Specifications

ENGINE
already very good and no further balancing is
required. If the crankshaft is not as new, lightly
polish the journals with a suitable grade of
crankshaft finishing tape. Thoroughly clean the
component with petrol or other suitable solvent.
Blow out the oil passages with compressed air
prior to reassemble. The main bearing shells and
bolts are as production.
PISTONS AND CONRODS
To give the correct increase in the compression
ratio and increased durability, Cosworth, full
skirt, forged pistons are supplied. These have a
lighter gudgeon pin which is a pressed fit into the
small end bearing, as in the normal production
condition. The Cosworth pistons are sized to be
compatible ONLY with the standard production
bore dimensions. These are in fact graded, but
the increased operating clearances with the
Cosworth piston easily accommodates any slight
variance in bore size.
The Cosworth piston is a direct replacement
for the standard unit, which can be discarded.
Circlip grooves are evident around the gudgeon
pin housing on the Cosworth piston, these must
be completely disregarded as circlips are not
required for this application. As a precaution the
conrods should be crack detected after the
standard pistons have been removed and prior to
assembly with the replacement pistons.
However, both the removal and fitting of the
pistons to the conrods is a specialised operation
and must be carried out by appropriately
qualified and equipped personnel. Heavy duty
conrod bearing cap retaining bolts are supplied
which also give more positive bearing cap
alignment.
The pistons have a designed `deck height' to
give a compression ratio of approximately
11.4:1, and when installed should protrude
above the block face at top dead centre by
0.4mm. plus or minus 0.10mm. (0.016ins, plus
or minus 0.004ins.) This dimension should be
checked in case of block discrepancies.
ENGINE BLOCK
78.995mm. to 79.025mm
3.11ins. to 3.1112ins.
CYLINDER HEAD ASSEMBLY
The bore size must be standard to remain within
the 1600cc maximum capacity limits and should
therefore conform to the following dimensions.
An oversize, competition piston has not been
developed. Prior to assembly, deglaze bores to a
micro finish and 45 degree hatch pattern. The
take-off hole for the standard engine breather
tower assembly, situated on the inlet side of
the block, must be blanked off with the plate
supplied. See photograph for the detail. Assemble
i n accordance with normal build procedures.
Carefully dismantle the cylinder head, placing
each component in numbered removal order so
that the parts required can be reassembled in
their original positions.
Prior to further cylinder head preparations,
a modification to give increased oil supply to
the hydraulic lifters, thus ensuring adequate
oil pressure under high oil temperature and
sustained high engine speed operating conditions
MUST be carried out. The oil pressure feed hole
i n the cylinder head casting, situated at the
exhaust side of the cylinder head face should
be increased in diameter. This operation requires
extra care, and entails drilling out the existing
, angled' 2mm. hole to 3mm. The hole must be
enlarged throughout its depth (approximately
40mm.), until it joins with the larger diameter
part of the `gallery' section, taking extra care
to follow the path of the existing `angled'
hole. Make sure that the oil passages do not
contain any residual swarf after completion of
the modification. Follow standard procedures
for cylinder head refurbishing.
The production Nova/Corsa 1600 engine
features exhaust gas recirculation. This is part
of the emission control system, where regulated
quantities of the exhaust gasses are recycled
through the inlet tracts under certain throttle