05/30/2025
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427 Pre-Chamber
Engine no. AX626-414-1-15
Built from a Ford 400, Ford had BIG plans for this engine upon its debut in 1971 that most people don't know about.
The 400 is part of the 335-series Cleveland engine family and is a tall deck height version of the 351C engine. When the 351 Cleveland debuted, it was no secret that it was bred for performance. By 1971 the 400 had debuted to fulfill mid size engine needs in vehicles but not without a secret. The engine was headed in the direction of being the direct successor to the Cleveland in the performance department and Ford actually made a few experimental factory four barrel intakes. Early blocks had thick webbing for 4 bolt mains and were stamped for dual bellhousings. The deck height was increased to 10.2 to accommodate the longer stroke and the larger 385-series bellhousing as the power levels they were going for could not be supported by the transmisslons in that small bellhousing they had avallable at the time because the 400 had one if the longest strokes of any Ford passenger engine, even longer than a 428CJ. Torque was comparable to a 460 and at a lower rpm. Early engines had 9.2:1 compression. Unfortunately Ford was forced to choke the daylights out of it for sake of satisfying the government. Due to this, the engine never got its due as planned. In 1975, the USEPA mandated catalytic converters and unleaded fuel. With the low octane of unleaded gasoline, and no unleaded premium available for a few years, Ford had to make drastic changes to the 400. To avoid detonation problems, Ford introduced a lower-compression piston with a 15 cc dish, and specified static ignition timing at just 4 degrees BTDC, causing advertised horsepower to drop.
Just to clarify, there is no 400M and there is no 351M/400, it is one or the other. The engine was produced from 1971-1982, with the 400 coming first. The 351M came out in 1975, with the "M" standing for "Modified" as it was "modified" from the 400 which has 3" main bearing (same as a 351 Windsor). The 351M was produced at both the Cleveland foundry and Midland, Michigan casting center.
By the mid 70s, after Fords total performance era started to dwindle down, Ford started really playing with the 400 in prototype form that never was released to the public. Before the 351M was released, there were 50 427ci water injected, 3-valve, pre-chamber engines built out of 400 architecture. Ford at this polnt was deep into R&D with the 400 for not only emissions but power. This engine did not have exhaust ports, Instead the intake manifold had crossover ports built into the manifold next to the intake runners, with a large single dump above the bellhousing. The next step was moving the oil port for the pressure sending unit as it was in the way. The large single port was designed to have either a single or dual turbos directly mounted off to the sldes above the valve covers or to the sides of the heads. With water injection the engine was designed to operated at around 320°.
This was effectively a 5-stroke engine. Starting with the compression stroke this and the next two strokes were the same as a conventional 4-stroke engine: Compression, Ignition-Power and Exhaust. Difference was that a small jet of distilled water would be sprayed onto the top of the hot piston, which would turn to steam and act as a power-assist while also bringing in a fuel-air mixture during the intake stroke, increasing the engines fuel efficiency by 25%. To date we have not been able to find any test results or public records about this motor.
The engine also was in development at the same time with another 400 that used a bell driven mechanical fuel injection pump and direct injection during Fords PROCO development program, starting in 1971. Unfortunately that engine never totally came to fruition either, and the project was dropped. (We covered that engine back in March of this year.)
Ford had the turbos and other experimental plumbing removed, and this is what's left. Only a few Pre-Chamber engines stll exist and are currently owned by collectors and are in good hands as Ford ordered them to be destroyed, these are the few that snuck out.
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