When installing a brand new piston, pay attention to the grooves and markings on the piston crown. For pistons with asymmetrical grooves on the crown, aligning the grooves with the intake valves is a simple way to determine the correct direction.
Pistons with a symmetrical crown design will have pre-set markings. A common marking is an arrow pointing towards the front of the engine, i.e., the side where the crankshaft pulley is installed. The letters EXH represent exhaust, indicating that this is the groove for the exhaust valve. The words LEFT or RIGHT only appear on non-inline engines, representing the left and right cylinder banks, respectively.
Understanding these piston orientation markings and carefully checking them during assembly will help avoid installing the piston backwards.
