RUBY RUNNING ROUGH:
It could be fuel or air and not necessarily timing. Advancing may might
mask the fault. Jets maybe. Check compression – could be valve leak or
stuck valve. If too advanced, will kick back on starter. Timing needs to
be adjusted by ear and checking the engine note and performance whilst
climbing a gentle hill. DA7C Techncal Forum evening March '24.
OIL PRESSURE: If you’ve lost
oil pressure
after a service and have tried all the obvious culprits – pump, drive
gear, woodruff key, pressure relief valve and pressure gauge, here’s
one you may not think of. There are 2 types of rear
camshaft bushes!
If you fit the wrong one for your crankcase, you can finish up with no
oil pressure. So check the rear bush to ensure it is a good
running fit on the camshaft and a close fit within the crankcase
avoiding oil by-passing the bush altogether. For 3-bearing
engines, check the oil feed pipe to the centre main is seated well and
not fractured. |
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OIL PRESSURE: The
"spit and hope" type lubrication of the Seven makes it most important
to keep a watchful eye on your oil pressure gauge. You will soon see
that when the engine is cold it swings off the scale but, as the oil
gets hot and thins, the pressure drops back to less than 5 lbs under
normal driving conditions. This is quite normal. However, when hot,
should it uncharacteristically rise dramatically,
immediate measures need to be taken. One of the most important items to
carry at all times is a length of 1/16th rod or stiff wire about 6-8
inches long. A sudden rise in oil pressure usually means that there is
a blockage in one of the
oil jets
supplying the big ends and, if left unattended, this would cause
starvation and big-end failure. These jets are covered by 2 small
brass bolts on the offside of the engine crankcase either side of
the oil filler tube. To clear a blockage, turn the crankshaft 1/4 turn
on the starting handle, undo the bolts and carefully poke the wire
down through each of the jets—it should go down about 3 inches plus,
(it may take a few attempts to get the feel of it and locate the holes,
why not have a dry run at home as practice?) This will ensure each jet
is free of obstruction. Replace the bolts and start her up and check
the gauge. Hopefully this will avoid an expensive engine rebuild!!
Gary
Munn |
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RE-FITTING PISTONS: When re-fitting
pistons—confused about the thrust side? Always re-fit pistons with the split skirt nearest the camshaft—sorted!
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GUDGEON PIN:Probably the worst disaster that can happen on your engine is to have a
gudgeon pin
clamp bolt work loose and come out. On its way out it will probably
bend the con rod, score the bore and break the piston. It will
drop on the gauze filter, be picked up by the crankshaft and smash a
star-like crack in the side of the crankcase. The answer to this is not
to use locking tabs but to ensure that you have new high tensile bolts
fitted with spring washers and do them up really tight using ‘Loctite’
etc. on perfectly clean threads. |
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OIL JETS:Jack French recommends turning the little
oil jets
that
squirt oil down onto the troughs in the crankshaft 20 deg towards the
crank centre-line (Mike Forrest says 30 deg, so take your choice!) to
increase the period during which the oil is squirting into the
troughs. I use a piece of hollow rod which fits over the jet and
bend it slowly. First clean up the ends of the jets where
previous owners will have walloped them trying to remove the crank and
after a gentle bending, test them by inserting a suitable piece of thin
straight wire to check alignment. |
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CLEANING: For
cleaning the waterways you can use a mild acid as found in brick cleaner or patio cleaners found at builders merchants.
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REMOVING CYLINDER HEAD:
When removing A7 low compression, 18mm,
cylinder heads,
to save hammering a screwdriver or chisel between the joint, try using
the hook end of a Ruby boot key into the plug holes of numbers 1 and 4
alternately. Even better, get 2 boot keys and make it even
easier. This dodge does not work for 14mm heads. |
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SUMP NUTS: In
replacing the sump, I’d fitted new set screws – those nice long-headed
ones with the oval washers. What I had forgotten, was that for the
centre rear one, you have to use a short one – otherwise, yes you’ve
got it, the tip just catches on the
starter ring…… |
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TIMING GEARS: Before undoing the
timing gears,
remove the fuel pump entirely from the crankcase and don’t replace it
until after the new gears have been firmly installed. If you don’t do
this, the camshaft may move backwards once the timing gears have been
removed allowing the petrol pump cam-follower (lever-thing) to slip to
one side of the pump-drive cam and jam things up! Even after re-fitting
the pump it will be judicious to check things are where they ought to
be by gently turning the crank by hand. If the cam follower has been
displaced, a firm ‘clunk’ can be felt as the crank hits the obstruction. |
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ALUMINIUM PULLEY: To release the large
aluminium pulley
at the end of the camshaft, hit it sharply sideways against the edge of
one of the holes so as to try to rotate the pulley on its shaft rather
than trying to hit it from behind along the length of its shaft. |
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CAMSHAFT BUSHES: Should you be building a 2-bearing engine from spare parts, make sure
you have the correct camshaft bushes
fitted at the front and back of the crankcase as there are two
different sizes: the earlier crankcases (with the starter inside the car)
have a smaller outside diameter for both front and rear bushes than later
engines (with the starter under the bonnet) and the front bush is also
slightly shorter. It is important not to confuse these with the ones fitted
to the later crankcases as they look the same to the naked eye. Should the
earlier ones be fitted in a later crankcase by mistake, there would be no
oil pressure as the oil would simply flow down the sides of the bush. The
inside diameters are the same on both crankcases. If in doubt, the bushes
should be a snug fit in the crankcase in both instances usually requiring a
light tap. Also check that you have the bushes the right way round as the
oil holes must align with the holes in the crankcase. Another useful tip is
to replace the square peg bolt that secures the front bush with a 3/16 inch
Whitworth bolt of exactly the same length, and then tap a 3/16 inch
Whitworth thread into the larger peg hole in the bush. This allows the bush
to be bolted up tight after assembly. Bolt the rear bush into the crankcase
first, making sure that you line up the oil holes, fit the front bush on to
the camshaft then “glue” the 9 centre rollers into their slot in the shaft
with grease and lower the assembly through the front of the crankcase taking
care not to dislodge the rollers, carefully lining up the front bush as you
lower it in so that the bolt holes line up. If you are lucky, the rollers
will slide into their cage first time but it could take several attempts!
Screw the new bolt and a fibre washer into the front bush - job done,
simple. If you are building the later 2 bearing engine, you will need the
camshaft with the extra cam to drive the mechanical petrol pump. The
3-bearing engine is different again, but that’s another story.
Glyn
Llewellyn |
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OIL
FILLER TUBE: So how
does one remove that thin-walled
oil
filler tube without collapsing it and rendering it useless? I managed to
find a piece of heavy gauge pipe which just fitted inside and after making
sure nothing nasty could drop into the engine and with pipe in place I was
able to unscrew the tube with an oil filter remover without crushing the
tube. Richard Bishop |
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CORE PLUGS:
If you are having problems getting your
core plugs to seal the following clever
solution was offered to me the other day. Soak some strands of string in
Hylotyte Red (replacement for Red Hermetite which is no longer available)
and roll into a sausage shape. Clean the recess in the head thoroughly and
allow it to dry. Line the inside edge of the recess with the wetted string
where the new core plug will bear and fit the core plug in the normal
manner. Tap it down with a suitable drift (suitable being about the same
size as the plug) until the domed surface is flat. Leave for 24 hours before
refilling or topping up engine with water. It should now be watertight.
Hylotyte Red remains flexible and is easier to remove than Red Hermetite.
“With
many thanks to ‘Bumbling’ of the A7OC”.
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THE CASTLEMAN CLIP:
When
I saw a trickle of oil from one of the oil jet plugs I just thought that the
plug had loosened as part of the settling-down process. But . . . you can
imagine my horror when I found that the thread in the crankcase was very
worn and quickly became non-existent after my attempts to tighten the plug.
The prospect of dismantling the engine passed in front of my horrified eyes
as this thread is (virtually) impossible to get at
with the cylinder block in place, and any swarf that dropped into the oil
gallery would have to be removed. So, after much head scratching,
wailing and gnashing of teeth I hit upon the idea of making a small clip that fits under the adjacent cylinder block holding down nut and presses
down on the top of the plug to stop it from being pushed out by oil
pressure. It might leak, but the plug would still be in place. This
was not difficult to make from a piece of flat steel, and I incorporated a
refinement into the basic idea by putting a small set screw and nut in the
outer end and allows adjustment of the force the clip applies to the plug.
In honour of the occasion, I call it The Castleman Clip. I inserted plug into
the crankcase using Loctite 2700 high strength thread locker, fitted the
Castleman Clip under the block bolt and tightened it down. Then I left it
overnight and, next day, started the engine with some trepidation. I need
not have worried! No leaks, engine running normally and oil pressure its
normal lofty self. Roger Bateman |
CRANKCASE/BLOCK
REAR NUTS: I always seemed to have difficulty getting the back
nut to the Crankcase/Block really tight, there seems to be so little room to
get a spanner on and or to move round. So my solution was to use one of the
'long' nuts from the tappet area (OK - I actually bought some more) to take the
top of the nut into an area where there was more room around the nut to get a
1/4" W - 5/16" BS ring spanner on. However, even then I had to thin down the outside of the ring to ensure
it went on OK. The photos show the difference in height.
With thanks to Sandy Croall (Cornwall A7C) |
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OIL PUMP:
When you assemble your oil pump
don't forget: radiused shoulders to the top, no gasket under the cover
plate. |
CYLINDER HEAD NUTS:
Use three or four steel washers under each nut on the A7 cylinder
head. With the washers in place, if a thread does strip all you have
to do is to remove the washers and use a new nut on the undamaged
part of the thread which had been covered by the washers. Presumably
the reverse is possible using washers to cover stripped thread so
that a nut can be placed higher up the stud on good thread.
Bart
Walsh Essex A7C
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CHECKING COMPRESSIONS:
Here is a simple test if you suspect your engine is low on compression
which will determine if it's your rings or valves, without having to
take the head off.
First remove the spark plugs and check the compression with a
compression gauge and take a reading, then put about a teaspoon full of
oil down the bore you wish to test, then put your compression gauge over
the spark plug hole crank the engine and take another reading. If the
compression increases, your rings are worn, if it doesn't it's your
valves. What the oil does is to form a seal around the top of the piston
so that compression is not lost down the sides. Do the same test on the
other three cylinders.
CRANKSHAFT
BEARINGS: The dual-purpose races at the front end of the
crankshaft
 should
be assembled with the faces marked " thrust " towards each other. When
the centre members of the races are tightened on the crankshaft, the
effect should be to hold the outer members together. A method of
testing is to grip the centre members in a vice, when the outer members
or tracks should be free; when wear has occurred, it may be possible to
pass a feeler gauge of .002 in. thickness each side between the outer
members. Should a feeler gauge .003 in. be accepted each side the races
should be renewed. The sketch shows correct fitting.
MODERN LIP SEALS:
fitting one of the modern lip seals with matching cover plate, available
from our usual suppliers, it will be noticed that comparing the new
cover with the old, there is no cut-away for the oil return to the
crankcase which, if you look with the cover off, is rear of the rear
main bearing outer at about 5 o’clock. Carefully mark the new cover
plate and file or grind the ridge on the plate to align with the oil
hole in the case - this will encourage return of the oil to the sump
when fitted. We always retain the oil dish thrower (outer dish towards
you). Do not over-paste the cover with sealant or the goo can creep and
block the oil return hole which, of course, you have previously ensured
is clear. Try the seal on the flywheel boss before fitting to ensure you
have the correct one and the boss is smooth. Apply a tad of grease where
the lip will seal. Gary Munn “Munwellyns”
CYLINDER HEAD NUTS: When nuts are tightened down,
the threads on both the stud and nut are stretched a little and it is
good practice to replace each nut not only on the same stud but also the
right way up. (Ideally, one should always use new nuts but ….).
Solution: drive 11/2“ nails 1/2
inch into a block of wood in the correct
pattern of the head studs and when removing the cylinder head pop each
nut and its washer on its correct nail and the right way up. As a bonus,
write the number of order of tightening the nuts with an indelible pen
beside each nail and the word “FRONT” just to be certain.
David Whetton DA7C (with apologies if every other owner wh has
already done this).
.jpg)
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FITTING EARLY
CAMSHAFT ROLLERS: Having trouble placing the rollers around
the centre
 bearing?
Even using grease, how often before getting them all in place one would
drop out and you have to start all over again. The worst part is the one
which drops out falls to the floor, gets covered in dust, and becomes
difficult to find or lost forever. It would be easier if the rollers
didn't end up on the floor. So here is a simple solution. Using a 2.25
ltr plastic drinks bottle, cut to a suitable length, place it round the
camshaft, and mount vertically in the vice. Then if you drop the rollers
they will be caught in the bottle. Vince Leek DA7C
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CHEAP PISTON RING
COMPRESSOR: An e asy
substitute ring compressor can be made up from a short piece of
rainwater pipe, and a couple of hose clips.
You need about 3 inches (75mm) of 70mm diameter UPVC rainwater downpipe
and two jubilee clips of a diameter in the 40-80mm diameter range.
Screwfix sell them in 10s, but it may work out cheaper to buy elsewhere
e.g. JIM’s or your friendly local garage.
Now the smallest Austin Seven cylinder bore is 2.20 inches diameter or
2.280 inches diameter absolute maximum oversize. This means you have to
reduce the PVC pipe diameter by cutting it along the length and removing
a strip about 20mm wide. A slit of that width will cover all bore
variants. All that remains to be done is to fit the clamp around the
piston, (using PLENTY OF OIL), tighten up the hose clips and insert the
pistons into the bore in the usual way. Provided you have oiled the
plastic sleeve there is no danger of the rings scraping shavings of UPVC
into the bores. Andy Tewel (Reproduced with permission of the
Cornwall Austin Seven Club).
FITTING CORDS PISTON
RINGS: New old stock Cords piston rings are for a Reliant
so there are only 3 rings per piston in the set - no scraper ring below
the gudgeon pin. The top compression ring supplied has a ridge dodger
step. I deglazed the bores before fitting the pistons from the bottom of
the cylinder, much easier than from the top as the bottom of the
cylinder has a chamfer to help ease the rings into the bore. Some people
have reported lack of power after fitting Cords rings, but my car seems
fine. I will discover how much the oil consumption has improved after
the next run. Roger Ballard DA7C
FITTING THE BLOCK: I
fitted the rings, pistons, conrods and baffles to the block, then stood
the crankcase on the flywheel end, the block is arranged on pieces of
wood to lift it level with the crankcase. The units are pushed together
until the rod big ends are inside the crankcase then fit the baffles
with a dollop of grease. Finally, continue pushing the block and
crankcase togeth   er
and bolt up. Geoff Kingsland DA7C
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