Toyota 7M engine

The Toyota 7M engine, first released in 1986, is the final evolutionary step of the M series engine, which originally debuted in 1965. They were installed in the Toyota Supra, Toyota Soarer and the Toyota Cressida. All 7M engines use a DOHC valvetrain (solid shim-over-bucket lifters), with valves spaced at a performance-oriented 50° angle. Both camshafts are driven by a single cambelt from the crankshaft. Three derivatives exist; the 7M-GE, 7M-GTE and a 7M-GTEU. The 7M was finally discontinued in 1992, supplanted by the JZ series engines in all applications.

7M-GE
Originally released in the new MkIII Toyota Supra (A70 Chassis) midway through 1986, the engine remained largely unchanged throughout it's 6 year lifespan. It used Toyota's improved TCCS EFI system, using a flapper style airflow meter and a distributor. Power was fed to the wheels via either the W58 Manual transmission used in the previous MkII Toyota Supra (A60 Chassis) or an A340E 4-speed Automatic.

7M-GTE
Introduced in 1987, the 7M-GTE block differed from its normally aspirated brother by its lower compression pistons, and included oil squirters in the block to cool the underside of the pistons, due to the increased combustion temperatures. The intake cam also differed from the 7M-GE, although the exhaust cam remained the same. A single CT-26 turbocharger was installed, and set from 4.8 to 7psi (dependant on the fitment of either an R154 Manual transmission or toughened A340E Automatic transmission). Management wise, it also used TCCS, but instead of a flapper style airflow meter, it used a Karmann Vortex style airflow meter. Likewise, instead of a distributor, a camshaft position sensor and three wasted spark ignition coils were installed.

7M-GTEU
This was a special run of the 7M, intended solely for the MkIII Toyota Supra Turbo-A in late 1988. A customised CT-26 turbocharger was installed, different inlet & exhaust camshafts with 10 degrees more duration and marginally more lift. The management was altered again, so rather than either the flapper style airflow meter, or Karmann Vortex airflow meter, the ECU sensed manifold pressure instead. All other specifications remained unchanged from the 7M-GTE.

Criticisms
The 7M's have a reputation for being especially unforgiving when it comes to maintenance schedules, and oil changes. Although the sump is baffled, often, if the oil level is lower than the maximum mark on the dipstick, oil starvation can occur under heavy cornering, acceleration or braking, leading to a drastic reduction in engine bearing life, usually resulting in a spun bearing. Regular oil changes with good quality 5w30 oil, and overfilling by 1 quart (0.9 litres) helps to reduce this occurrence.

Likewise, all 7M's are susceptible to a blown head gasket, due mainly to the torque specifications of the cylinder head bolts. Originally, the design team intended to use an Asbestos gasket, however, this was quickly changed to a composite gasket due to regulations concerning the use of Asbestos being implemented worldwide. However, despite the change in materials, the original torque specification of 58 lb/ft remained unchanged. A simple fix to the solution is to change the headgasket, preferably with a high-quality Toyota replacement one, and torque the head bolts to 72 lb/ft. For further piece of mind, rather than using OEM headbolts, ARP Head Studs can be used, torqued to 78 lb/ft.

The grade of aluminium used in the 7M's 24v Cylinder heads is also regarded as substandard, as they're prone to annealing after being overheated. As a result, exhaust studs are at risk of stripping the threads in the head, due to the fine pitch angle used (M10x1.25). Again - this can be rectified by drilling the threads and inserting helicoils