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RE: First MGB Clutch

To: mgs@autox.team.net
Subject: RE: First MGB Clutch
From: "Dodd, Kelvin" <doddk@mossmotors.com>
Date: Wed, 2 Nov 2005 17:15:38 -0800
Steve:

Sorry, but I don't know of any good web resources for this information
other than to search the archives. 

It is a pretty straight forward job when approached step by step.

Note:  Probably everything on your car is pretty well worn.  I'm going
to suggest some areas that are typical failure points that you will be
working around.  You don't have to address them now, but it's a good
idea to be aware of them.  These are the areas that I prefer to know the
history of with my own vehicles, so I've got a clue how long they are
going to last.  Or I know that when I have to do a job, the existing
bits will come apart correctly.  

Personally I hate having to wrestle an engine back onto the transmission
shaft in the engine bay.  My preference is to remove the engine and
trans as a unit, that way it is easier to clean everything plus the rear
engine mounts have usually turned into gummy globs (technical term).

Disconnect the battery first!  You will be swinging wrenches close to
the fuse box when disconnecting the oil lines, and you won't remember to
disconnect it at that time.  BTDDT

On your 71 you have a prop rod, so you won't have to disconnect the
bonnet support.  I tie a piece of line around the bonnet catch and pass
it to the back of the car where I secure it to the boot handle.  This
allows you to pull the bonnet till it is almost vertical and out of the
way.  You can do the same thing with an adjustable prop rod, without the
fear of it landing on your head.  

There are lots of different preferences as far as stripping the engine
bits.  I prefer to take the carbs off, so they don't get damaged.  I
also prefer to leave the exhaust manifold connected to the down pipes as
I hate to have to replace the down pipe gaskets.  It is easier to pull
and install the motor with the exhaust manifold completely removed, so
for your first time that is probably the way to go.  You are also
getting to know the car, so if the manifold to down pipe studs are
frozen, now is as good a time as any to fix them.

Once the manifolds are off, drain the coolant.  Your car probably has a
drain on the bottom of the radiator.  You can very carefully turn the
arm of the drain with a pair of vice grips, if the arm is frozen stop!
Pull the lower hose to drain the radiator, you can free the drain valve
later after the radiator is out.  If the drain valve worked ok, make
sure you close the valve back up after all the water is out.  BTDDT

Undo the bolt holding the radiator diaphragm to the inner wings.  You
can loosen and swing away the two support struts.  Let the diaphragm
rest on the wings.

Disconnect the oil cooler hoses from the engine block and oil filter
adapter.  In the past I have never had the right tool, so ended up using
a 15" crescent wrench for this job.  The lines will leak all over the
place and continue to dribble for weeks, so be prepared.  I usually
stuff a clean piece of rag into each hose, followed by a diaper like
cover wired in place.

Unscrew the 4 x 1/4" bolts holding the oil cooler to the front apron.
Now you can lift out the diaphragm/radiator assembly with the oil cooler
lines and cooler.  Take this lot off and give it a good clean.  Look out
for leaks in the cooler as evidenced by the back side being full of goo.

Disconnect all the wiring, this is all pretty obvious, but don't forget
the wires that go to the transmission switches.  Be very careful with
the wiring to the temp sender and alternator as these tend to be very
brittle.  There is a ground strap across one of the engine mounts.  Make
sure this gets cleaned and reattached when you put the motor back in.
Simple enough, this has to go from one side of the mount to the other,
allowing a connection across the rubber.  Simple, but lots of people get
it wrong.  Your car should have L shaped restraint brackets on top of
the engine mounts.  Pay attention to how they are installed and
understand how they will prevent the engine from sliding forward into
the radiator.  Disconnect the main battery cable and other bits from the
starter.  All the big brown wires go to the same terminal as the battery
cable.  The white/red wire is starter switched and goes to the smaller
terminal to the side.  Make sure these connections are degreased and in
excellent condition when you reassemble.  Don't lose the starter motor
main terminal nut.  It is brass and I think BA thread.  

Inside the car, undo the gearshift boot surround and pull it up to the
shift knob.  Looking in the hole you will see 3 x 1/4" bolt heads.
Carefully remove these.  They are special stepped bolts with multi coil
lock washers (sorry, forgot the technical term)  Thackeray?  With the
hold down plate removed the gear shifter pulls straight up and out.  It
will probably come out with the plastic cup still attached to the ball
end, it's a good idea to get a new one of these if it looks iffy.  To
the side of the shifter socket should be a small brass button with
spring.  This is the anti rattle plunger.  

By the way.  All of these things I'm describing tend to be missing on a
lot of cars.  If they are missing, I would strongly recommend putting
them back.

Jack up the car and place jack stands under the rear axle and under the
horizontal section of the front frame rails by the engine. 

Time to crawl under and disconnect the drive shaft.  It's always a good
idea to mark the flanges before removal, although I tend not to.  The
bolts on the trans side are captive, so pretty easy to undo.  It is a
good idea, since you are down there and new to the car, to drop the
drive shaft out completely so you can be sure the u joints are in
excellent shape.  With the top down, it is difficult to hear a bad joint
and its not a happy time when they go.

Undo the two bolts holding the clutch slave to the side of the bell
housing.  Let the pushrod pull out of the slave boot and tie the
assembly back out of the way.  

Important.  Iffy hydraulics will fail when you install a nice new
clutch.  That's just the way percentages work.  At the very least since
you are down there, I would suggest dismantling and inspecting the
slave.  If the bore is ok, then new rubbers are cheap.  Personally if
this was my car and I did not have an idea on the history I would be
replacing the master, slave and hose.  You probably are not going into
this with the idea of doing a full ground up restoration, so if the
hydraulics have not been acting up and the hose does not have age
cracks, just leave them alone.     

Put a trolley jack under the drain plug of the trans. This is a good
place to use one of those small roll around units that cost $20 from the
local parts store.  Undo the 4 bolts holding the cross member to the
chassis.  Carefully lower the rear of the trans down a bit to make it
easier to remove the speedo cable.  Then remove the bracket by taking
out the bolts attaching the trans mounts to the trans case.  Note, these
are coarse thread bolts.  Before reinstalling the transmission, make a
note to carefully check the condition of the case threads.  These are
often stripped and you don't want to find that out after stuffing the
power train back into the shell.  

If you havn't done it already, now is the time to disconnect the head
pipe from the manifold.  This is not essential, but makes the job a lot
easier.  The manifold studs should be replaced with new, and new brass
nuts secured along with the new gaskets.  A lot of times the studs are
totally frozen, so be prepared to either live with the originals, or
spend lots of time fixing the manifold.  

If your hoist has limited height, now is the time to lower the front of
the car back onto it's wheels.  Remember not to bind up the trolley jack
that should stay under the car, that's why you got a spare one for $20.
This is when all the antifreeze still in the block comes pouring out.
After you finish cleaning up, now is a good time for a breather, because
you are almost there.

The trolley jack under the trans should be in line with the engine.
Just lift the trans high enough for the rear flange to clear the fixed
cross member as you are lifting on the engine.  This is one of those
tips you were asking about.  

Some kind of tilt lifter is absolutely the way to go.  I use the Oberg
and have been very happy with it over the last 15 years.  You can get by
without if you have friends, but if you are on your own I would
absolutely recommend something to help carefully tilt the assembly.  

I usually hook around the water pump arm and one of the rear manifold
studs.  Your mileage may vary.  I like picking on this diagonal, but
usually the alternator is off.  There are special brackets that mount on
top of the rocker cover studs, but I'm still a bit squeamish about using
those.  Make sure to protect the rocker cover with padding where the
cable or chain is going to press.  Set the lift so that the engine comes
almost vertically upward.  Lift the motor off the mounts until the bell
housing is about to hit the top of the tunnel and the front pulley
clears the rack.  At this point you should be able to slide the motor
forward carefully about a couple of inches over the rack.  Check
underneath, and you should see that the rear flange has cleared the rear
crossmember.  You can now let the trolley jack down, but you should be
able to leave it in place.  The engine now comes straight up with the
transmission tail free to follow  Carefully pull the assembly forward
taking care not to ram the bonnet shut panel.  Now is the time that the
tilter pays for itself, as the engine now is lifted and tilted at the
same time as it is pulled up and over the shut panel.

Things to check.

Always replace the rear main seal.  Make sure the seal is greased before
installation, or it can glue itself to the crank.  

Check the rear main area for wear.  Most cranks now have a lot of wear
and a seal saver should be installed.  

Installing a new front gearbox seal is always a good idea.  

Usually the pilot bush in the back of the crank is in good shape and
does not have to be changed.  Check it carefully and put a smear of
grease on it.

Check the clutch fork bushings and bolt.  Plan on replacing the rubber
dust boot, as it is usually torn.  

When installing the throw out bearing.  Check to make sure that the
pivot points do not bind.  There have been some TO bearings coming
through with too tight of a clearance for some TO forks.  With the
retaining rings installed the bearing should still be easy to move.  If
not, the bearing pivot shafts may need to be dressed for clearance.

Get some new 5/16" nylock nuts for the driveshaft.  

If the engine to transmission bolts look iffy or some are missing
(pretty typical) I do recommend the bolt kits supplied by your favorite
mail order houses.  These bolts are very unique with 1/16" increments
and not to be found at the hardware store.  The kits are cheap and it is
nice to have the right stuff when you reassemble.  


As the Factory workshop so merrily states.  Reassembly is the reverse of
assembly.  Personally I have never understood that, because it would be
"ylbmessa"  which my spell check program does not identify as a word
either.

I like going in with new hardware for the radiator diaphragm, oil
cooler, trans mounts (remember to make sure the coarse threads are in
good shape, any question heli coil them) 

Use the trolley jack trick to put the trans back in, and install the
trans mounts loosely to the cross member.  A combination of pry bar,
swearing and 1/4" drives are the best way to get the mount bolts into
place with the trans hanging down supported by the jack.  Now you know
why I made so many comments about the condition of the threads.  Just be
thankful you don't have an overdrive.  

Hopefully others will fill in with their thoughts and preferences, but I
hope that this gives you some ideas.  I have also found that loud Reggae
music makes the job go smoother and faster.   


Kelvin. 




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