ENGINE
EA330-E4, WSM
1-M7
[5] PISTON AND PISTON RING
Since the piston is always subjected to high
temperature and high pressure and reciprocates within
the cylinder, it must be lightweight, tough, heat resistant,
wear resistant, and of little thermal expansion. For this
reason, the piston is made of High-silicone (aluminium
alloy).
The piston crown is flat-formed. Grooves are formed
around the piston crown and these aid heat dissipation
and prevent scuffing of the piston and cylinder liner.
The piston has three piston rings.
The top ring (1) is of a Keystone type to prevent gas
leakage, and it designed for a better initial fit and to
prevent abnormal wear and seizure. The ring surface is
hard-chromium plated for improved wear resistance.
The second ring (2) is an under-cut type which
effectively prevents the rise of oil.
The oil ring (3) has chamfered contact faces and an
expander ring, which increase the pressure of the oil ring
against the cylinder wall.
A portion of the scraped oil is forced inside the piston
as it passes through escape holes in rings and piston.
These oil rings are plated with hard chrome to give
increased wear resistance.
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[6] CONNECTING ROD AND CONNECTING ROD BEARING
The connecting rod (2) is made of I-shape forging of
carbon steel so that it can withstand large repetitive
impacts.
The big end of the connecting rod is of a horizontal
split type and tightened with special screws. Since the
connecting rod body (2) and cap (4) are I.D. machined
after matching, matching must not be changed.
The crank pin bearing (3) is a split type, and made of
copper-lead alloy (called Kelmet) (with a mild steel back
metal). The surface is tin plated to obtain a better initial
fit.
The piston pin bushing (1) is made of lead bronze
(with a mild steel back metal) which has the most
excellent shock resistance, load resistance and heat
resistance. The surface is tin plated.
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(1) Top Ring
(2) Second Ring
(3) Oil Ring
(1) Piston Pin Bushing
(2) Connecting Rod
(3) Crank Pin Bearing
(4) Connecting Rod Cap
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