A 'spheroid cast iron' overhead camshaft
operated by a timing belt.There are the same number of suitably positioned
cams as there are valves to operate; at the front, it is prepared
for the fitting of the toothed pulley, through which the motion
of the crankshaft is received, by means of a suitably tensioned
belt (see 'repair procedures' section).
1, Camshaft oil seal2, Camshaft3, Tappet adjustment shim4, Tapppet5, Cotters6, Upper shim7, Spring8, Oil seal9, Lower shim10, Inlet valve11, Exhaust valve12, Valve guideThe camshaft is the component which, through
the cams, opens the valves for the required time. Since in 4 stroke engines the working cycle
takes place during two revolutions of the crankshaft, whilst the
valves have to open only once during the cycle, the camshaft only
has to rotate once; therefore, the toothed pulley fitted on the
camshaft will have twice the number of teeth as the pulley fitted
on the crankshaft.
