الفهرس 
REVIEW OF PREVIOUS WORK.Only 14 pages are availabe for public view
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Abstract
The present work gives a detailed study on the
·effect of valve tappet clearance and also the state of
the valves a~d valve seats on the perfonnance of the
four-stroke spark ignition engines. This was done by
measuring the pressure in the suction manifold of the
engine by the use of a pressure transducer and a cathode
ray oscilloscope. The power of the engine was consumed
and measured by a hydraulic dynamometer. The first set
of experiments was performed to show the effect of inlet
valve tappet clearance on the pressure in the suction
manifold. This was made by changing the inlet valve
tappet clearance several times. For each value of
clearance, the engine \1asrun at different loads and
speeds.
A pressure transducer was installed in the
suction manifold. The output of the pressure tra.nsducer
was connected to a cathode ray oscilloscope. The curve
which represents the variation of pressure in the
suc tion manifold against crank ang l.eallover the four
strokes of the cycle was traced and recorded on photos.
By comparing these photographs the effect of inlet valve
tappet clearance could be studied The second set of experiments was performed when
one valve (or both) is defective. This means that
leakage occurs through this valve (or valves).
In each case photographs of the pressure trace at
various loads and speeds were taken. Again by comparing
these photographs, the effect of the state of the
valves and the valve seats could be studied. Also, in
each case of valve tappet clearance or valve defect,
experiments were performed to measure .the effective
power and torque of the engine as we Ll.as its specific
fuel consumption at full load.
IvIathematical equation whicl...represents the
pressure variation with the crank degrees Was obtained
using the method of curve fitting for the experimental
results at the case of standard clearance at certain
load and speed.
It is,hoped that this equation can predict any
malfunction in either valve.