The 351 Cleveland story is one of the most befuddling in Ford history. In North America, it was only in production for four years (1970-74), yet it became the hotrodder’s mainstay in Australia well into the 1980s. In fact, the 351C has been as popular in Australia as the small block Chevy, which has significant meaning when you consider the legendary Chevy’s great success for approaching 70 years.
Ford’s 335 Series “Cleveland” existed in two forms in North America—the low deck 351C and the raised deck 400 and 351M. When you look at the two types side by side, the difference in size is quite clear. Enthusiasts get this mixed up all the time, but there is but one truth. The 351C and both the 351M and 400 are not the same engines. They are different beginning with the block and its internals.
The 351C arrived in 1970. The 400 showed up the following year in 1971 to replace the FE Series 390 and 428ci big-blocks in full sized Fords and Mercs. The 400 was a “square” engine meaning it had the exact same bore and stroke—4.000 inches by 4.000 inches.
It was an engine long on growth potential, but never grew any larger. Ford could have grown the 400 to 435 to 450 cubic inches with less weight than a big block. However, there was also the new 429 and 460 cubic inch Ford 385 Series big blocks, which didn’t weigh much more that had this displacement range covered.
In fact, Ford planned 500+ cubic-inches for the big block, which never materialized amid environmental concerns and the Arab Oil Embargo.
The 400 saw steady use in passenger cars through the late 1970s. In 1975, Ford dropped the low deck 351C in North America, instead de-stroking the 400 to 351 cubic inches and calling it the 351M.
By the way, the 400 was never called the “400M” by Ford. It was just the 400. The “351M” designation differentiated the 351C from the raised deck 351M. The 351C and 351M are not the same engine, by the way. In fact, if you have a 351M, you might as well stroke it to 400 cubic inches because both the 351M and 400 employ the same block and roughly the same weight. The 351M was used extensively in Ford and Mercury passenger cars. It also found use in Ford F-Series trucks in 1977-82.
What makes the 351M and 400 different than the 351C is larger main and rod journal sizing along with the raised deck block. The 351C has a 9.206-inch deck height. The 351M and 400 have a taller deck at 10.297 inches. Cleveland crankshafts all look the same, however, they are different. The 4M crank has a 3.500-inch stroke and a 2.750-inch main journal. The 400 crank has a larger 3.000-inch main journal and a 5M stamp. The 351C, 400, and 351M crankshaft identification is “4M” for the 351C and “5M” for the 400. Expect to see “1K” for 351M. Though you see 4MA, 4MAB, 5MA, 5MAB, the additional “A” or “B” is nothing more than an engineering revision to the casting. The Cleveland engines were never factory equipped with a steel crank.
Understanding how to build power into a Cleveland boils down to knowing how to choose the right cylinder head for these engines. Ford North America never got its act together on 351C cylinder heads. The 351C-4V head had terrific wedge chambers with good quench, yet with ports too large for street use. The 2V head had right sized ports, yet big open chambers with poor quench prone to detonation and hard starting. Some stubbornly stand by these open-chamber heads, however, they’re a poor choice. Ford added insult to injury with the 1973-74 4V head with huge ports and the 2V’s open chambers to get compression down. Instead of controlling compression with a dished piston, Ford made the chambers large like an indoor football domed stadium.
The 400 used the same cylinder heads as the 351C-2V with the same open chambers and smaller “torque friendly” port sizing. Detonation issues drove car owners crazy with these heads. It was the 400’s stroke that yielded the torque.
I’ve been Ford loyalist for decades. I love Ford for its history as a company along with its products. However, I will never understand Ford for its port sizing. Ports were either too small or outrageously large. The 351C is one of the best examples we can think of. The 351C-4V cylinder heads were great high rpm heads with their drive-through ports, which are happiest at 7,000 rpm, but frustrating on the street because they deliver poor low-to-mid-range torque for the street.
Meanwhile, in Australia, Ford continued with great improvements in the 302 and 351C engines. Yes, Ford did a 302 cubic inch Cleveland with even smaller 54-57cc 4V wedge chambers with good quench. The Aussie Cleveland head employed all of the great benefits of a well thought out head—wedge chambers and the smaller 2V ports for a perfect combination of flow and quench.
If you’re building a stock-appearing 351C, but want better performance, this is the head you want (though they’re becoming more scarce all the time).
Summit Racing Performance Heads
Summit Racing offers you an abundance of great aftermarket 351C heads that are also available for the 400. Trick Flow Specialties, as one example, offers several different 351C/351M/400 cylinder head part numbers, which enables you to fine tune your cylinder head selection. You just have to decide which cylinder head is right for your application. Summit Racing can help. Trick Flow has the broadest selection of heads in the marketplace engineered specifically for the 335 Series Ford middle-blocks. The Speedmaster and Edelbrock lines offer a number of terrific cylinder heads for the Cleveland engine family.
We’re working with the late Marvin McAfee of MCE Engines in Los Angeles on a 351C he was building back in 2008. Marvin lost his battle with old age at 87 last year, but his legacy of great engines remains. This 351C was shipped to Marvin from the Midwest with its share of issues.
Marvin was out to get it right and safely returned.
Jim Smart is a veteran automotive journalist, technical editor, and historian with hundreds of how-to and feature articles to his credit. Jim's also an enthusiast, and has owned and restored many classic vehicles, including an impressive mix of vintage Ford Mustangs.