The first M engine was produced from 1965 through 1988 at 2.0 liters, single overhead cam, chain driven producing around 110bhp.
Also in 1965, a prototype 2000GT was unveiled, powered by what would be known as the 3M. It was the same 2.0 liter M block, but was the first inline 6 to have used a Yamaha dual overhead camshaft cylinder head.
The M-TEU (turbo), 2M and 4M remained single overhead cam, and were used in several vehicle applications over a couple of decades.
In 1967 the M block was increased in displacement by stroking to 2.3 liters, the 115bhp 2M. This engine's crankshaft is what will power all M block engines larger than 2.0 liters until the 6MGE in late 1984.
In 1972 the M block was upgraded again, bored out to 2.6 liters to create the 122bhp 4M which was at first carburated, but became EFI (4M-E) in 1978 where horsepower fell back to 110bhp but with increased gas mileage most likely due to the global oil crisis.
In 1980, the M block was once again bored out, this time to 2.8 liters in the creation of the still single overhead cam and initially carburated engine, the 114bhp 5M. A 116bhp EFI variant (5M-E) was produced for North America, but Australia and Europe got a 138bhp engine most likely due to leaded fuel.
In 1981, Yamaha once again got with Toyota to produce a dual overhead cam engine for the 1982 model year, the 5MGE. Initially, the engine produced 145bhp in North America with the 8.8:1 compression ratio, but power increased over time to 161bhp with a better engine control system, better intake runner shape and higher 9.2:1 compression. In Europe, these engines are claimed to produce around 178bhp due to not having a smog system, and having entirely different camshafts with an ECU/AFM tuned to those cams.
There were aftermarket piston kits (85mm) that took the 5MGE up to 2.9 liters for around a rumored 230bhp. There was also supposedly a forged crankshaft kit (91mm stroke versus 85mm) that would bring the engine to 3.1 liters, along with the piston kit for a again, supposedly, 250bhp. There is little to no documentation of these Kuwahara 3100 kits or engines other than "word of mouth" and some typed words on this website and this website. If anyone would care to share legit information about these racing boat engines and kits, please email me at thesupragoddess@aol.com
In late 1984, the M block was yet again increased in displacement to 3.0 liters from a 91mm stroke to create the 6MGE engine. Unfortunately, this engine never made it to any North American cars, as it was reserved only for the MS125 Crown and MZ12 Soarer. For the Soarer the engine output was around 170-175bhp with the standard flapper-style AFM like the MA60 Supras have. The Crown, however, was occasionally fitted with a Karman Vortex type AFM, where these 6MGEs had an output of around 190bhp. These engines ran in cars until 1987 before the next, and last, generation of M engine would take over.
Early 1986 saw the introduction of the first and only 4 valve per cylinder M engine. The 7MGE was produced from 1986.5 to 1992 producing 190bhp to 204bhp. The 24 valve engine got boost in 1987 and it's output was around 232bhp with a factory intercooled system.
After 27 years of production and over 30 years of development, the M engine was put to rest in favor of introducing the now legendary 1JZ and 2JZ engines.
RIP M Engine 1965-1992
