How to tell if the piston is installed backwards?



When installing the piston, you need to pay attention to the grooves and various marks on the top of the piston. For pistons with asymmetric grooves on the top, it is a simple way to judge the grooves corresponding to the intake valve. The common way of marking pistons is arrow and EXH, the arrow points to the front of the engine, that is, the side where the crankshaft pulley is installed, EXH stands for exhaust, which is the groove for the exhaust valve.

The piston is a reciprocating part in the cylinder block of an automobile engine, and its basic structure can be divided into a top, a head and a skirt. The top of the piston is the main part of the combustion chamber, and its shape is related to the selected form of the combustion chamber. Gasoline engines mostly use flat-top pistons, which have the advantage of small heat absorption area. There are often various pits on the top of the diesel engine piston, and its specific shape, location and size must be adapted to the requirements of the diesel engine's mixture formation and combustion.

In order to increase sealing and oil distribution, the section of the piston ring is not rectangular, but trapezoidal, barrel-shaped, and even has cuts or gaps, which naturally recognizes the direction. Generally, the inner incision is down and the outer incision is up. Four-stroke engines can generally be installed in reverse, but the power is insufficient, the lubricating oil consumption is fast, the performance of the engine is degraded or even damaged rapidly.


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