The 7 Series M engine was the last of the M blocks. The evolution from a 2000cc SOHC in-line 6 cylinder to a 3000cc DOHC 24 valve saw this engine family powering Toyota’s top of the line cars for over 30 years. Before retiring this series block Toyota saw it fit to crown the block with an impressive 24 valve head.
Following Toyota’s pattern of evolutionary engine development, the 7MG was a trouble free design- except for the cylinder head gasket problem. In both turbo and non-turbo varieties, the gaskets tend to start failing as early as 80,000. It does not matter wether the cars were either driven extremely hard or easy. Maximum mileage is from normally used engines, some of which survived to 150,000!
The bottom line is that these engines can survive all the horsepower you set it up for as long as you are aware of the maintenance requirement it needs (head gasket). Keep a fresh gasket on hand and it is capable of producing a lot of power.
The later model engines came with the Lexus style oil-filled mounts. The slight horsepower increase in the latter models came from computer tuning and exhaust differences. Internally they are identical.
In competition the 7MGT was handicapped by the heavy Supra body. Although it won numerous races- there was no major titles for this engine. Thanks to Japanese tuners (HKS, Greddy, Blitz) the street Toyota denizens ruled over the competitive models from other manufacturers. In it’s class and generation the 7MG was the engine. This same power potential led us to power older Supras, RWD Celicas, some pick-ups, even a cigarette boat- with these engines.
Modifying the 7MG / 7MGTE:
BLOCK: The block is trouble-free, but will not tolerate low oil conditions. It is a very robust bottom end that will survive mega horsepower engine build-ups. Since it is a long crankshaft, crack testing is mandatory between rebuilds. The con-rod small end should also be rebushed because they are subject to a lot of stress. Maximum bore should be limited to 85.5mm.
For normally aspirated engines compression can be raised to a maximum 12.5 compression, after which the dome design starts interfering with the combustion air-flow. For turbo set-up the compression can be set as low as 8.0:1. The original pistons did not benefit from later Toyota practice of piston coating, so for any major projects forged pistons are the only ticket.
Although the engine is able to rev high and the bottom end will survive high RPMs, heavy continuous boost conditions past 16psi will eventually warp the heads. Judicious use of boosts up to 30psi is not uncommon and survivable.
The block decks should be resurfaced to the best finish available. Invariably the head gasket will have gouged the surface. Make sure that the aluminum timing cover is on the block when the deck is surfaced, or else the head gasket will not seal properly. We send the blocks and head to a special grinding outfit- that machines aircraft components, and they are able to surface to a mirror finish. Upgrade all the engine assembly bolts. Replace all the hoses. Keep a spare head gasket.
CYLINDER HEAD: The 24 valve head is trouble free, but should be checked for warpage. There is a common propensity for the aluminum head to deteriorate around the water passages. Use the best anti-freeze you can get- more heads become unusable because of material erosion and decomposition- rather than cracking or warpage. The intake and exhaust ports can be cleaned up, but port and polishing is not mandatory- there are other pieces you can spend on that will return more horsepower for the budget.
Camshafts and adjustable gears are available to maximize the full potential of these 24 valve heads. Do not use cams over 280 degrees since the lower cylinder pressure will cause erratic inputs to the ECU. On the turbo models, the use of NA cams is an easy upgrade, if you can find them. In the cam journals to the head, there is a soft leadlike coating that is normally scoured. We have successfully polished of all coating into the bare journal and reused the cams with no problems.
The valve seals on some engines harden abnormally soon, sometimes even before the head gasket bows out. Replace the valve seals when you do a head gasket replacement. Again surfacing (like the block) to the best finish is mandatory. Use an aftermarket metal headgasket for maximum mileage in between teardowns.
FUEL SYSTEM: The stock fuel system for the NA and turbo models is adequate. For heavy turbo modifications please read the next section. The VPC designed for the 7MGT can also be used on the NA, an exclusive Toysport modification. This eliminates the air-flow meter and does wonders for throttle response and boost transition. For additional capacity there are 550cc injectors that will drop-in; use a JZA80 (Twin Turbo) fuel pump that is a direct replacement.
TURBO UPGRADE: The factory turbo is able to run boosts up to 14 psi (1 bar). Trying to boost above this is plain useless. In order of importance- the exhaust, intercooler, boost controller, ignition, fuel computer, turbo, vein pressure converter, injectors are the steps in upgrading. For anything over 14 psi a new block with forged pistons is necessary. Adjusting compression ratio for a non-turbo being upgraded to turbo, by the head gasket is not recommended.
The availability of metal head gaskets in various thickness and composition is more to compensate for the milling of the head and block, and slight adjustments in compression. There are 3 types of aftermarket metal headgaskets available- Stopper, Bead, and Grommet. The Stopper is a multi-layer set-up that will survive better than a factory gasket. The Bead has also multi-layer and is a more flexible and has a raised bead to help seal around the pistons. The Grommet has an additional seal ring, (like the factory units) and will take the most abuse.
The most usable turbo upgrade is based on the CT26 stock turbo. We were the first company to do this and maintain proprietary specifications. Some companies also do upgrades, but we are certain our set-up is the best. A twin turbo set-up is available, that makes the engine dramatically responsive and powerful- this is based on HKS TwinTurbo set-up on the old 5MG. There are numerous other single turbo set-ups, but they are not streetable.
IGNITION SYSTEM: The simplest most effective ignition upgrade for either NA or Turbo, are the HKS Twin Power (there are two different units). Do not even think of something else. The MSD or NGK wires also work very well as upgrades to factory wires.
Some Recommended Set-ups:
For stock configuration: The 7MGE/TE are common engines that reputable import shops, should be able to service. Machining engine components should be only trusted to known machine shops, since tolerance limits are crucial and very specific. Domestic machine shops, used to Detroit specifications, will not be able to properly service the requirements. There are several good overhauling gasket sets aside from factory- which are equal to the factory issue, but as a minimum use only factory original headgasket. Replacing the exhaust (on both models) produce instant power, the factory units "crimp" right under the axles- which the aftermarket units are able to maintain the full diameter.
For modified configuration: For normally aspirated models, mild cams, headers and a good exhaust produce expected results. To build a high compression model, stay within 12.5:1 compression (but you may need octane booster on really hot days. Do not expect to reach turbo power levels. For turbo models, re-read the Turbo Upgrade section. There were a lot of magazines that covered different set-ups- read between the lines. You will find that some articles contradict other articles! Enough said.
For racing configuration: Use the older Supra body, or remove everything bolted inside the car. More seriously- the engine is capable but the weight penalty does not make this vehicle competitive in all out racing. For milder competition like, Club Rallying or Road Racing- a properly set-up Turbo will be close to unbeatable, plus you will be cruising comfortably too.
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