When installing piston rings, the material and direction of each piston ring with relevance to the piston head is important; otherwise the engine will not operate correctly, while severe damage may occur after long-term usage. Piston rings having a "TOP" mark or dot on the side of the piston ring must always be installed with the "TOP" mark or dot towards the top of the piston. Piston rings having no dots, bevels, or grooves can be installed either way. However, it is possible that piston rings requiring to be installed with specific direction do not have any marks. In addition, each piston ring should be installed at specific groove of the piston.
Below we provide some useful tips regarding the appropriate direction and piston groove each piston ring should be installed.
Torsional Piston Rings
There are two styles of torsional piston rings with inside bevels: top inside bevel and bottom inside bevel.
Scraper Piston Rings
Piston rings with a groove in the outside diameter must be installed with the groove toward the bottom of the piston. Typically, a scraper ring is installed at the piston groove right before the oil control ring.
Oil Control Piston Rings
Things are not so complicated with oil control piston rings, as these piston rings may have bevels only, which must be installed with the bevels toward the top of the piston. Oil control rings with spring coil are normally installed on diesel engines. In case of double beveled oil control piston rings, no specific direction applies. The pistons of the majority of engines take just one oil control ring. However, there are pistons which take two oil control rings. In this case, the oil control ring with spring coil is installed at the first piston groove for the oil control rings.
Top Piston Groove
Chrome-plated compression piston rings should be always installed at the top groove of the piston. In general, chrome-plated piston rings are typically not appropriate for air compressors, unless otherwise specified by the machine manufacturer, and engines equipped with Nikasil or chrome-plated cylinders.
Piston Grooves for Compression Piston Rings
If the piston has two grooves for compression piston rings, the scraper piston ring is installed at the second piston groove. If the piston has more than two grooves for compression piston rings, the scraper piston ring is normally installed at the piston groove just before the oil control piston ring. Some manufacturers for air compressors recommend scraper piston rings for all grooves of the piston.