What are full-floating piston pins designed to allow motion between?

Full-floating piston pins are specifically designed to permit relative motion between the piston and the small end of the connecting rod. This design allows the piston pin to rotate freely within the piston while remaining secured in the connecting rod. This arrangement is critical in high-performance engines, where the interaction between the piston and connecting rod must accommodate thermal expansion, wear, and various load conditions during operation.

By allowing this freedom of movement, full-floating piston pins help to reduce friction and wear at the contact surfaces, which can enhance the overall efficiency of the engine. Additionally, this configuration accommodates lateral forces exerted during the engine's power stroke, ensuring smoother operation and improved durability of the engine components.