Ford 335 Engine - 400

400

The mid block FE engine family was getting outdated, and the big-block 385 family could not meet the efficiency requirements of the time. At the same time, the small-block Windsor engines were too small and high-revving for Ford's fullsize car and truck applications. So the company developed a new small-block to meet the desired levels of economy while still providing the kind of big-block torque that was needed to move 2+ ton vehicles.

The Ford 400 engine was based on the 351 Cleveland but was produced with a taller deck height of 10.297 inches compared to the 351C's 9.206 inches. This allowed for a longer stroke while retaining the 351C's rod-stroke ratio. These blocks also share the same oiling route in the block. The 400 featured larger (Windsor sized 3.00 inch with Cleveland cap register) main-bearing journals and had "square" proportions, with a 4.0 in (102 mm) bore and stroke; it therefore displaced 402 cu in (6.6 L), making it the largest displacement small-block V8 made at that time. It was introduced in model year 1971 with a half-inch (12.7 mm) longer stroke than the 351 Cleveland, making it the longest-stroke Ford pushrod V8 engine. A long-stroke engine has good low-end torque. This was a good compromise given Ford's requirement for an engine to power heavier mid-size and full-size cars and light trucks. The M-block, as it became known, was the last pushrod V8 block designed by Ford. The M-block also shares some elements with the Windsor engine family: bore spacing, cylinder head bolt-patterns and crankshaft journal dimensions.

The 400 was seen as a smaller and lighter replacement for the big Ford 385 engines, the 429 and 460, in Ford's larger cars. Weighing just 80% of a similar big-block, it was originally available in Ford's Custom, Galaxie and LTD lines, and in Mercury Monterey, Marquis, and Brougham. Later, it would power the Ford Thunderbird, the Lincoln Continental, Mark V, mid-size Fords and Mercurys, and Ford light-duty trucks.

Most 400 blocks use the same bellhousing bolt pattern as the 385 family big-block to make it compatible with the higher torque-capacity C6 transmission used on the large cars and trucks. There were a small number of 400 block castings that used dual bellhousing patterns for mounting an FMX transmission. The 400 was modified in 1975 to use unleaded gasoline.