the 351M was choked down to the point that it could produce only 152 horsepower, while the 400 was worth only 160.

Reputation vs. Reality: Unlocking the Potential

Fortunately, the 351M and 400 engines can be made into quite capable engines. Since they were sold in many different Ford cars and trucks between 1971 and 1982, they are plentiful in the junkyards, and because of their reputations they can often be had quite cheap. We got ours, in fact, for free. It was in a 1978 Bronco, and the owner required only that we tow the entire vehicle off his property.

Strategies for Building a Torque Monster

The trick with the 351M is not to try to make it into something it isn’t. Since it shares so much of its architecture with the 400, it only makes sense to stroke the engine with a new crank and pistons to get those extra 50 cc’s of displacement. The long 4.00-inch stroke makes this engine capable of producing plenty of torque, and the horsepower can be significantly improved as well.

A Budget-Friendly Approach to Performance

When we began the rebuild of our 351M the goal was to double the pathetic 152 advertised horsepower, produce over 400 lb/ft of torque and do it as reasonably as possible on the checkbook. That means no exotic parts or power-adders. Our major aftermarket parts included only an Edelbrock carb and intake, a camshaft and rocker arms from Comp Cams and a new ignition from MSD. Everything else is almost completely stock or stock replacement. The result is a torque-monster with even more stump-pulling power than we had hoped, and it all can be built by the average gear head.