With the renewed interest in supercharging the 'B' series
engine we have introduced
a specification of head developed to enhance the charcteristics of a 'blown'
engine.
The inlet ports are enlarged to increase gas flow, this is achieved with the
fitment of
bronze sleeves in the pushrod tubes adjacent to the inlet ports. 1.625"
inlet valves are
used.
The exhaust ports are increased in size and we fit
a large 1.44" exhaust valve. To ensure
the head works for forced induction the ratio of the exhaust to inlet valve
diameter
needs to be in the region of 90%. With a larger than standard exhaust valve
the chamber
wall acts as a shroud preventing exhaust gasses from exiting the cylinder
efficiently.
By carefully unshrouding the valve we have increased the flow capability of
the exhaust
to ensure all the higher pressure exhaust gas can both escape and help to
draw down
the next induction charge. All in all a cylinder head specification developed
solely for
forced induction engines.
