What is an
Blocks, Studs & Water
Spare Parts List One -
Attaching Parts, Seals & Gaskets
Parts List Two - Crankshaft & Cross-shaft
Assemblies and Chains
Parts List Three - Pistons & Liners
Spare Parts List Four -
Spare Parts List Five - Cylinder Head
Parts List Six - Ignition,
Spare Parts List Seven -
Engines for Sale and Used Parts
Cracked and Corroded Blocks, Studs &
a load of rot!
picture on the right shows an all too familiar
sight - an AC cylinder block, in this case a PVT
one, just about rotted out. And even this
is not the worst that we have seen!
How do they get
in this state?
The rot is
caused by electrolytic action which attacks both
cylinder block and head studs.
Specifically, as the block deteriorates, the top
surface of the block is rotted away making it
impossible for the head gasket to seal.
This allows water to climb up the head studs and
to emerge on top of the head, from where it
drops down the chain case into the sump.
The sealing surfaces of the cylinder lands are
also degraded and water enters the sump past the
liners, turning the oil to a horrible, grey
sludge. The second picture shows a
seriously corroded cylinder head stud.
Studs in this condition, as in the picture to
the right, frequently snap.
Starting at the beginning
It is a
complete waste of time rebuilding an AC engine
unless the cylinder block is in really good
condition, meaning that there is no corrosion
present and that all mating surfaces are both
uncorroded and flat. If this is not the
case, then remedial action must be taken to
avoid serious and expensive
a corroded block does not have to be scrapped. Even very dire blocks
can be retrieved cost-effectively. Our
water jacket conversions not only replace
rotted material with sound metal but
restore the mating surfaces to ensure that the
figure-of-eight gaskets and head gasket can
perform their functions efficiently once more.
And when it's
the water jacket replacement is complete, your
block can be returned you for rebuilding, or we
can complete the engine rebuild for you.
A badly rotted PVT block
head stud ready to snap
Removing the rot
first step in any water jacket replacement is to
remove the corroded water jacket and old head
studs and to fit thread inserts for the new head
studs where required.
Machining it flat
stage is to machine the mating surfaces of the
block and water jacket casting to ensure a
perfect fit. Once the jacket has been
fitted, its top surface and cylinder lands are
machined to the correct height, following which
the new housings for the cylinder liners are
matched to the originals.
two parts of the restored block have been sealed
and secured together, the final tasks are to
drill and tap the holes where studs will be
fitted and to install the new feed pipe that
carries oil from the main supply up to the
camshaft and rocker gear. The block and
sump may also be machined now if an oil seal
conversion is required.
Once the machining is finished, the
cosmetic work can begin, the two parts of the
conversion being blended together so that the
join becomes virtually undetectable, as shown in
the photograph below. Please note that no
digital re-touching has been employed to
disguise the join.
Following completion of
the first stage of the cosmetic work, the
restored block is pressure washed to remove
remaining swarf and aluminium dust. Final
cleaning and touches to the appearance of the
block are carried out when other mechanical work
is complete and the engine is ready for
assembly. The rebuild of the engine shown
on the right is about to commence following its
water jacket replacement. The
smooth-as-glass top face of the block is clearly
years we have progressively developed our
block restoration techniques so that blocks
that even we might once have dismissed as
beyond hope can now be salvaged and restored
to healthy life.
pictures below show one such block.
have a block that you think is a hopeless
case, give us a call - we may just have good
news for you.
Proven, Cost-Effective Technique
we cannot take the credit for inventing
water jacket replacement, we can claim to
have developed and refined the technique to
a high degree of reliability, attested to by
the numbers of converted engines providing
dependable service to their owners.
In addition to enabling
the mechanical function of an engine to be
appearance of the converted blocks, with
their near-invisible join, is such that
they are frequently mistaken for new ones.......high
The current cost of a
complete water jacket replacement is from
£2,000.00. For this your engine,
whether vintage, PVT or post-war, will
look as pristine as the one above, with
new water jacket with an almost invisible
join, new head studs and all other studs
fitted and/or replaced as necessary, plus
a new timing chain tensioner and HT clips
ready fitted. The water jacket
conversion is by far the most
cost-effective way to restore a corroded
block to reliable service. But why?
order to appreciate the cost-effectiveness
of our block conversions, one must examine
Repair of corroded block without a new water
blocks can indeed be repaired without
needing a new water jacket - it all depends
on the degree of corrosion present.
Small amounts of welding are possible in the
thicker sections of
blocks but should only be undertaken very
sparingly and by a highly experienced
welder. Welding of extensive cracks in
the thinner parts of the block, such as the
sides, should be avoided as the cracks can
spread all over the place and the block can
distort badly. Such welding is likely
to be expensive. Wrecking the block
can make it more expensive
still! Cracks large and small can
usually be dealt with successfully by
amounts of corrosion in the stud bosses may
be corrected by trepanning around the stud
and inserting a thick aluminium washer in
the trepanned hole. AC used to carry
out this procedure - whilst at the same time
trying to deny that their blocks suffered
head studs can be removed; sometimes but
very rarely do they just unscrew but more
likely a couple will come out and the rest
will either refuse to move or will snap off
where they enter the block. Studs can
be removed by using a succession of hollow
drills to bore downwards around the
stud. The stud can usually then be
unscrewed and the block repaired by
inserting tubes around the studs to fill the
drilled gap. This is a slow, tedious
and expensive process, the total cost of
which often exceeds that of fitting a new
water jacket, and one which still leaves
corrosion in the block to be
addressed. Such may entail
milling flat of the liner beds and top
surface of the block; this can lead to
serious dimensional problems at a later
stage. And more expense!
cylinder blocks have been available for a
little while now and this is a good
thing. However, they cost around
£5,000 each without VAT and there will be
further bills for line boring of the main
bearing housings to suit your particular
crankshaft. There are in fact very few
original blocks that cannot be retrieved,
thereby saving large amounts of money and,
importantly to some, the originality
and provenance of your car.
Cracking of the Cylinder Block
Cracking of the block
is sometimes caused by frost or by mishandling -
as in over-excitement at the throttle causing
the engine to blow up and the whizzy-round bits
to come out through the side - but there is
another, not widely acknowledged cause and that
is flexing of the chassis.
This phenomenon occurs
mostly in pre-war cars.
simply, the chassis bends and the engine,
effectively bolted almost solidly onto it via
its almost completely ineffective mounting
rubbers, tries to bend too but being a rigid
casting it cannot bend so it cracks
instead. AC were well aware of this
problem and in the late thirties revised their
engine mountings. Even so, the revised
version was less than perfect and by now the
rubber mountings have become flattened out, oil
sodden and inflexible lumps that can no longer
perform their function. Engine mounting
rubbers cannot be ignored, should be inspected
at least whenever the engine is removed and if
possible they should be upgraded as
A stitch in time
picture shows a block that has been cracked by
flexing of the chassis. A repair had been
attempted by welding up the crack on the inside
of the block. The weld has now been
removed and the crack repaired properly by
stitching, which can effect a highly secure
repair that can be made virtually invisible.
The stitching technique
can also be used to repair cracks and breakages
caused by frost or accidental damage; even when
whole chunks of block have been dislodged by
conrod or crankshaft breakage.
cracked PVT block
was repaired, the crack successfully stitched
and a new water jacket fitted.
The pictures above show just
a few of the thirty or so water jacket
conversions that we have carried out.