While the M family was born with a chain-driven single camshaft it evolved into a belt-driven DOHC system after 1980.

The M-E variant, available only in the Japanese domestic market, was the first Toyota engine to be equipped with fuel injection (around the same time as the 4-cylinder 18R-E).

They were commonly found on the large Toyota Crown, Mark II, and Supra models.

Output was 110–115 PS (108–113 bhp; 81–85 kW) at 5,200 to 5600 rpm, depending on specifications and model year.

The "M-C" engine, for commercial vehicles such as the Crown Van produces 105 PS (104 bhp; 77 kW).

[1] Twin sidedraft SU Carburettors pushed output for the M-B and M-D to 125 PS (123 bhp; 92 kW) at 5,800 rpm.

[2] Anti emissions versions, the M-U and M-EU, replaced the M and M-E on the Japanese market in mid 1976.

The emissions system was called TTC (Toyota Total Clean), with a "-C" to denote the installation of a catalytic converter.

The earliest models were simply called the M-LPG, with the emissions scrubbed M-PU replacing it in mid-1976.

The M-E fuel injected induction system appeared in the 1973–1976 Toyota Mark II (X10) "LG" sedan and hardtop as sold in Japan.

The M-E was redesignated as the M-EU for the Japanese market in December 1976 when it received the TTC-C (Toyota Total Clean), catalytic converter to meet anti-emissions laws.

Another 1,988 cc (2.0 L; 121.3 cu in) naturally aspirated inline 6, with both squared bore and stroke of 75 mm (2.95 in) and equipped with 3 Mikuni-Solex 40 PHH carburetors, the 2 valves per cylinder DOHC 3M, was produced from 1966 through 1971.

In Europe (aside from Sweden and Switzerland, who received the same spec engine as Australia) the 5M-E produced 145 PS (143 bhp; 107 kW) in the Crown MS112 and the Celica Supra MA61.

It was quite different from any previous member of the M family, with Bosch L-Jetronic-derived electronic fuel-injection (using an AFM intake measuring scheme), wide-angle valves, and belt-driven dual camshafts.

The newer engine control system found in these later cars was named TCCS, or Toyota Computer Control System and, together with different intake runners, increased max power by 5 PS (5 bhp; 4 kW) from August 1983.

The 6M-GEU is usually the lower powered variant of 6M engines, due to more restrictive exhaust and increased emissions-control hardware.

The Toyota 7M-GE introduced in the early months of 1986 is a 2,954 cc (3.0 L) 24-valve (4 valves per cylinder) DOHC/fuel-injected engine.