XPAG Oil leaks - and cures
by Dave Dubois
This page attempts to pool together all
the current documents published on XPAG oil leaks. It is not exhaustive by
any means, and all opinions offered are those of the authors of the articlesand do not
necessarily reflect those of the MG Car Club Y Type Register. Please also
see our Disclaimer page. All prices quoted as of the time the
original articles were first published: they may now be different.
Although written primarily for the T Register (Dave DuBois is an active member
of the North American Northwest MG T Register), the articles are just as
applicable to any XPAG or XPEG engine.
Causes of Oil
Leaks in XPAG-XPEG engine
by Dave DuBois
I have attached a number of
articles regarding the rear main seal. There is some information on the Moss
seal and on the Bradley seal, which are two different attempts to install modern
lip seals to the rear main bearing. Both of these modifications require a
certain amount of machine work be done to the engine and there is no guarantee
that either will work properly. Both seem to work sometimes but not always.
I’m not sure that either even hits the .500 mark. There are also articles by
Chris Nowlan, John Seim and Skip Barns with three different looks at controlling
leaks. The pictures that I have attached and the description and picture in
Chris Nowlan’s article will give you a good idea of how the rear main seal is
constructed and why it is problematic. My approach on our TD (which never did
leak excessively) was a combination of Chris Nowlan’s and Skip Burns’ approach.
When I threw a rod in our engine, I had to get the block welded and also line
bored. Line boring the block caused the scroll portion of the crankshaft to rub
on the seal surface of the rear main bearing cap, so I worked the seal surface
down with a scraper, then fitted the upper seal cap and did the same thing with
it. This left the seal surfaces with less than 0.001 clearance from the scroll
surface of the crankshaft. I also paid meticulous attention to fitting the
gaskets when installing the sump as Skip Burns suggests. When we first got the
TD back in 1974, all of the technical experts really emphasized the importance
of getting the gaskets properly sealed around the rear main bearing as the
secret to minimizing oil leaks. Nobody pays any attention to that since the
Moss seal modification came out. It is my guess that a majority of the oil
leaks after installing the Moss or Bradley seals are attributable to lack of
attention to those gasket ends that we used to pay so much attention to.
You will see from Chris Nowlan’s
article that the rear main seal is not true seal as with modern lip seals. It
is, rather an oil slinger that is cast into the crankshaft and rides in a grove
in the rear main bearing cap that leads down into a catch trough and a drain
tube that extends down into the oil in the sump. There is a spiral grove just
behind the slinger that acts like an Archimedes screw to carry any oil that gets
past the slinger back to the drain grove. In theory the only oil that will
escape is what little bit is left on the groves when the engine stops. On our
car, and on a majority of cars, this works quite well, but it sometimes fail and
when it does, it is a real puzzle to cure. Some of the things that can cause it
to fail is excessive clearance in the rear main bearing, causing a flood of oil
that overpowers the slinger and threads. Excessive, or uneven clearance of the
seal surface around the spiral grove will also cause excessive leakage, as will
excessive crankcase pressure. Excessive crankcase pressure can be caused by the
tappet cover gasket collapsing against the inside of the cover, blocking the
breather pipe or by worn compression rings or worn cylinder walls
Some people have removed or cut
off the pipe that extends from the oil trough in the rear main bearing cap in an
attempt to cure the leak at the rear. The rational for this is that the early B
series engines used in the MGAs and early MGBs have the same rear main seal
arrangement sans the pipe that extends down into the oil in the sump. Others
have drilled additional drain holes into the trough to provide more drain
capability. I disagree with the assertion that this pipe will siphon the oil
out of the sump when the engine is shut off, as that is not how a siphon works,
as the output end of a siphon has to be below the level of the fluid it is
siphoning. While I can understand how a possible air lock can develop in the
pipe extending down into the oil, my thoughts is that if the drain is being
overpowered by the volume of oil, then the rear main bearing clearance is
probably excessive. Regardless of the physics of this arrangement, it probably
doesn’t hurt anything to cut the pipe shorter.
At this point, let me go over
some of the many places that the XPAG/XPEG engines can and do leak. Starting at
the top, the rocker cover is a notorious leaker. This can usually be eliminated
by gluing the gasket to the head with a hardening gasket sealer such as Permatex
97B and insuring that the sealing surface of the rocker cover is flat and true.
I have trued the cover on our TD with sand paper on my table saw table. Next is
the tappet cover gasket. Some people use two gaskets here to try to stop
leaks. My experience is that often the head gasket extensions that go to the
left side of the engine extend a bit past the edge of the head and block and cut
into the gasket. I now check that area and file off the protruding gasket flush
with the side of the engine. Again, I glue it all together with Permatex 97B.
Another place for an oil leak is from the head gasket itself. This is more
likely due to an imperfect finish on the head or block surfaces rather than the
gasket itself. There is also a pipe that bring oil up from the gallery in the
block to the head. This pipe is attached at both ends with banjo fittings that
have a copper crush washer on both sides of the fittings. If the washers are
reused, they can start leaking. Going forward, the oil pump can be a source of
leakage as can the front crankshaft seal (more on this seal later). A
distributor with worn bushings can fill up with oil and dribble down the side of
the engine for another leak. The one thing common to all of these leaks is that
they all run down the side of the engine and get blown along the sump to the
back and when the car is stopped, the oil drips off of the flywheel housing,
which also contains the drain hole to shed any oil leaked from the rear main
seal, making it look like the rear main seal is leaking. This reminds me of
another potential source of an oil leak, and one that will definitely cause oil
to come out of the drain hole. There is a welch plug at the rear end of the
camshaft and if it leaks, the oil goes down the back of the engine and out the
Before doing anything in the way
of leak suppression, I would suggest either have the engine steam cleaned or get
several cans of Gunk engine cleaner and completely clean the exterior of the
engine. After doing that get some leak detect dye to put in the oil and a black
light. Go out and run the car for a good long run, then take it back into the
garage and start using the black light to find any oil leaks. With the limited
access in the engine compartment of the TF you are probably going to need a good
inspection mirror to do this and it may take several runs to find everything. I
don’t know how difficult it is to remove the side panels from the engine
compartment of the TF, but that is also an option while you are hunting down
The leak indication on the front
of the timing cover could be from a leaky rocker cover along the front edge, but
most likely it is the front seal or a crack in the crankshaft pulley. The front
seal is the old rope seal (graphite impregnated rope) and it rides on an
extension from the back of the crankshaft pulley. You can check the pulley
extension by removing the pulley (you may have to lift the front of the engine
to clear the front cross member) and inspecting the extension along the line of
the keyway, which is where they always crack. I don’t think that the crack
leaks so much oil as it shaves the seal away and allows the oil to go past it.
I have including a list of modern lip seals that can be used to replace the rope
seal at the front, but it requires removal of the timing chain cove at a minimum
and preferably removal of the sump. Even then, it is a bit fiddly to get this
seal installed properly because you are trying to fit it into a grove meant for
the rope seal and requires some judicious use of RTV type of sealant (the only
place other than the ends of the sump gasket where RTV sealant is appropriate in
Regarding tolerating oil leaks,
one thing that helps is to get one of the large drip pans and line the inside
with one of the drip carpets. The drip carpet is very dark in color so you
can’t see any of the drips that hit it (kind of like a little kid wetting is
pants while wearing dark pants). With this approach, you just have to be sure
that you never park the car on a light concrete surface at home. You can also
stop thinking of them as leaks, bur rather as an automatic rust proofing system
for the underside of the car. When our car wore out the cylinders, I was
getting so much blow by that most of the oil was being blown out of the breather
pipe that it completely coated the underside of the car and frame. Parking the
car in the garage after driving it very far, resulted in an oily outline of the
frame on the concrete floor – That’s excessive!
I hope that all of this helps
somewhat. If you have any other questions or if something in the above write up
is not clear, be sure to drop me an
How to Stop (Almost All) Oil Leaks in Your T-Car The Cheap and Easy Way
by Skip Burns
After thirty years of fiddling with XPAG engines, I’ve long held the notion that
the majority of oil leaks are caused by improper installation of the cork seal
on the rear bearing cap. The result has been more articles about how to fix oil
leaks in T-Series cars than on any other subject. Nearly all have recommended
installing “other car” seals, not to mention the well-known Moss crank seal. In
many cases, this means yanking the engine out of the car, extensive machine work
and money. Lots of it.
I’ve seen some
real leakers in my time, including my own car (TB). Some owners have gone so
far as to install little reservoirs under the sump in an effort to stop oil from
dribbling onto the garage floor. I know one guy who even tried to figure out a
way to get this oil back into the engine...automatically. He failed, of course.
We know that
with the initial production run of the TC, Abingdon was picking bits and pieces
out of the dustbin as the cars came down the line. Money was tight, as were top
grade materials. Nevertheless, one still reads bulletin board messages from
owners trying in vain to obtain “original” parts—like nuts and bolts for the
frame—and “original” paint colours, when few realize
that for a couple of extra pounds, Abingdon would paint polka dots on your car.
Still, I got to thinking—would Abingdon knowingly produce a car that dropped oil
by the quart? Hark, is that a tumultuous, resounding “YES!” I hear in the
background. I don’t think so.
What we have
is an older car fitted with anachronistic seals. The asbestos rope seal on the
crank pulley is a prime example of steam engine technology. Today, there is a
replacement...the lip seal. The cork seal at the rear is another anachronism,
but with care, it will work pretty well. Honest! The secret lies in prepping
the seals correctly before installation and then putting everything back
together precisely in the proper sequence, plus purchasing a few inexpensive
items from your local auto store. Will it still leak? Maybe.…maybe not. It
depends on how careful you are and if you have the patience to do it right the
first time. Doing it right requires thoughtfulness—and precise timing. If you
do this right, at least your car won’t be dropping large quantities of oil on
your pristine garage floor.
ordering up some inexpensive parts. Using the Moss catalogue
as a reference, order two oil pan gaskets (part no. 291-000). Why two? You’re
probably going to botch the first one; the standby will be your backup. At the
same time, order the one-piece lip seal (part no. 120-750) that’s going to
replace the rope seal. You’ll also need to order a timing chain cover seal (part
no. 291-600), because you’re going to be pulling the cover in order to properly
install the lip seal. TB owners will need to buy some gasket material to
hand-make a gasket, because no one makes TB timing chain cover gaskets any
more. Next, go down to your local auto supply house and purchase one tube of
silicone sealant (Permatex Blue RTV with the code 6B on the bottom) and a small
can of Permatex High Tack Spray-a-Gasket Sealant (comes is a blue can and may
have the name Loctite on it). Why High Tack Spray? Because using silicone
sealer with abandon in the wrong places can ruin your day. If you apply it to
the sump gasket and use too much, it may squeeze out and drop into the oil pan
where it can find its way into the oil galleries. Ouch! Moreover, the next time
you try to remove the sump, you may need a jackhammer to get it off. A final
word, you’re going to be removing a lot of bolts. Inspect each carefully for
stretching or corrosion before reinstalling and replace as needed.
As the saying
goes, “tidy ship, tidy mind.” Clear a bench or table where you can temporarily
store bits and pieces removed from the engine. Timing is going to play a role
and you don’t want to lose time rummaging through a pile of stuff looking for a
part you took off two days ago.
clearing the decks. Remove the radiator shell and radiator. Check the hoses and
while you’re at it and consider replacing them. Pull the fan, the timing chain
cover and drop the sump. Loosen the bolt holding the crank pulley and remove
it. This might be a good time to clean up and put a dab of paint on the TDC
mark—maybe even adding the 5 and 10 degree advance marks mentioned in Part I of
“How to do a Complete Engine Tune-up”. Remove the old cork seal attached to the
bearing cap. Clean (scrape) all sealing surfaces—sump, bearing cap, block, and
timing chain cover— scrupulously.
the sump on a bench and lay the raw gaskets in place. It helps to drop some
bolts in to keep them from sliding around. Formerly, the front end of the
gasket extended between the ends of the rope seal and was crushed by it, making
a tight seal. Okay, maybe not that tight! With the new lip seal in place, you
can easily see that the end of the gasket is going to interfere. Using a ball
peen hammer and holding the gasket firmly in place with the holes lined up,
carefully tap, tap, and tap the gasket where the lip seal slot is. This will
indent the underside and show you where to remove a tiny portion of the gasket.
If you really want to get a good seal, take care when cutting the gasket.
You’ll want those two little tab ends of the gasket to remain so they will cover
both sides of the lip seal. I used a sharp pair of scissors and was lucky
enough to remove just the right amount of gasket material. So can you, provided
your patient and work slowly.
timing chain cover and clean out the slot where the lip seal is going to be
inserted. When you certain it’s clean, apply a small amount of silicone
sealer—not too much because you don’t want any spilling out the sides of the
slot. Insert the seal and press fit it into the slot. Make sure the flat side
of the seal is facing forward and the slotted side with the spring in it is
facing toward the engine. It should be a firm fit. Wipe off any excess silicone
and quit for the day. Allow 24 hours for the silicone to cure and glue the seal
to the cover.
Next day is
Hallelujah Day. Inspect the lip seal and make sure it’s firmly adhered to the
slot. Don’t pull on it or try to rotate it, you may dislodge it causing you to
start over. Apply a dollop of grease to the inner surface of the seal. This
will prevent it being burnished when the engine is first started and before oil
pressure is attained. Assuming you’re satisfied, lay out several layers of
newspaper on a flat surface and spray the timing chain gasket with the high tack
sealer...both sides. Soak it. Insert the bolts into the cover and place the
gasket on the cover so that the bolts hold it in place while you
manoeuvre the cover into position. Using care, place
the timing chain cover up close to the bearing plate. Then manoeuvre the cover
so as to slip the lip seal over the end of the crank. Install and tighten the
bolts that attach the cover to the front bearing plate.
The order and
timing for installing the sump with its gasket and the cork gasket are
critical. Look at the sump gasket and note that the zig-zagged ends adjacent to
the cork gasket hang over the edge of the sump. This is important. As already
stated, it’s long been my belief that the majority of big oil leaks occur at
this point because these two gaskets are installed out of order, crushing the
ends of the sump gasket, thereby allowing oil to escape around the ends. If the
gasket ends don’t butt up against the cork gasket, a major leak is forecast.
This means the sump gasket must be installed before the cork gasket.
gasket itself can be installed improperly. The partial cuts at the ends of the
gasket are supposed to slip into the slotted openings in the bearing cap, but
not all the way. When the sump is installed and the bolts tightened, it
squeezes the gasket and pushes the ends all the way up into the bearing cap, but
not before. I have botched the job at earlier times by inserting the cork gasket
all the way up into the slot on one side, leaving the other side too short to be
squeezed up into its receptacle. In this instance, that the cork gasket appears
to be okay is an illusion because the sides of the slot hold it in place. To
preclude this from happening to you, mark the absolute centre of the bottom of
the cork gasket with a pen. Later, when inserting this gasket, check to make
sure the gasket is centred by checking the mark at bottom dead centre of the
With the cork
gasket marked but not installed, it’s time to install the sump gaskets. Again,
lay out some newspapers and apply a liberal dose of high-tack sealer to only one
side—the side that butts up against the block. Leave the other side clean.
Apply the gaskets to the block. The high-tack sealer should hold them there. If
it doesn’t, pull them off and give them another dose of sealant. Eventually,
they’ll stick. With the sump gasket sticking to the block, insert the cork
gasket into the slot on the bearing cap. Check your mark to make sure it’s
centred. The sides of the slot should hold it there provided you’ve pressed the
cork well into the slot. The jagged ends of the sump gasket should now just be
nudging the cork seal. By the way, I wore surgical gloves while messing with
the high-tack gasket sealer.
With both gaskets in place, grab the can of high-tack and spray the underside
of the sump gasket...liberally. Some haste is required as you don’t want to let
the upper side of the sump gasket to dry out. Now, you’re ready to reinstall
the sump itself. When that’s done, you’re almost through. Don’t forget to apply
a dab of silicone sealer in the slot at the front of the sump where the lip seal
will sit. With the sump in place, the crank pulley should slide right through
the lip seal ready to be tightened down. Remember the washer that goes between
the nut and the pulley. Reinstall the radiator, shell and connect the hoses and
you’re done. Don’t forget the bolts that attach the sump to the transmission
note on oil leaks. Never, never remove the banjo bolts that connect the oil
lines to the filter and block without replacing the copper washers that go on
both sides of the banjos. In tightening these bolts, old copper washers can
shred bits of copper off and cause leaks.
recommend warming up the engine two or three times and checking for leaks before
hitting the road. Run it up and let it cool down, all the time checking for the
odd leak. It’s almost certain that you’ll find several timing chain and/or sump
bolts needing an extra turn.
I made all the foregoing mods
to Abbie. No oil leaks up front. Maybe a tiny drop at the rear after a very
long, hard run—if that much. As my granddaughters like to say, “That’s cool,
Bop Bop.” Hallelujah!
Archimedes - Type Rear
by Chris Nowlan
Perhaps the most annoying source
of oil leaks in older British sports car engines is the mechanical oil
slinger/seal arrangement designed as the primary rear crankshaft seal. The
theory of this Archimedes-principle seal, is that the spiral grooves at the back
of the crank fit with only a slight clearance to the stationary upper and lower
oil control surfaces. As the crankshaft rotates, the action of the reverse oil
control threads against the flat sealing surfaces draws the excess oil back into
the hollow cavity next to the rear bearing where the oil drains harmlessly back
to the oil pan.
In reality, this seal
arrangement works well as long as minimum clearances are maintained. A slight
amount of leakage is inevitable when the engine is shut down. This residual oil
drains through a small hole in the bell housing and should not amount to more
than a few drops escaping on to your driveway
Since the oil
control threads and the sealing surface are not supposed to wear, few workshop
manuals offer detailed instructions on the fitting of these seals nor quote
specific clearances. In studying engineering drawings for the T-series
crankshaft and rear main upper seal, factory clearances can be calculated to
0.0053" minimum to 0.0088" maximum. The MGA Workshop Manual specifies a total
clearance of 0.003" to 0.006". Although the T-series spec. seems overly
generous, the MGA spec. appears more reasonable and can be considered a guide
for all applications.
An expanded view of the scroll threads, with
Since the oil control threads
and the sealing surface are not supposed to wear, few workshop manuals offer
detailed instructions on the fitting of these seals nor quote specific
clearances. In studying engineering drawings for the T-series crankshaft and
rear main upper seal, factory clearances can be calculated to 0.0053" minimum to
0.0088" maximum. The MGA Workshop Manual specifies a total clearance of 0.003"
to 0.006". Although the T-series spec. seems overly generous, the MGA spec.
appears more reasonable and can be considered a guide for all applications.
The sealing surfaces (and, to a lesser extent, the oil
control threads) will wear if the rear main bearings become excessively worn or
if the block alignment becomes distorted. Leakage problems can also result from
inaccurately refitting the replaceable sealing surfaces used on many British
sports cars. Jaguar and TR2-4A used replaceable upper and lower seals,
Austin-Healey 100-4 and MG TC-TD-TF used only a replaceable upper seal while the
MGA and 6 cylinder Healey incorporated sealing surfaces cast integrally with
both the block and rear main cap.
In renewing this critical seal, a number of alternative
techniques can be employed. Perhaps the most foolproof and effective method is
to have your block and the sealing surfaces line-bored by a competent machine
shop. By carefully measuring bearing saddle dimensions and/or the diameter of
the oil control threads, correct oil seal diameters can be determined. This is
a fairly expensive operation but is the only way to restore non-replaceable
sealing surfaces. (MGA owners take note, as this is a common problem!)
Replaceable seals can be hand-fitted with care and
considerable patience. The crankshaft and main bearings should first be
installed and checked for proper clearance using "Plastigauge", available from
any automotive machine shop. Also, check to be certain the crank rotates freely
and has proper end float, then remove crank and prepare to trial fit bolt-on
sealing plates. On MG TC-TD-TF blocks, remove the two small dowel pins, as
these would effectively prevent any adjustment in the location of the seal.
Install seal loosely, using appropriate gasket and gasket cement. Apply a thin
film of engineer's bluing (the thicker type sold in squeeze tubes is easier to
work with) to the sealing face. With the seal fixing bolts slightly loose it
should be possible to snug and center the seal against the crank. After
tightening up the seal, torque the lubricated crank assembly to full spec. Now,
carefully rotate the crank once or twice before removing the crank once again to
inspect the contact pattern on the seal. The ideal situation is to adjust the
seal so that you are left with a very thin film of engineer's bluing on the
sealing surfaces. Particular attention should be paid to the upper sealing
surface on the block as these are most subject to wear and are consequently most
In some cases, it may be necessary to remove some material
from the parting face of one or both seals. This must be done carefully; lay
sandpaper on a dead flat surface or pane of glass to help insure accuracy. It
maybe necessary to remove and refit the crank five to six times to insure that
you have achieved a correct fit. A certain degree of light contact is not
generally objectionable, particularly with the replaceable aluminum seals, as
these will bed-in as soon as the engine is started. Heavy contact that makes
the crank difficult to rotate could, however, cause serious problems. The small
dowel pins originally used with the T-series seals are not really required and
their reinstallation can cause distortion and/or a shift in location of the
plate. If these pins are reinstalled, recheck your work once again.
Once the seals have been
installed, checked and rechecked, assembly can continue but may require that the
crank be removed once again in order to install connecting rods and pistons
(Remember folks, patience is the ultimate virtue!). Last, but not least,
particular care should be exercised in installing the oil pan together with all
appropriate gaskets and seals (See “How to Stop (Almost All) Oil Leaks in Your
T-Car The Cheap and Easy Way” by Skip Burns).
hand fitted and determined with all certainty that you have achieved a correct
fit, your rear main seal should be nearly 100% drip free. A last word of
advice: be sure that your crankcase breathers are clean and free of obstruction
and that your gearbox first motion shaft seal is in good order. A problem in
either can otherwise mask over a job well done.
Oil Seal by GM
The “Moss kit” SOMETIMES works. I know many people who
have had great successes with them and consider them the best thing since sliced
bread. I also know many people who have poured countless hours and quite a few
dollars trying to get the Moss kit to work, the results still being toasted
seals and oil leaks. I went through two Moss seals and an additional Viton seal
with no long term success, even though the seals were installed with less than
0.002" of run out and perpendicularity within 0.001", with a micro polished
crank flange! The fault is not with the design, or the installation procedure.
The problem comes from the seal itself.
The problem is that the seal was not designed for a shaft
of not quite 4 inches to be spinning at something around 4000 rpm*. Go down to
your local industrial bearing supply house and look at the specifications in the
front of a CR or National Seal catalog, do the calculations, and you'll see that
such an installation is at the ragged end of acceptable use for those seals.
Taking into account the not-so-perfect surface condition of the flange and the
non-NASA concentricity of the carrier arrangement, it is no surprise that a
large percentage of them cook within 1K miles.
Now the good news. If you are considering installing a
Moss kit, you are already looking at pulling the engine out, partially
disassembling the little beggar and using up half of a gasket kit. With a bit
of disassembly, a trip to your local machine shop, and a $6-$8 part, I can
virtually guarantee you won't leak again! The answer comes in the shape of a
rear main seal for a small-block Chevy (Gag! Choke!). Fork out the big $2 more
for the heavy-duty silicone one. Fel Pro: BS 40013 or equivalent. This is a
split seal that even has nifty little ridges that act like the old Archimedes'
screw to wipe extra oil away from the sealing lip so that it lasts even longer!
The process is simple. Tear your engine apart (Go ahead.
You know you want to...). You can have a good look at your rings and bearings
while you're at it. Take the nice clean block, the rear main cap, the top half
of that silly slinger arrangement and your crank down to your local machinist.
Doesn't have to be an automotive one. It might even be cheaper to go to a good
job shop. Bolt up the rear cap and the slinger plate to the block. Make sure
that the pins fit well. Have the machinist set the block up on his mill or
boring machine, dial it in off of the bearing I.D., and make three cuts (You can
get exact dimensions from any shop that does Chevy engines, you can measure a
Chevy block, or you can just get the machinist to do the measurements then and
there.). You will want to open up the bore of the screw surface to fit the
diameter of the groove on the outside of the new seal. Then take two facing
cuts, on the front and on the rear of the old slinger to make a flange of the
correct width to hold the new seal. That's half the job.
Mount the crank in a lathe or crank grinder, and turn the
old scroll surface down. A low penetrating weld bead might be beaded, to build
up the LD. surface to that required for the new seal. Final diameter is same as
a small-block Chevy. You can even remove that little slinger disc part ahead of
the scroll, too. Finish it to a good micro-polish and its done. I don’t
consider it too blasphemous to cut original parts in this manner. They never
really worked anyway...**
Clean the block, gather up a new set of gaskets, bearings,
and what have you, and assemble as you would normally, with the following
considerations. Don't bother with the paper gasket behind the slinger plate. A
thin film of silicone behind it will do the job better. Press half of the seal
into the block half of the new, flange before dropping the crank in. Press the
other half onto the new flange on the main cap. A dab of silicone between the
two surfaces will seal them together, but don't silicone the mating faces of the
split seal. It is meant to go together with a bit of a crush.
This may sound like a daunting task, but it sounds much
more complicated than it really is. The machine work is extremely straight
forward for any competent machine shop, and it should cost about half of what
just buying a Moss kit does. You will end up with a modern seal doing exactly
what it was designed to do, in the environment in which it was meant to do it.
It is also running at a fraction of the surface speed of the Moss arrangement,
so wear is hardly an issue.
*The Moss seal is using a different seal now that purports
to have corrected this problem, see the article titled "Improved
Moss Oil Seals".
have to disagree with this statement, as the original system worked relatively
well in the cars since 1939 and still works very well in our TD
- Dave DuBois.
Oil Seal Part Numbers
|Volvo cam oil seal P/N 6842273
|Moss P/N 120-750
|Chicago Rawhide P/N 13537
|or P/N 36x47x7
If the portion of the crankshaft pulley where the seal
rides is worn, Chicago Rawhide supplies a product known as a Speedi-Sleeve, P/N
99138 that can be fitted to the pulley to make the seal fit correctly.
Note: the Chicago Rawhide P/Ns may be prefixed with CR.
Moss Oil Seals
Subject: From Al Moss re Oil Seals
A message to T-Series owners everywhere:
It has been over seven years since I first started
manufacturing and selling the Moss Oil Seal Kit and total sales are rapidly
approaching 2000. True, there have been some problems and some articles have
appeared worldwide "bad mouthing" my Kit.
The "problems" stem from three sources:
1) We are working in an area of the engine that was not
designed with any precision or consistency by the factory.
2) Many "mechanics" refuse to carefully read and follow the
instructions provided with the kit, and finally.
3) The seal provided in the Kit (Chicago Rawhide #37388)
was not designed for the RPM and temperatures encountered in some T-Series
engines. This notwithstanding, they _do work, even in racing engines.
One of the many advantages of my Kit is that no
modifications to the major engine components are required, unlike the very
major modifications required by other installations, many of which still leak!
I am proud and happy to announce that I have been working
with Chicago Rawhide since last year and we have come up with a new and vastly
improved oil seal to replace the 37388. While the dimensions of this new seal
are the same; the improvements are:
1) The seal is made of graphiteimpregnated Teflon, the
finest seal material known.
2) The seal is rated to 12,000 RPM, a figure reached by
very few T-Series engines:
3) The seal is rated to 600 degrees F.
4) The lip of the seal has been moved back to insure better
contact on the surface of the crankshaft flange, and,
5) The lip of the seal has a reverse spiral to control the
flow of oil.
All Kits supplied henceforth will include this new seal. I
can supply this new seal for $26.00 (price correct at time
of printing) ppd.
1015 Soldier Pass
Sedona, AZ 86336
Rear Engine Oil Seal (Otherwise known as “If it
works, leave it alone”)
by John Seim
Recalling those words of wisdom, I took a hard look at
both the Moss Oil Seal, and the GM rear oil seal. I looked at the MG engine
block, and wondered, "Why would MG (Morris) put a seal in the back of the engine
that didn't work?". Then it came to me. Morris put a rear oil seal (Thrower
Plate) in the back of the engine. This design dates back to the mid-thirties,
but probably was part of the Continental engine design, when the engine was
initially designed, in the late tens. It worked well at that time (the tens),
it just wasn't state-of-the-art in the post-war years.
What they incorporated in their
design, was an Archimedes screw to return the oil back into the block, that had
worked it's way to the rear-most portion of the crankshaft. The Archimedes
screw is at the back of the crankshaft, then an oil barrier (plate), then the
large flange for the flywheel mounting. In the engine block, at the back of the
rear main bearing cap, was a flange lip that would surround one half of the
Archimedes screw. The thrower plate mounts directly to the rear of
the block. It supplies the other half to surround the Archimedes screw. The
thrower plate butts up to the bottom of the rear main bearing cap, and is
secured by two pins and by three 6mm x 1.0 bolts. The design worked reasonably
well, as long as the clearance between the Archimedes screw and the rear main
bearing cap/ thrower plate was kept to a minimum.
What happens is that the
crankshaft flexes. Remember, these weren't balanced crankshafts, or flywheels,
or other moving parts. A small amount of unbalanced weight, over the years,
moves the part in an elliptic, rather than a circular motion. Add the weight of
the flywheel attached to the rear of the crankshaft, and you can either increase
the unbalanced weight ( if both unbalanced weights are placed on the same side)
or move the imbalance by installing the flywheel having a greater imbalance that
that existing in the crankshaft, to the opposite side of the crankshaft's
imbalance. In any event, the wear at the rear main bearing is greater than
either the centre or front main bearings. This wear
allows for the Archimedes screw to move outward into the circular surfaces of
the rear main bearing cap/thrower plate, enlarging the opening. With a larger
opening (clearance), the Archimedes screw becomes inefficient. No where in the
workshop manuals does it mention to check clearance at this point. Jim Bigler,
Jerry Felper, and others knew that the thrower plate had to be butted against
the rear main bearing cap. In fact, they would advocate removing the two pins,
and tap the thrower plate up against the rear main bearing cap, with the cap
torqued to spec to the engine block. Bud Quist took this one step farther. So,
what's the solution?
Have all parts of the engine balanced. Then, mount the
rear main bearing cap to the block, torqueing the nuts to spec. Install the
thrower plate, using the three bolts and the two pins (I would remove and
discard the pins. D. DuBois), plus the gasket, and gasket cement. Do not
tighten snug the bolts. Tap the thrower plate at the left and right pin
corners, to butt the plate to the rear main cap. This also bends the pins,
helping to keep the plate against the rear main cap. With this completed, now
tighten the three bolts snug.
Smear a thin coat of J-B weld on both of the
Install new main bearings into the engine and main
Using Teflon tape, wrap two
turns around the Archimedes screw portion of the crankshaft. Press the tape
into the screw threads. The Teflon tape acts as a
release agent, and helps to remove the J-B weld from the screw threads.
Lay the crankshaft in the block.
Install and tighten to spec the
centre and rear main bearing cap.
Rotate the crankshaft in the direction that it spins,
two or three complete revolutions.
Remove the centre and rear
main bearing cap.
Remove the crankshaft. Pull the
Teflon tape out of the threads. Use a dental pick, or other tools, and
remove any remaining J-B weld residue.
Remove any excess J-B weld in the rear main bearing cap,
oil thrower, or engine, not on the circular surfaces.
Let J-B weld sit for 24 hours.
Repeat steps 4-10.
the repair of the circular surfaces. The Archimedes screw now has a minimum
clearance to work with. When assembling the engine, place some gasket cement on
the flat surface of the oil thrower. This seals the circular area. Almost all
oil will now be returned to the engine. You will have a small leak, better than
when the engine was new. The cost of this repair is about $5.00.