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S.O.N.I.C. Presents:
Preventative Maintenance Tech Notes (PMTN)
1987 to 1992 Supra MA-70 & 71 Series Non Turbo & Turbo v3.5
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 "Wahoo 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 inthe intake manifold. When the ISC valve is removed, this
seat will remain inthe 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 air line going into the idle speed control
valve. Presto changeo the valve will most often work fine again. Wynns 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 test 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
may 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 engine, as well as a new
bolt from the 7M-GTE. I then contracted a local certified engineering
metallurgical company to preform 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.
Head gaskets 1.1: continued
*7M head bolt is: 12mm-1.25mm thread pitch {Property Class 10.9 grade 8}
yield strength=3D147,353 psi... tensile strength=3D160,550 psi... ultimate
load=3D70,198 N... % elongation=3D17... % reduction of area=3D66
*2J head bolt is: 11mm-1.25mm thread pitch {Property Class 10.9 grade 8}
yield strength=3D148,948 psi... tensile strength=3D162,581 psi... ultimate
load=3D68,997 N... % elongation=3D19... % reduction of area=3D66
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.s to 82 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 thickness. HKS USA is located in Torrance
CA. they are an importer of the HKS products from Japan. The HKS gasket
will hold well to over 20 psi of boost over 400 hp as sea level. 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.
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. The head gasket 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 kms 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! Dont 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, a couple of ways you can get back on the road again:
1{Cheapest} Patch up the groove marks in the block with a special compound
and resurface the cylinder head if possible {call me for details regarding this}.
2{Best} 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 cam shaft 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 HKS 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.
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 with out 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 hpand 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 your 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 MA-60's small AC fan pushes away a wonderous
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 sizeable
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:
1* Because the Intercooler sits in front of the air conditioning condenser
which sits in front of the engine 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 Supra's 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 drivability 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 a open circuit to one of the engines knock sensors. To fix
it you have to run a length 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. By running a hard wired system to 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 may be bad. You should have this simple test done to
be sure you have correct oil pressure. I have had club members loose there
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 was easer 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 a 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 work bench. 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 work bench.
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 a 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 are 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 and
Pickups. 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.
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.
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 a 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 don't 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
=46ord 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. Aftermarket
rotors are cheaper but will wear down if you use the stock pads. If you use
aftermarket rotors use aftermarket 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 to
install the parts? I dont.
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 peddle 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.
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