DETROIT DIESEL 53
PISTON AND PISTON RINGS
The trunk type malleable iron piston (Fig. I) is plated with a protective coating of tin which permits close fitting, reduces
scuffing and prolongs piston life. The top of the piston forms the combustion chamber bowl and is designed to compress
the air into close proximity to the fuel spray.
Each piston is internally braced with fin-shaped ribs and circular struts, scientifically designed to draw heat rapidly from
the piston crown and transfer it to the lubricating oil spray to ensure better control of piston ring temperature.
The piston is cooled by a spray of lubricating oil directed at the underside of the piston head from a nozzle in the top of
the connecting rod, by fresh air from the blower to the top of the piston and indirectly by the water jacket around the
Each piston is balanced to close limits by machining a balancing rib, provided on the inside at the bottom of the piston
Two bushings, with helical grooved oil passages, are pressed into the piston to provide a bearing for the hardened,
floating piston pin. After the piston pin has been installed, the hole in the piston at each end of the pin is sealed with a
steel retainer. Thus lubricating oil returning from the sprayed underside of the piston head and working through the
grooves in the piston pin bushings is prevented from reaching the cylinder walls.
Each piston is fitted with compression rings and oil control rings (Fig. 1). Equally spaced holes are drilled just below
each oil control ring land to permit the excess oil that is scraped off the cylinder walls to return to the crankcase.
Inspect Piston Rings
When an engine is hard to start, runs rough or lacks power, worn or sticking compression rings may be the cause.
Replacing the rings will aid in restoring engine operation to normal.
Fig. 2 - Removing or Installing Piston Ring
Fig. 1 · Typical Piston Assembly
SEC. 1.6 Page 1