Taken from another post by
Bryson Kriz
7M-GE to GE/T Conversion By Bryson Kriz
1.1 Introduction:
My car started its life as a Naturally Aspirated MA70 Supra, with modest modifications. After researching possible ways to find power in the 7M engine, not many options were out there for the GE trim. With most of the basic bolt on’s, it was a fairly quick car, but still lacked power to keep up to newer and modified sports cars. Aggressive camshafts, headwork, and possibly some sort of injection would be needed to achieve this. After looking into it more, not many options were available that still kept my car a semi-daily driver. At the end of Fall 2002, my car’s temperature gauge started to rise and what not. After developing various problems (later on I discovered that my distributor was on its way out), I parked the car for the winter and started gathering parts to do a conversion. A headgasket and clutch later, I managed to produce a car that I can drive everyday and still put down over 325 horsepower at the crank with basic modifications. When you hear about someone converting their car from an N/A to a Turbo, there are a few different ways to approach this:
1. 7M-GE to 7M-GTE Engine swap – Involves swapping the entire engine with wiring harness, ECU, transmission occasionally, and other various parts into the GE body. Very common trend due to ease of swap, lack of custom fabrication, and costs. Recommend to users with low/moderate knowledge of the 7M engine and slightly higher knowledge of mechanics in general.
2. 7M-GE to 7M-GE/T with GTE electronics – This is what my project involves. Keeping the GE head and block, I transferred over all of the mechanical and electronic portions of the GTE. End product is basically a GTE with the GE block/head, resulting in higher compression. More customization can be done this way (oil lines, filter, cooler, piping, compression, etc) but involves more fabrication of parts and a much higher price tag. Recommended to users with moderate/high knowledge of 7M engine , slightly higher knowledge of mechanics in general, and a higher knowledge of custom fabrication.
3. 7M-GE to 7M-GE/T with GE electronics – This is the most cost effective setup out there for N/A drivers, though I do not recommend it. This involves transferring the mechanical parts such as the turbo and intercooler to the GE engine while keeping the electronics (AFM, Distributor, Injectors, ECU, etc) in place. It can be done with a relatively low knowledge of mechanics and the 7M engine, but do not expect this setup to last long. Without extensive tuning and fuel management, the idea of a daily driver is thrown out the window. Only recommended for the serious user (if so, you should not even be reading this
) or someone who likes to experiment (aka blow up) with engines. Minimal price tag in the short term, larger price tag in the long term.
After studying each option, I chose the 2nd choice due to the fact it was one of the most sensible options next to an entire engine swap, and gave me a bit more flexibility in this project, and mostly, something unique.
1.2 Gathering Parts
This can either turn out to be one of the most time consuming, or quickest parts of the project. The best is to find a 7M-GTE that’s developing BHG (Blown Head Gasket), or has some sort of damage to the rear end. Either way, don’t start with a car that has 200k miles on it and has failing parts. Each of these options gives you a relatively good engine with minimal damage for a low price. You may think the initial price of buying a parts car is too high, but after tracking down all the parts individually, it adds up. If you can’t find a parts car, look for parts that come from a reputable source. Someone claiming a great CT-26 turbo with fast and furious stickers on E-Bay with a zero feedback rating is probably something you should stay away from. Now is a good time to think about some of the possible goals for the car. 550cc injectors could be bought at this point to save yourself from finding used 440cc stock turbo injectors and so on. Due to the price tag of these aftermarket parts and the current price tag of the project, this might not be realistic. I started out with 440cc / stock AFM / stock intercooler with my project, due to a lack of funds at the time.
1.3 Parts list from the GTE engine
Here is a list of the parts you need to locate off of a 7M-GTE engine. Try and stick to the same year (87-88/89-92) for your parts. Some things such as the wiring harness and ECU need to be the same year/model to work as well. Safest way to avoid complications is just to find the same year parts for the major electronic pieces. Items with a year in front of them indicate these types of parts. 1989 is the year used for example:
· 1989 GTE 5spd ECU
· 1989 GTE 5spd Wiring Harness
· GTE CPS (cam position sensor)
· GTE Coil Pack
· GTE Igniter
· GTE AFM
· CT-26 Stock Turbo
· CT-26 O2 Housing/elbow
· Downpipe / exhaust system
· Oil Cooler
· Oil Cooler piping
· Intercooler
· Intercooler piping
· GTE Exhaust Manifold
· GTE O2 sensor
· GTE Fuel Pressure Relay
· GTE Boost pressure sensor
· (6) GTE 440cc injectors (1989 7M-GE fuel rail)
· BOV (blow off valve)
· Various Hoses/Clamps
· Oil filter housing
· GTE Tachometer electronics
1.4 Various parts list
After gathering the parts from the GTE engine, there are a few other various parts you should gather to save you complications for the long run. I will go into greater detail later.
· Toyota Thermostat
· W-58(N/A) or R154(Turbo) upgraded clutch
· Aftermarket or Resurfaced Flywheel (W-58 or R154)
· ARP Head Bolts
· Toyota Head Gasket or better
· Toyota intake / exhaust manifold gaskets for the GTE (depending on application)
· Toyota rubber coolant hoses
1.5 7M-GE Engine dismantle
With the parts in hand, you can finally park your Supra to go under the knife. Remove all the electronics on the car that have some sort of connection to the wiring harness. Other electronics already hooked into the body of the car (such as the windshield wiper motor etc) will work regardless. The wiring harness extends over through the firewall on the passengers side of the vehicle. Make sure you disconnect/remove the battery before attempting all of this. Removing the glove box allows easy access to the GE ECU. Remove various intake and exhaust components to view the naked head and block. Remove head for resurfacing and remove transmission for upgrade (R154 turbo transmission) or replacing the GE clutch. The head gasket will not last very long under boost conditions, along with the GE clutch. Learn from my mistakes and replace both during the dismantle process. Personally, if you are aiming under 400-450 RWTQ, the W-58 (N/A) transmission should be fine. Keep all of the bolts and various parts together, as you will never know when you might need them again. Replacing various coolant hoses and replacing the thermostat at the same time would be a wise decision. As always, clean all of the parts thoroughly, such as the radiator. Years of driving accumulates large amounts of dirt, leaves, and other foreign objects on the front of the radiator resulting in cooling problems.
1.6 Head and Block preparations
To start off, i'll give you a brief history of my prior experience with the 7M motor with higher compression under forced induction. With ARP head bolts torqued to 72 foot-pounds, and a brand new OEM Toyota Headgasket (some say redesigned, i would be skeptical about that) I believed the way to prevent headgaskets blowing would be to control detonation. So with enough fuel in hand, I went the route of the stock headgasket. The Head was milled by a local machine shop 6 thousandths of an inch, and the block was cleaned. By that, I mean that I removed all the old gasket material on the block. Within 1000 KM, my headgasket was blown again, with deformation around the intake side of the gasket even worse than prior. With further research, I came to a conclusion that even though I did control detonation, that the way the 7M motor is designed, specifically the different expanding and contracting rates of the aluminum head against the cast iron block, along with the design regarding cooling passages on the OEM headgaskets, that a inferior product such as the OEM headgasket cannot last under these boosted situations. Some have used the OEM headgasket with proper torque with success, but under a high compression application, I would suggest against it.
With my 2nd headgasket blown, and knowing I was just getting started at 300 horsepower, I soon realized that the OEM gasket would not be the way to go. By taking the head into a local machine shop again, this time shaving 5 thousandths of an inch off, the head was ready to be installed. But having some time on my hands, I purchased new valve stem seals, and replaced my old ones accordingly. If your engine has a lot of wear, or if you are slightly smoking oil out of your exhaust, I would suggest to change these as doing it with the head on is much more difficult. I also received a five angle valve job with reground valves at this time, for better airflow. On the 7M motor, they come stock with a somewhat three angle valve job, which is much better than most stock engines. For the average supra owner, if you are tight on cash, I would advise against this modification, unless you can do it yourself or a reputable shop will do this job for cheap.
When going for “more-than-stock” power, there is no substitute for a properly installed Metal Headgasket. A few companies make these gaskets for the 7M, specifically GReddy and HKS. These headgaskets are of a much better design, regarding cooling passages, and come in various thicknesses. Unless you are confident with your judgment, order your headgasket after all of the block and headwork has been done. That way, you can select the right size to normalize or decrease your compression ratio. Remember, the higher the compression ratio, the more prone you are to detonation and pinging when running positive manifold pressure. Don’t expect to run 20psi on N/A compression and dodge extreme detonation.
For the block work, inspect the block for major crevasses in the block, paying close attention to the firerings around the cylinders, and damage around coolant passages. If it looks like the block is in decent shape, you can follow Reg Riemer’s guide to lapping your block at
http://www.supras.com/pub/SONIC/MA70/HKSMETALHGv5.txt , where you will find a more in depth guide to metal head gaskets, and their installation into the 7M. A common saying “an alarm system is only as good as it’s install” can be used here, as a Metal Headgasket will do you no good if installed incorrectly. Please follow these steps closely and do it once and for all for good. It’s not fun to replace blown headgaskets time and time again on your vehicle due to improper sealing. Ask me how I know.
