What is meant by the term valve lead in the motor industry?
The term "Valve Lead" best describes the amount in degrees in
which a valve will open before its desired stroke begins The
amount of Valve lead can be influential in the amount of air being
drawn into the engine. If the inlet valve is opened before the
piston has reached TDC on the exhaust stroke it will increase the
amount of air going in for the induction stroke. This is
also true if the Exhaust valve is opened before BDC on the power
stroke the exhaust gases will get a head start in leaving the
cylinder allowing more space for inlet gases to enter.