11/02/98
Revision- 01/10/2001

SONIC TECH NOTE SERIES:

Preventative Maintenance Tech Notes 1987 to 1992 Supra MA-70 & 71 Series Non Turbo & Turbo v4.0

Information provided is given free of charge in good faith without prejudice

Table of Contents

   Section 1 7M-GE & GTE Engines
           1.0     Idling problems
           1.1     Head gaskets
           1.2     Valve Adjustment & Misc
           1.3     Cooling System
           1.4     Intercooler System {Turbo Only}
           1.5     ODD codes {knock Sensor Code}
           1.6     Oil pressure / 7M engines
           1.7     7M Cylinder Head Work and machining

   Section 2 Drive Train
           2.0     Transmission
           2.1     Drive Shafts
           2.2     Differential Carriers
           2.3     Front & Rear Wheel Bearings

   Section 3 Suspension
           3.0     Front Lower A Arms

   Section 4 Brakes
           4.0     Brake service

   _____________________________

Section 1 ~7M-GE & GTE Engines 1.0: Idling problems

    On a warm day, when restarting the engine, as when leaving a gas station or coffee shop after a short visit, the 7M-GE and 7M-GTE engines may  exhibit weak idling, hard starting and putting around at 500 rpm for a short period. If this happens only very occasionally it is perfectly normal  and is caused by a condition called HEAT SOAK, which happens, after shutting off the engine. After shutdown the water pump and fan are no  longer cooling the engine so the heat from inside the engine comes out into to engine bay cooking everything in its way, EFI sensors say "Wako  sure is hot in here," gasoline in the fuel rail on the intake manifold is boiled {not to mention a host of other thermodynamic conditions that occur  after shutdown}. All Engineering levels are taxed.

    To combat this inherit EFI {Electronic Fuel Injection} problem a number factory installed electronic and mechanical engine control systems are  used, but under certain conditions they fail to correct the problem completely. For the most part EFI is a wonderful system allowing great fuel  economy and silky smooth drive ability so a small bug like HEAT SOAK is still a more livable end than going back to carbs. If this rough idling  symptom is happening more often than seems normal there may be a problem with one or more of the following: Cold start injector time switch,  Bad Fuel, Throttle position sensor, Plugged or restricted fuel filter or gas cap, Idle speed solenoid air valve (ISC Valve), Fuel pressure, 2 speed  fuel pump system, Head Gasket, Air intake leaks, Engine mechanical, Fuel pressure up VSV {vacuum switching valve}.

    Other points to remember about the idle speed control valve (ISC valve) are: After shutting of the engine you should here a faint clicking  sound for a short time after the engine is killed, this is normal operation. 

    Unplug the wire at the ISC valve after the valve makes its normal clicking noise after engine is shut off, will cause the engine to run in high idle  when the engine is restarted. This is a good sign that the ISC valve is working correctly. 

    When E1 & T1 in the check connector (Diag Block) are shorted, this will cause the valve to go to a standard closed position. This is the first step  in setting the curb idle and ignition timing. 

    Failure of the ISC valve is not a common problem, what should be checked is the seat section of the valve that sits in the intake manifold. When  the ISC valve is removed, this seat will remain in the hole in the intake manifold. This seat valve will get sticky and not work smoothly due to  excess carbon and deposits in the intake manifold.

    The Bardal Super Tune kit comes with a can of gunk for the fuel tank and a can of gunk to be slowly sucked into the intake manifold while the  engine is running at high idle. This gunk stuff works great. Also included in the Bardal super tune kit is a can of gunk that is sprayed into the  intake plumbing, and throttle body. Spray this gunk into the airline going into the idle speed control valve. Presto changeo the valve will most  often work fine again. Wins also makes a good fuel injection cleaning kit that works wonders as well. The Wynns kit does not have the can of gunk  spray, but it does a great job on the injectors and intake manifold.

    When the VSV for fuel pressure up is working correctly it allows the fuel pressure regulator to receive atmospheric air pressure to its  vacuum port when the engine is hot. To test this VSV you can unplug the vacuum line from the fuel pressure regulator and start the car to see if  the vehicle starts normally. If it does the fuel pressure up VSV is the problem.

    1.1: Head gaskets

    I have worked with a few unfortunate club members who have experienced grief with their 7M-GE and 7M-GTE engines due to cylinder heads  that had lost their head bolt tension becoming so loose they actually allow the head gasket to oscillate inside the engine block between the  cylinder head and block deck surface, thus damaging the cylinder head and the block deck surfaces. Damage resulting in Toyota replacing some  entire engine blocks and heads on warranty. This is a very sad thing because the 7M-GE and 7M-GTE engines are designed from the factory to  be bulletproof but this problem has tarnished the long-standing reputation for Supra reliability. This tech note series will teach you how to  make your Supra with the 7M-GE or GTE engine as bulletproof as Toyota intended it to be.

    There are several ways to detect whether your engines head gasket is ok. The best method is to have a service shop, or a friend who owns a  block test kit tests your system for a compression leak to your cooling system. If unavailable this test kit can be purchased from a Snap On  dealer or contact the manufacturer for dealer in your area. This is a test unit and test fluid that changes color with the presence of exhaust gas  in the engine coolant, the kit cost about 50 dollars Canadian to purchase and is good for many tests. Another test that should be completed is a  coolant system pressure test, test your system for leaks with five to ten PSI pressure. If your engine passes these tests continue reading to  find out what has to be done to keep it that way.

    If your system is leaking it is too late for a simple head re-torque. Usually the factory OEM installed gasket looks like mush when the engine is  disassembled after a failure. Some of the Head bolts are loose when the engine comes apart. Coolant passages and sealing rings are distorted  and compressed out of shape. The exhaust side of this engine runs very hot due to the exhaust manifold and catalytic converter design that  locates the catalytic converter right beside the engine block. The manifold and catalytic converter add a tremendous amount of heat to this  side of the engine block.

    It is always better to know that your gasket is starting to leak than to wait until the engine burns up enough coolant to cause it to overheat. In  all cases when the gasket is changed before the engine overheats and starts consuming large amounts of coolant the repair is simple and  straightforward.

    After the head gasket has failed, a combustion leak that goes undetected leads to immediate destroying of the inhibitors in the coolant, and  will set up an acid condition in the cooling system. The acidic coolant will then conduct electricity, and a galvanizing reaction will begin among  the various kinds of metals in the cooling system. This will eat away at the radiator and other parts of the system from the inside out. When the  coolant enters the cylinders the result is a poorly running engine, cutting engine life with each revolution as the coolant breaks down the  engine's lubricants. Combustion leaks in the compression ring area also force coolant away during acceleration causing excessive heat. When  acceleration stops, the diverted coolant rushes back to the area, resulting in rapid temperature changes. This is bad enough, but the  compression leak also causes the engine to blow the coolant out of the radiator and cylinder head into the overflow reservoir bottle, depleting  the coolant, causing the engine to badly overheat. This heat further aggravates the already devastating conditions in the engine by causing the  metal alloy in the cylinder head to expand, stretching the head bolts and further compressing the bad head gasket.

    After the engine cools down the head bolt tension due to the heat expansion is relieved, leaving what is left of the original head bolt tension  from the torque up at the factory. Due to the mashed head gasket, internal surface damage, and warped cylinder head, the factory bolt  elongation is all but used up.

    Recently I purchased a pair of new head bolts from my local Toyota dealership. One bolt from the 1995 Supra 2JZ-GTE engines, as well as a  new bolt from the 7M-GTE. I then contracted a local certified engineering metallurgical company to perform tensile strength tests on the head  bolts to compare yield strengths and torque values. 

    I have lab data reports based on the ASTM A370 tensile test, giving tensile strength, yield strength, ultimate load, yield load, as well as  deformation data and maximum tightening torque values for the head bolts from the 2JZ GTE and 7M-GTE engines. Some results of the test are  given below. 

  7M head bolt is: 12mm-1.25mm thread pitch {Property Class 10.9 grade 8} yield strength=147,353 PSI... tensile strength=160,550 PSI... ultimate  load=70,198 N... % elongation=17... % reduction of area=66 2J head bolt is: 11mm-1.25mm thread pitch {Property Class 10.9 grade 8} yield  strength=148,948 PSI... tensile strength=162,581 PSI... ultimate load=68,997 N... % elongation=19... % reduction of area=66 

    The metals used in the head bolts of the 7M & 2JZ engines are identical in metallurgy +/- manufacturing S.P.C. This is a good material; it  stretches smoothly in the plastic region of the curve before it snaps.

    By calculating the unit strain for each of the different areas of bolts based on the average yield strength, the following total elongation  numbers were calculated. The 7M bolt has a total elongation of .0134" {.3399mm}, and the 2JZ bolt has a total elongation of .01093" {.2775mm}. 

    By comparing the elongation differences of the bolts, related to the corresponding different thickness of the aluminum in the engines cylinder  heads, and allowing for the total length of the bolt shank plus 50% of the length of the threads, the only apparent difference is that the 2JZ bolt  has 36 percent more thread than the 7M bolt does. The 7M & 2JZ bolts appear to be designed with the same steel to aluminum expansion stretch  theory. I believe the bolt designs are different only because of the different ratio of the bolts metal area versus the thickness of the aluminum  cylinder heads the bolt is designed to hold down. The torquing procedure for the two head bolts is also different, as is the head gasket

    Toyota service manuals say that the 7M engines head bolt torque specification is 52 to 58 ft. lbs. According to my findings the 52 to 58 ft. lbs.  specification for the 7M might be too low a torque value to keep the bolt in acceptable tension, not to mention the normal compression of the  head gasket after time. As mentioned earlier many 7M engines that experience head gasket failures have many head bolts that can be  removed from the engines failed cylinders by hand, or are very loose when removed.

    My calculations show that the 7M head bolts when torqued to the factory specifications of 52 to 58 ft. lbs. is in very low tension related to the  bolts actual yield curve. Calculations based on my test data show torque values for the 7M head bolt could be as high as 68 ft. lbs. to 72 ft. lbs.  without putting the bolt into the plastic region. On a cold engine this extra torque would allow more tension on the head bolts after the head  gasket compresses to normal operating thickness. 

    Many Supra owners that can afford it are upgrading their 7M engine to the expensive HKS stopper type metal head gasket for the 7M engine.  This gasket comes in a number of different thick nesses. My Company stocks the HKS gaskets and I ship them all over the world. The HKS gasket  will hold well to over 20 PSI of boost over 400 hp as sea level with upgraded fuel and turbochargers. The factory head bolt torque may be  satisfactory with a metal head gasket since metal head gaskets do not deform as much as the soft OEM gasket used in the 7M. I would still  recommend torquing the bolts to 72-ft. lbs. When upgrading to Metal head gaskets much must be considered with regard to machine work and  the finish of the engine block deck and cylinder head gasket surface. See the following link for full details on doing correct machine work to your engine;

http://www.supras.com/~riemer/HKS/hksgaskets.html

    I have many club members running well over 20 lbs boost at sea level with no head or engine failures using the metal head gasket. This  problem is not exclusive to the Toyota Supra! Many other automotive manufactures have this problem with their engines: Ford, GM, Chrysler &  Mitsubishi to mention a few. Good head gasket condition is a fact of life with any high output engine. GM is currently working with new head  surfacing techniques that will hopefully solve their problems with the QUAD 4 and others.

    The solution to diverting this problem has turned out to be a simple lesson from the old book of Forgotten Fundamentals 101, chapter one  "MAKE SURE THE DARN THING IS ON TIGHT". The only problem with this statement is that for some of the 7M's it is too late the gasket may  already be bad. The head bolts needed to be re-torqued after the first 20,000.00 km's or tomorrow if yours has never been done, you may be  able to save yourself a future head gasket repair job. I recommend a higher torque value than the factory, 70 foot/pounds versus 58  foot/pounds. Re-torquing the head is not a hard thing to do if you have mechanical background skills and the correct tools including the SST  {Specialty Service Tool} for the head bolts. If you are uneasy about doing it I will recommend you to a club member or service shop in your area.

    Following the factory recommended torque pattern, back of one of the head bolts one crunch or about 1/8 of a turn before re-torquing to 50  and then to 70 foot/pounds in two separate steps, following the correct pattern in your Toyota service manual, repeat this process for the  remainder of the head bolts. Note: If any of your cylinder head bolts do not make the crunch sound when you back them off the 1/8 of a turn, or  they feel as though they will turn very easily STOP! Don't turn that head bolt anywhere: it is already loose and you can thank your lucky stars  that your head gasket is not already gone south. I have seen a number of cars that were still running ok, even passing the pressure test with one  or more loose head bolts. After completing the re-torque on engines with loose head bolts it is a good idea to pressure test the radiator every  week for a number to weeks to be sure the loose bolts caused no gasket damage. Another good tip is to keep an eye on your overflow bottle  day to day. It should remain at the same level when the engine is cold before startup.

    If your engine has a damaged cylinder head and block deck surfaces it is too late for you to just install a new head gasket, but there is still  some light at the end of the tunnel, you can get back on the road again: The good news is there is ample extra metal in the  cylinder head deck surface and the block deck surface, up to 60 thousands can be milled from the surfaces without running into valve piston clearance problems with the stock gasket. You can only mill the head when the camshaft bearing saddles are within correct tolerance of 5  thousands of an inch maximum run out see section 1.01 below for more details. Please call with any questions you may have before you do any  cutting. The best thing to do when assembling the engine is to use the HKS steel head gasket. Because HKS makes 3 different thickness of  gaskets, in most cases using the HKS 1.5mm steel gasket will reduce the overall compression ratio lower than the original factory ratio. Fixing  the engine with the above method will yield a bulletproof 7M GTE, as I have mentioned earlier safe, to over 20 lbs of boost with my upgraded  fuel components. Sometimes when an engine has had a bad head gasket and the owner keeps driving the car, the corrosion from the acidic  coolant causes the head bolts to look like they have been eaten away in the area where the bolt comes out of the block. See 7MHEADGA.reg at  the FTP site. When this corrosion is present, the head bolts must be replaced. You should only use the stock Toyota or ARP bolts (Automotive  Racing Products Phone #1-805-287-7223. ARP Automotive Racing Products manufacture a high performance head bolt set for the 7M. This bolt  kit is very high quality and will work excellent in your 7M engine, don't use the ARP head stud kit, 85 Ft/lbs on the ARP bolts is adequate.

    1.2: Valve Adjustments & Misc.

    While the engine is open to re-torque the cylinder head it is a good idea to check valve lash adjustments, most often they are always within  factory tolerances: {8 thousands intake 12 thousands exhaust}. If an adjustment is required consult with me and I will forward you to an  experienced authorized shop. Adjusting the valve lash is not a hard job but requires some SST's and a selection of correct shim pads {available  from Toyota}. Replacing the valve cover gaskets at this time is a good idea; they are usually brittle and will most likely leak if not replaced. You  should also have a close look around the motor for cracked, loose or damaged air intake plumbing and vacuum lines. Also re-torque all of the  14mm nuts on the exhaust manifold to head as well as 14mm nuts at exhaust manifold to turbo.

    1.3: Cooling System

    All early model MA-70 & 71 Supras have is a small rubber plug {part number#90339 16001} installed on the engine coolant transfer pipe  {where the hoses to your heater core come from next to the top, right, rear corner of the 7M GE and GTE engine block}. Because this small plug is  located in a very hot area of the engine bay {between the exhaust manifold and firewall} it has a tendency to dry out and crack on older Supras. If  this plug comes off all the engine coolant will be expelled onto the exhaust manifold making a super big mess and steam show, as well as  damaging your engine due to overheating. This plug is very inexpensive {five bucks} and must be replaced when you have this seasons coolant  change. "Never work on coolant system when engine is hot".

    It is important to change and flush engine coolant every year; always use the best quality product you can buy. The thermostat should also be  changed if there is any instability in the temperature gauge, the gauge should always run at the same position while cruising down the road,  there should be no fluctuations in the gauge reading such as a steady climb and fall of the needle over a two-minute period. I recommend using  genuine Toyota thermostats as many of the after market brands do not work correctly for some unknown reason. It is very important to use a  thermostat. Without one the radiator will not cool the coolant down before it lets the coolant into the engine again, this will cause the engine to  over heat.

    Toyota radiator hoses seem to last forever but be sure to inspect them for cuts and cracks, also fan belts and the clutch fan should be  inspected. I am experimenting with a new product called Polypropylene Glycol coolant which is non-corrosive and safe to the engine and the  environment. This coolant offers better heat transfer capabilities than traditional Glycol.

    Your fan is used to cool your Supra on the highway as well as in slow traffic around town. Depending on engine load and conditions the fan will  engage at some times to cool the radiator. In the front of the clutch fan there is a coil loaded thermostatic bimetal coil that will engage the fan  based on air temperature passing by the fan blade. On many older Supras after many miles the seals around the temp coil will start to seep the  viscous oil from the fan clutch assay, after the loss of the oil over time the clutch fan goes on holidays and your motor gets the added benefit of  about 4 hp and no fresh air intake. One of the symptoms of this problem is a floating temperature gage. See PMTN for MA-60.

    Depending on your body code there are one or more electric fans already installed on you're supra. If you want, you can wire up a simple relay  logic box and switch that will allow you to fire the fans at will when the ignition key is in the on position, When you do this make sure you do not  confuse any other factory systems, will the fans come on whenever needed. This is a cool upgrade for turbo cars I have my AC fan setup to run  for 3 minutes after engine shut down if desired, the MA67's small AC fan pushes away a wondrous amount of heat from the engine compartment.

    Another super upgrade for MA-60 is to replace the 5M-GE clutch and fan with the 7M-GTE unit. Some trimming of the fan shroud is needed but  your supra will run as cool as a cucumber. The 7M GTE fan and clutch move a sizable amount of extra air through the radiator.

    1.4: Intercooler System {Turbo Only}

    The Intercooler used in the Supra Turbo is of the air to air type, this means it uses the air the car drives through to cool down the hot air that  was sucked in through your engines air filter before being pressurized by the turbocharger on the way to your engine. The stock Intercooler on  the MA-71 Supra Turbo has proven to be mostly trouble free, the only problems with it have been in three areas relating to maintenance:

    Because the Intercooler sits in front of the air conditioning condenser that sits in front of the radiator, the Intercooler tends to be a rock &  bug stopper. A small firm bug screen installed in front of your Intercooler is all that is needed to save it from most rocks. 2 If the Intercooler  is plugged with bugs you may want to remove it to have it professionally cleaned by a reputable radiator shop, I would recommend you ask to  wait at the shop while they do the cleaning job for you. This is a very expensive and high quality and useful part that could be used on many  other performance cars! Cleaning the Intercooler will return its efficiency to original condition of a brand new unit. If the shop has the  equipment I would also recommend that you have the Intercooler pressure tested to be sure nothing has punched a small hole into it. 3. The  other item that should be serviced relating to the Intercooler is the plumbing pipes and hoses that run through the Supras body. There are a  number of 75mm hose clamps that need to be checked for tightness and condition, with the combination of the rubber hoses aging and the many  miles of bouncing down the road, many of the piping connections will be loose allowing inlet charge air to escape to the atmosphere under  boost, and alternately allow dirt and grime to be suck in while under vacuum conditions. The 7M-GTE engines EFI computer cannot realize or  compensate for this air leakage therefore it will incorrectly calculate Air Fuel mixtures, causing drive ability and idling problems. This job is  easy to do by removing the under carriage splash guard and other plastic protectors, then following the air piping from the air filter to the  engine then out to the Intercooler and back to the engine again. Be careful not to over tighten the clamps because they will strip out or break. It  is normal to see a residual amount of engine oil in the Intercooler plumbing lines; this oil comes from the PVC system {Positive Crankcase  Ventilation}. Replace all cracked or broken parts with Toyota Genuine Parts {they have been designed to work correctly under all conditions.}

    1.5: OBD codes {Knock Sensor Code 53}

    There have been a number of cars with the same code problem, all the cars I have seen to date are early production type A TCCS wiring  harness with external HAC sensor {High Altitude Compensation}, there are 2 basic styles of 7M-GTE wiring harnesses and TCCS in MA-71  production. 

    On cars with a check engine light with a code for knock sensor coming up when shorting E1 and T1 in the diagnostic block located next to the  cars battery. This code 53 would clear fine and then come back after a trip around the block and back. All early 7M-GTE's use 2 trip logic, this  means that the check engine light will not come on until the problem has existed for two engine start stop cycles.

    The problem is an open circuit or a short to ground in one of the two wiring leads to the engines knock sensors. To fix it you have to run two  lengths of small gauge shielded coaxial cable along the TCCS engine wire through the fire wall connecting the correct knock sensor pins on the  TCCS to the knock sensors mounted in the 7M-GTE engine block under the intake manifold. I use one length of 20awg 50-OHM coaxial cable for  each knock sensor. Use the centre wire in the coaxial cable to connect the sensor and the ECU, connected the shield part of each coaxial cable  to body ground by the ECU. After you have this coaxial cable hard wired into your car between the ECU and the knock sensors the code 53 will be  gone forever.

    1.6: Oil pressure / 7M engines

    A common problem with some MA-70 cars is a faulty oil pressure-sending unit. If you have a bad sending unit your oil pressure gauge may  read very low. The sending unit is not hard to change if you are handy with your tools. But I will caution you that, you should have your service  shop test your oil pressure with a mechanical gauge. When this happens, I could be that your turbocharger, oil pump or engine bearings might be  bad. You should have this simple test done to be sure you have correct oil pressure. I have had club members loose their engines over a turbo  failure. Check it out now to be sure.

    Note the 7M-GTE does not have a lot of pressure at idle, the test spec from the bible is 3000rpm 2.5kg/cm {36psi} to 5kg/cm {71psi}. At idle  your dash gauge should be at least 0.3 {4.3psi} to over 1 kg/cm {14.2psi}

     1.7: 7M Cylinder Head Work and machining

    When the time comes to work on your 7M engines aluminum cylinder head there will be a number of decisions to make. You will have to find a  good machine shop; this will take some asking around. I would talk with the local drag racing guys. You will have to check out the shops; many of  the shops will not be experienced with your engines cylinder head. They will tell you they cannot machine it and you should not do this or that. In  some cases they are correct and in other cases they may be dead wrong. I wish this process were easier to explain it not.

    I hope that this tech note file will help explain some of the thought process that must go into the decision of: Should I cut the head surface or  leave it? Should I try to have the head straightened or leave it alone? Do I have to replace the cylinder head with a new one from Toyota or  find another used cylinder head to have check out?

    Don't pay cash for a used head until it checks out. Most reputable salvage yards and parts dealers will allow you to have the head examined by  the shop of your choice. If they will not let you do this take your business somewhere else. It would be an easy big money business to be selling  scrap aluminum for three hundred dollars a bar. Valve guides in the 7M engines seldom need to be replaced. If the shop you are dealing with says  you need new ones you should question this!

    To determine if your cylinder head is suitable to machine you must have a good understanding of the following test procedures, and the  thought process relating to warpage. If you do not understand the methods of the testing, that's ok, leave this to your machine shop. However it  is important that you understand the concept of what I am trying to explain. Read on, as I will try to explain some of this below. I would  recommend that you print this file so you can circle areas you want to ask questions about.

    Remember that the head is not just warped at the deck where you measure it, the entire head is warped along with the deck. This means that  the ports, valve cover gasket seal area as well as the cam saddles {what the cams spin in} are all warped x.x thousands of an inch. Following this  idea if you have lets say 10 thou warpage in the deck surface when you measure it, the cam saddles should also have this 10 thou warpage if the  head has not been machined before. If you bolt the warped head back on the engine and torque it down this will pull the head straight again  providing your block deck surface is flat. Think of it as a banana on a table, if you pull the banana flat to the table it will look straight. When  you let the banana go it will look curved again.

    Now lets consider what happens if you cut the 10 thou of the bottom of the head or the banana! The deck surface of the head is now perfectly  flat, but the cam saddles, and basically the entire head is still warped 10 thou. The banana is still curved but it has one side that is flat. This is ok  as long as the cams still turn smoothly in the head when you have it bolted down to the engine.

    Inspect the cylinder head for warpage in the deck and cam saddles. If the deck is warped less or more than the cam saddles you have a head  that has already been machined at least once. If the head has not been machined before you will be able to tell because the warpage will be the  same amount and in the same direction on the cylinder head deck surface and the cam saddles. It was all straight at some point in time. Because  an in line 6 is a long engine a small amount of warpage is normal.

    Carefully inspect the deck surface of the cylinder head for any compression ring groves left by the gasket that are deeper than 5 thou  maximum. The engine block must also be inspected very closely for grooves in the block surface. If there are marks in the deck surface of the  block they will almost always be on the exhaust side of the deck surface. If they are deeper than 5 thou you should have the deck of the block  machined as well to get a better than new repair. Remember to have your timing cover machined along with the block, it also must be  machined down to the height of the deck surface. The shop will bolt it to the block and cut them together.

    If your cylinder head is free of groove marks in the deck from the gasket that are deeper than about 5 thou maximum and your head is not  warped more than 8 to 10 thou, you will have no problem cleaning the whole thing up and installing a new stock Toyota gasket.

    If your head has grooves deeper than 5 thou from the compression ring in the deck surface, you must machine the surface of the head in order  to reuse it. The question is can you machine this head safely. 

    Checking cam bearings saddles. The factory says that maximum warpage should be within four thousands /inch. Bearing clearance should be  two thousands minimum, five thousands maximum.

    For the most part these specs work out, but I have seen some heads, where the bearing saddles were warped as much as 20 thousands across  the length of the head. This head only had 12 thou warpage on the deck, this told us the head was machined once for sure. The cams still turned  smoothly with the valves and followers removed and the head sitting on the workbench. The warpage in the cam saddles stayed at 20 thou after  the head was bolted down on the engine, this was because we machined the head flat, removing the 12 thou warpage from the deck surface of the  head. This engines block was only warped 1/2 thou. I believe when the cams turn smoothly there should be no problem using the head. I have not  had any problems with engines we have used heads like this on, but it is a calculated risk. If you can afford to buy a new head it may be worth  your time and money in the long run. I will keep the club posted on any new information in this area.

    If you measure the 7M's block deck and it is flat you do not have to try the bolt down test because it will not tweak the head any different than  if the head sitting on the workbench.

    If your engines block deck surface is warped you should check the turning smoothness of the cams when the head is bolted down to the block,  use your old head gasket for testing purposes and torque the head to 52 foot-pounds. Depending on how much and the direction of the warpage  in the deck of the block and the cylinder head, if it was not machined flat, this joining of surfaces will add or subtract from the now built in cam  saddle warpage.

    If you machined the surface of the head before installing it on the motor the bolt down test should not change the feel of how the cams turn  compared to when you turned them on the bench. If your engine block deck surface is not warped. Remember that this test must be done with  the valves and bucket followers removed. If you attempt to do it with the valve gear in place you will only feel the resistance of the cam lobes  compressing the valve springs. What you are trying to do is feel how the cam turns by itself when installed in the head.

    You should use good assembly oil or lubriplate grease on the bearings. Also note that the bearing journals on the 7M cams are coated with a  soft bearing material that is easy to scratch and mark up. Most 7M's will have these scratch marks when you pull the engine apart. What you may  see are scratch marks on the journal that look like a badly galled up bearing journal. This may look bad but is normal and will not hurt anything.  Do not attempt to clean the surface of the cam journal. Just inspect it for bad cuts or grooves in the journal that is into the cam material not  just marks in the soft journal coating material.

    Section 2 ~Drive Train   2.0: Transmission

    For more than a decade the only transmission complaints or problems reported by owners are related to how can my Toyota Supra  transmission shift faster and slicker than it does already. Supras have always had very smooth, strong & slick gearboxes, the 1982 to 1991  {W58} in the MA-67 and MA-70 non-turbo as well as the R154 in the MA-71 turbo have all proven bulletproof to the end! Therefore the only  suggestion I can give you is toward advice on lubrication. Winter cold climates use Dextron 11 if bearing noise or hard shifting is experienced  when cold, do not be alarmed by a small amount of input shaft bearing noise, this is normal with some Toyota transmissions. Also a ticking or  slight squeaking sound can normally come from the clutch release bearing. Summertime use Red Line or Amsoil synthetic gear oil. These oils  work wonders in Toyota boxes, reducing friction and making the gears slide easily. I run a W58 transmission in my 82 Supra with a 7M-GTE and  have experienced fantastic reliability at over 325 hp.

    The automatic Transmission used in the MA-70 and 71 Supras is called the A 340 E. It has also proven to be bulletproof and shares duty in  other Toyotas such as the current Lexus LS400, SC400, GS300, Toyota 4Runners, Pickups and the Supra JZA-80 TT. Be sure to change the oil on a regular basis. You  change it by draining the pan but you can only change 2 liters of the oil at a time, so change it when you have your engine oil changed, this way  you will eventually replenish all the old oil with new. The best way to change the oil is to have a good oil change shop like one of the penszoil ones use their oil transfusion machines

    2.1: Drive Shafts

    Supra drive train components have always been very robust, however some owners and service shops always seem to be able to find a way to  damage the odd one. Relating to Drive Shafts be very careful when you are told by a service shop that you need to have your Supras U Joints  replaced. In 12 years with this club I have never seen a drive shaft that was so worn out that the joints were loose. If you have a vibration or a  noise please do not assume that your drive shaft is worn out. If you let just anybody try to install U Joints in any Supra 1982 to 1995 drive shaft  you will most definatly get your car back with the original noise you were concerned with fixing plus a few new ones to boot. Please call me  with any questions relating to drive shafts. Note: Supra drive shafts almost never fail on their own they need help from: car accidents, rust,  inexperienced service shops.  Also be sure that the drive shaft is in correct phase, or that the joing flange joint is not out ninty degrees when its bolted up.

    2.2: Differential Carriers

    Another condition that may trouble your Supras differential is lack of regular oil changes; this will lead to differential failure or premature  wear out. The MA-70 differential holds a very small amount of oil so it needs to be changed regularly. Cold climates are very hard on the  differential. I recommend using a good quality synthetic in cold climates. I do not recommend standard 80/90 wt oils in any Toyota differentials  used in cold climates. Using 75/90-wt LSD differential carrier oil from Ford motor company makes Supra differentials run quieter and smoother  than any other oils tested.

    Some LSD differentials in MA-70 and MA-71 cars have excessive LSD {limited slip differential} cage pressure causing premature clutch pack  failures after some cars have become stuck in mud or snow, I have opened up badly abused differentials where the LSD oil is completely burnt  and Dried up from the heat of one wheel smoking while the other is locked. If you notice some chattery noise from the rear of the car when turning  corners donít panic: you have a supra with a very tight LSD differential carrier. On a Supra with tight LSD you can avoid the above clutch pack  failure by using the previously mentioned LSD differential carrier oil from Ford motor company. This oil has increased protection for the  clutch pack and has proven to be the best differential oil for all Supras from 1982 to 1992. Don't ask me why, all I can say is this oil works like  magic. Note: A number of club members are using synthetic oils from Amsoil and Esso in their differentials with good results, one word of  caution should be noted." Synthetic oils may make a some differentials that are already noisy, noisier."

    2.3: Front & Rear Wheel Bearings

    Unlike the front wheels hub and spindle setup on the MA-60 series cars the MA-70 front wheels are spun on a pressed in bearing. Because of  this pressed in bearing arrangement it is impossible to just quickly disassemble the bearings for service and greasing. Because of the  un-serviceability of this area, it never gets serviced, and as it turns out the wheel bearings have never been any problems what so ever. The  only way you can hurt them is with curbs and accidents.

    Section 3 ~Suspension 3.0: Front lower A Arms

    On some 87 to 89 MA-70 and MA-71 cars there can be a problem with lower control arm bushings moving around allowing control arms to make  a thumping sound when driving on rough road surfaces such as packed and rutted snow and ice on roadway, this condition is more pronounced in  cold conditions. Note: worn out shocks or ball joints can also make similar sounds to be sure lift car with front wheels up in the air to look for  excessive fore and aft movement in lower control arm bushings; this movement, when excessive, allows the arm to bump into the front  suspension subframe of the car causing the noise. Because the control arm bushings come with the control arm you cannot just replace the  bushings. Some club members have custom fitted plastic bushing into to old arms to solve the problem. I don't think this is the best solution,  "TOO NOISY ALL THE TIME". 

  I have talked with some after market manufacturers regarding a rebuilt arm or a rubber bushing kit. Call for more details. This problem is really  not a serious mechanical defect that makes the car unstable or dangerous to drive, but is a definite annoyance if you have a Supra with it. The  arms are not worn out but are moving just enough to cause a small amount of contact between the front suspension subframe and the control  arm.

    Section 4 ~brakes 4.0: Brakes

    On cars driven in salty conditions it is normal to see the rotors corroding very badly causing the cooling fins to become ineffective. After  market rotors are cheaper but will wear down if you use the stock pads. If you use after market rotors use after market pads as well. Many  years ago a smart guy told me "never handle new brake pads or rotor surfaces with your bare hands because the oil on your skin will cause  glazing of the pad material. I have had many people crying with tears over this but to this day I have still not proven this statement wrong or  right. I still use it today because it makes a certain amount logical sense, why do I have to touch the surface of the parts to install them? I donít.

    Another important tip for all MA-70 cars is to be sure not to over tighten the wheel lugs. The factory torque spec is 55 foot/pounds, always  torque to this value. I have seen Supras where the wheels lugs were torqued to very high values 140 foot/pounds, this can cause rotor distortion  resulting in brake pedal pulsation. I always torque the wheel nuts with a torque wrench.

    Always check all your brake lines, it is very rare to find cracked lines but cars driven in cold climates sometimes have fine cracks. Another  good preventive Maintenance tip is to flush your brake and clutch master cylinders reservoir out with new fluid every two years, always use  good quality fluid and be careful not to spill any brake fluid on your Supras paint because it will damage the paint on your car.
 
 

    Regards

    Reg Riemer

    SONiC 
 


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