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Detail for engine and drivetrain build up
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Stripping the engine
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Leading my ambition to use the original parts of my donor car, I am very eager to retain the original engine. To this end my
aim is to rebuild the engine myself. The plan is to strip it down to component parts and have the main components professionaly
re-engineered. Basically I plan to have the block rebored, fit oversized pistons and have the valve seats replaced for unleaded use.
While I have the engine in pieces I will also replace the oil pump, as failure of this component would have dire consequenses,
and renew the timing chain and tensioner.
With the exception of the removal and refitting of the gudgeon pins in the pistons, I should be able to strip and rebuild the engine
myself.
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The cylinderhead was removed and disassembled by removing the rocker cover and then unbolting it from the block.
Remember to loosen the nuts in the correct sequence to avoid distorting the head. I removed the rocker shaft complete and all the
studs were removed from the head and the block.
One good method of removing studs is to put two nuts onto the stud and hold the upper nut with a spanner
while undoing the lower nut. Once the two nuts are 'locked' together you can use a spanner on the lower nut to undo the stud.
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I wanted to remove the valves, but was unable to find a valve spring compressor which was strong enough. The compressor was
fitted over the valve, but provided insufficient leverage to compress the valve spring. Adding a lever to the compressor handle
allowed me to remove the first spring but distorted the tool so that it wouldn't undo any more. After thinking about this it,
occured to me that the problem may lay in the way the valve assemblis are held together. The valve goes through the guide in the head,
through the springs (they are double springs on the MGB) and through the spring cap. Two collets are fitted into a groove in
the valve stem and the spring tension forces the cap aginst the collets which are tapered. Each time the valve is operated
the collets are forced into the cap so after a period of time it would be likely that the collets and the cap will lock together which
would make removal difficult.
I decided to try and break the joint between the collets and the spring cap. To do this I placed a small block of wood under the valve
and placed a socket over the cap. A swift tap with a medium sized hammer, broke the joint and the springs subsequently compressed easily
with the valve spring compressor. The remaining valves were all removed. Finally with all the valves removed the head was cleaned up,
ready for the engineering shop.
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With the cylinder head removed I turned my attention to the engine block.The first thing was to turn the engine upside down and
stand it on a couple of wooden blocks to protect the top of it. This made the engine stable to work on. The front end of the block
was disassembled first. The fan and fan pulley were removed, then the water pump. I wanted to remove the crankshaft pully next, but
this proved impossible as I couldn't stop the engine turning against the spanner.
I turned my attention to the sump next. This was a simple enough job which consisted of removing all the bolts (I think there are
eighteen of them). Break the gasket seal and remove the sump. With the sump off I had another go at the crankshaft pulley. This still
proved to be very hard to remove, the bolt is 15/16" (the same as the rear hub nuts). To stop the engine turning
I wedged some pieces of wood between the crank case and the crankshaft, still the nut wouldn't release. Finally I applied some heat
to the bolt, and a large hammer to the spanner and managed to free it.
Next off was the clutch pressure plate and the clutch plate followed by the flywheel, the blocks were used again in the crankcase to
stop the engine from rotating and the six flywheel bolts removed. The front and rear engine plates were removed. The big end nuts were
released from each connecting rod (there are locking tabs that need to be flattened first), and the pistons removed through the top of
the engine (downwards as the engine was still upside down).The oil pump nuts were undone and the oil pump components were removed,
a lot of jiggling was required to do this.
The main bearing caps were removed by undoing the main bearing nuts, note that the front and rear caps require drifting out with a small
piece of wood and some gentle hammer work, and the middle cap has a threaded hole into which a bolt was screwed to aid the
process. The middle bearing also holds the thrust washers in place. With the Main bearings removed, the crank is simply lifted out.
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The last part to be removed was the camshaft. At first this caused me a problem as the distributor drive gear was still fitted
and I couldn't seem to get it out. This was resolved by a post to the NG owners club forum and was answered correctly by
Peter Bambrook, who guessed that I had forgotten to remove the retaining mechanism for the drive gear. With this removed the cam came
out easily. Lastly the block was cleaned ready for the engineering shop.
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All the cleaned components were bagged and labeled and loaded into the Jeep, ready to go off for re-engineering.
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Rebuilding the engine
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The engine was taken to a local engineering shop (Graham Roe Ltd in Fleet). Graham has a great shop there a traditional
enginnering shop with engine blocks and cylinder heads everywhere you look and the smell of engineering oil.
The crank was checked and found to be easily within tolerance so it was just polished, the Block was rebored and honed.
New pistons were supplied (fitted) to the con rods, new main bearings, thrust washers and big ends along with a whole
host of gaskets. The head has had valve inserts fitted for unleaded running.
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Working on the block the new pistons were dropped into the bores. Its important to fit them into the correct bores (those which they
came from) and also to have the pistons the correct way round. Each piston has the word 'FRONT' on its crown.
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A piston ring compressor is required to compress the rings sufficiently to allow the pistons to drop down fully into the bores.
Before applying the compressor set all four rings so that their gaps are at 90 degrees to each other. The compressor is wrapped
around the pistons and tightened and the piston can be pushed or tapped down into the bore.
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The block was turned over and the upper halves of the big ends and main bearings were fitted. these just push in. I smeared a drop of
oil on both sides of the shells before fitting them. Also the Thrust washers upper halves (the halves that do not have the tabs on
them) are slid round the centre journal. Note the oil grooves point away from the bearing towards the back and front of the engine.
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To complete the cranks installation the lower halves of the bearings and the caps need to be fitted. I fitted the second and fourth
main bearings first to locate the crank then I was able to rotate the crank and fit 1 and 4 cylinder big ends. Rotate the crank some
more and fit 2 and 3 cylinders big ends.
Once all the big ends were done, I fitted the remaining main bearings. The center bearing cap carries the lower half thrust washers.
All shells were smeared with oil both sides before fitting. Once all the bearings were fitted I torqued them up to 33 lb/ft for the big
ends and 70 lb/ft for the main bearings. I also bent the lock tabs over on the big ends. The rear bearing cap needs to be oil tight, so
a little joint sealer was applied to it when it was fitted.
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A new seal was fitted to the rear plate, which was then fitted to the engine using a new gasket and some sealant.
Note the addition also of the seal reatining plate. The engine is still upside down at this point.
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The camshaft is inserted carefully into the engine. The picture shows the crank sprocket and nut fitted,
but this is temporary to allow me to turn the engine.
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The front plate is added with a new gasket and some sealer, then the sprockets and timing chain are added.
NOTE it is very important to align the sprockets so that the alignment marks face each other.This ensures
the valves will open at the correct point in the engines working cycle. I used a new timing chain and tensioner.
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The timing chain tensioner is fitted, which can be a slightly tricky operation. The mechnism is a little like a retractable biro pen,
so the technique is to have the spring mechanism fully retracted in the locked position. There is a small plastic spacer that is clipped
in between the heel and the body which stops the unit from fully compressing. Fit the assembly complete with back plate to the
block then remove the spacer and fully compress the spring. This releases the mechanism.
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While the sump is off the crank and cam nuts are tightened to their full torque of 70 lbft. This is
easier with the sump off, because a wedge can be used inside the crank case to stop the crank turning. One thing that caused some
consternation was the oil thrower which fits on the crank shaft inside the cover. The manual stated it should be installed with the
concave side away from the engine, or with the 'F' marking away from the engine. As the 'F' was marked on the convexed side it was not
possible to fulfill both these requirements. I decided to use the 'F' marking. A new seal was pressed into the timing cover which was
then fitted to the front of the engine.
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Two problems emcountered at this stage. Firstly, the 'Red' lacquer I bought to paint the engine turned out to be flourescent pink!
(see photo). Secondly the sump wouldn't fit back on. After a bit of head scratching and a post to the NG owners club, I worked
out that the problem was the way I had fitted the studs for the main bearing caps.
The studs screw into the block and the caps fit over the studs. Lock nuts are used to bolt down the caps. The studs have a shoulder
about 1/2" in length. I had fitted this end outside the block whereas I should have screwed this end into the block.
The result of this is that the studs protrude further from the block and prevent the sump from sitting down on the block. I
refitted them the correct way up and the sump was then ready to fit.
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With the sump problem corrected I fitted a new oil pump and gaskets. The original oil pickup filter was used afetr a good clean
to remove 40 years of sludge.
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The sump was fitted, with a new gasket and new cork seals at each end.
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To complete the bulk of the bottom end rebuild a new oil pressure reief valve and spring were fitted.
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The sump and lower parts of the engine were painted (for the third time) finally I managed to get some red lacquer that was red!
The engine was turned over rightway up ready to receive the head.
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With the lower end fairly complete it's time to rebuild the top end. First job was to refit the valves.
The cylinder head had been overhauled by fitting new valve seats, this was necessary for running it on unleaded petrol.
The valve guides had been replaced, new Inlet valves were supplied also.
The valves were reinserted into the
same positions they were taken from, before fitting the springs the valves were ground into the seats to make a better gas seal.
This is done usine a coarse grinding paste initially then a fine paste to finish up. The paste is applied to the valve rim and
the valve insterted, then the valve is rotated back and forth using a grinding tool. A few back and forth motions are applied then
the valve is lifted and turned and the process repeated.
Once they are lapped in the valve spring compressor was used to force the springs down while the collets were fitted. Be careful
not to pinch your fingers when the compressor is released. The picture shows the head with all the valves refitted.
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The head studs were cleaned and refitted into the block, note that there are four long studs and seven short studs,
the long ones extend through the rocker shaft. The headgasket was dropped over the studs. The head gasket is fitted dry,
make sure it is the right way round and the right way up.
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The head was placed over the studs and the additional rocker shaft studs were fitted. These are slightly narrower than the
main head studs. Two are long and two are short, the long ones are fitted at each end, with the shorter ones towards the middle.
The long studs provide the fixings for the rocker cover.
The rocker shaft was disassembled, cleaned throroughly and reassembled.
There are small oil ways in each of the rockers and in the shaft itself, make sure these aren't blocked.
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The rocker assembly was dropped over the studs. Intitially all the nuts were tightened finger tight. Then they were progressively
tightened in three stages to the correct torque which is 45-50 lb/ft. It is important to follow the sequence in the manual as this
helps to ensure a gas tight seal, and helps prevent the head from warping.
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The side plates were fitted to the block, these use gaskets to make an oil tight fitting. The rockers were adjusted (a three handed job),
and the distributor drive spindle was inserted. When inserting the spindle it is important to ensure that it meshes correctly with the
camshaft drive gear. On the 18G engine, the drive spindle is inserted with the drive slot horizontal, and the larger segment to the top.
As the spindle is inserted the gears mesh and the spindle rotates, it should end up with the spindle at the two o'clock position. A
bolt is screwed into the drive spindle to make it easier to perform this operation. With the spindle inserted, fit the shaft locking
plate using the single countersunk bolt.
The water pumo and theremostat housing were fitted along with a new thermostat and the more painting was undertaken.
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The flywheel was fitted and torqued up usinng the six flywheel bolts. Remember to fit the locking plate and bend the tabs over
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Like Chris Humphries, I found that my universal clutch alignment tool wasn't universal. This is suprising as I bought it in
the late seventies and would have thought it would have been designed for the cars of the time. Anyway the problem was solved
by wrapping some masking tape around the end as this was too small for the spiggot, the plate centraliser was the correct size.
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With the tool corrected, the clutch was fitted. Make sure the clutch plate is fitted the right way round (one side is marged 'flywheel'.
One of the clutch to flywheel bolts sheered in the process, but luckily I was able to remove and replace it without taking the
whole clutch apart again.
Other than a little more painting and the fitting of the engine mounts, the engine is now ready for installation.
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Overhauling the Gearbox
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I have a choice of three gearboxes for my car, the original from the donor car, a spare that came with
the second hand body kit, and one that I bought early on thinking the original didn't have an overdrive.
Visually there's
not much to choose between them. None are obviously damaged, all have the best part of 40 years of grime on them, so I
decided to use the donor car box for the sake of originality.
To be honest, I think gearboxes are scary. So I plan to break it
down as little as possible, while cleaning it and replacing a few gaskets and seals.
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First I removed the selector linkage to allow access to the overdrive nuts and help with the cleaning, this may have been my first
mistake.
As soon as I loosened the 6 retaining bolts for the linkage housing a small peg and sping dropped out from somewhere, now I'll have
to find out where they go.
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The overdrive unit was separated from the gearbox. This allowed a visual inspection of the overdrive and makes it easier to handle for
cleaning and filter/seal replacement.
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All the parts were cleaned on the outside. The inside of the bellhousing was the dirtiest, I think that possibly the rear
engine seal has leaked in the past.
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While re-assembling the coponents I fitted a new front gearbox seal, this fits inside the front cover accessed through the bell housing.
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I also replaced the overdrive filter, the old one was very gummy, this picture shows the residue under the filter.
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And the rear overdrive seal.
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Re-assembly proved to be quite tricky. The overdrive has two components which fit over the splined gearbox shaft, so the splines
have to be correctly aligned, also the pump is operated by a cam which proved to be difficult to locate. Without everything being
aligned, the units would not mate fully. I found it useful to have a gear selected on the main box so that I could turn the input
shaft as well as the rear flange to jiggle everything into place.
The completed unit looks a lot smarter.
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Fitting the Engine and Gearbox
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With the main engine and gearbox work complete, it was time to fit the units onto the chassis.
The first job was to mate the engine and gearbox. The gearbox gearbox crossmember was attached to the gearbox mounts. On
the original MGB the gearbox mounting was a very complicated affair with crossmembers and two sets of rubber mounts(one square and one
round, plus an additional carrier piece. I'm pleased to say that the NG is a lot more simple. The square gearbox mounts (I fitted new
ones) are attached firstly to the gearbox crossmember using the single integral mount bolt. Next the mounts are fixed to the gearbox
using two bolts and spring washers each. I left a little slack on the bolts to allow for alignment. The front of the gearbox was rested
on a piece of wood to keep it clear of the floor.
The enigine was raised a couple of inches clear of the floor and the hoist was rolled towards the gearbox. It is at this point that
you find out whether you made a good job of the clutch alignment. The gearbox input shaft is located through the clutch and the two
units are pushed together.
I found that it was difficult to get the units to push together fully, but I think that the problem is one of manoeverability. So once
they were close enough, I fitted a couple of the bolts and pulled them up together by tightening the bolts.
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With the units mated, I fitted the engine mounts. Again there seems to have been a lot of variations on the originals with spacer plates
etc. but the NG was straightforward. The mounts were fixed to the engine first and were tightened fully. The engine and gearbox were then
lifted and the chassis was rolled forwards. The rear end of the gearbox was tilted downwards so that the gearbox crossmember tucked
underneath the chassis, and when the unit was roughly aligned I lifted the rear of the gearbox, and loosely fitted the crossmember to
the chassis from below. Note that there are two sets of holes that the gearbox member can use, the rearmost set are for units with an
overdrive and the front moust fixings for gearboxes without the overdrive.
The engine unit was now lowered and the four engine mount bolts used on each side to secure it to the chassis. The hoist was removed
and all the fixings were tightened fully.
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Although the engine and gearbox are installed there are still some other components to be added, and these are easiest fitted before the
bonnet panels and steering column etc are fitted.
First is the Clutch slave cylinder. This bolts on with two large bolts to the mounting on the gearbox bell housing. A new unit was
fitted as the old one had seized up.
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My second hand body kit, contained , among other things a canister type oil fiter adapter. The original MGB had the old paper type
filter. Unfortunately the adapter is one of the inverted type which tend to be messy, but I decided to fit it for now and will change
it later on some time when I perform a service.
The adapter was fitted with a new rubber sealing ring to the block and the canister oil filter was screwed on.
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