ENGINE
8
DESCRIPTION AND OPERATION
OPERATION
The K Series engine is built up from aluminium
castings bolted together. These consist of three
major castings; the cylinder head, cylinder block and
a bearing ladder which is line bored to provide the
main bearing bores. Attached to these are three
minor castings; above the cylinder head, the
camshaft carrier and the camshaft cover. Below the
bearing ladder is an oil rail.
Each of the ten cylinder head bolts passes through
the cylinder head, cylinder block and bearing ladder
to screw into the oil rail. This puts the cylinder head,
cylinder block and bearing ladder into compression
with all the tensile loads being carried by the cylinder
head bolts. Additional fixings are used to retain the
bearing ladder to the cylinder block, and the oil rail to
the bearing ladder when the cylinder head bolts are
removed.
The cross flow cylinder head is based on a four
valve, central spark plug, combustion chamber with
the inlet ports designed to induce swirl and control
the speed of the induction charge. This serves to
improve combustion and hence fuel economy,
performance and exhaust emissions. The twin
overhead camshafts are retained by the camshaft
carrier, which is line bored with the cylinder head.
Self adjusting hydraulic tappets are fitted on top of
each valve and are operated directly by the
camshafts. The camshafts are driven from the
crankshaft by a timing belt, belt tension being
maintained by either a manually adjusted tensioner
or, on later engines, by an automatic tensioner.The
valve stem oil seals are moulded onto a metal base
which also acts as the valve spring seat on the
cylinder head.
Carbon break type exhaust valves are fitted to later
engines; these valves can be identified by the
machined profile on the valve stem. The profile
removes any build up of carbon in the combustion
chamber end of the valve guide, thereby preventing
the valves from sticking. These valves should be
fitted as replacements to all early engines.
The stainless steel cylinder head gasket has
moulded seals around all coolant, breather and oil
apertures and has steel cylinder bore eyelets.
Compression of the gasket is controlled by limiters
at each end of the gasket.
The cylinder block is fitted with ’damp’ cylinder
liners, the bottom, stepped half of the damp liner,
being a sliding fit into the lower part of the cylinder
block. The liners are sealed in the block with a bead
of sealant applied around the stepped portion of the
liner. The seal at the cylinder head is effected by the
cylinder head gasket with the liner top acting as a
break between the combustion chamber and gasket.
The aluminium alloy, thermal expansion pistons
have a semi-floating gudgeon pin which is offset
towards the thrust side and has an interference fit in
the small end of the connecting rod. Pistons and
cylinder liners are supplied in two grades. Big-end
bearing diametric clearance is controlled by three
grades of selective shell bearing.
The five bearing, eight balance weight crankshaft
has its end-float controlled by thrust washer halves
at the top of the central main bearing. Bearing
diametric clearance is controlled by three grades of
selective shell bearing. Oil grooves are provided in
the upper halves of main bearings No. 2, 3 and 4 to
supply oil, via drillings in the crankshaft, to the
connecting rod big-end bearings.