What is an AC Engine?
Blocks, Studs & Water Jackets
Spare Parts List One - Attaching Parts, Seals & Gaskets
Spare Parts List Two -
Crankshaft & Cross-shaft Assemblies
Spare Parts List Three - Pistons & Liners
Spare Parts List Four - Sump Assembly
Spare Parts List
Five - Cylinder Head Assembly
Spare Parts List Six - Ignition,
Spare Parts List Seven - Water Pumps
Engines for Sale and
and Corroded Blocks,
Studs & Water Jackets......
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!
do they get in this state?
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.
at the beginning
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 disappointment.
corroded block does not have to be scrapped.
Even very dire blocks can be
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.
when it's done?
the water jacket replacement is complete, your block can be returned you
for rebuilding, or we can complete the engine
rebuild for you.
rotted PVT block
Cylinder 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
Machining it flat
next 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
Fitting it out
the 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.
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.
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 shown.
the 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.
you 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.
addition to enabling the mechanical function of an engine to be restored, the
appearance of the converted blocks, with their near-invisible join, is
such that they are frequently mistaken for new ones.......high
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 the alternatives:
Repair of corroded block without a new water jacket
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 stitching.
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 from corrosion!
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
and its causes
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.
phenomenon occurs mostly in pre-war cars.
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 well.
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.
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.
A badly cracked PVT block
block was repaired, the crack successfully stitched and
a new water jacket fitted.
pictures above show just a few of the thirty or so water jacket conversions that we
have carried out.