How many connection methods are there between the piston pin and the piston and connecting rod?
2 Answers
There are two connection methods between the piston pin and the piston pin bore: 1. Full-floating type: Under the normal operating temperature of the engine, the piston pin can rotate in both the connecting rod small-end bore and the piston pin bore, resulting in minimal and even wear. This method is widely used. To prevent the pin from moving axially and scratching the cylinder wall, circlips are used to secure both ends of the piston pin bore. 2. Semi-floating type: The pin is fixed at one location (either the pin bore or the connecting rod small-end) and floats at the other. Here is some additional information: 1. Introduction: The piston pin is a cylindrical pin installed in the piston skirt. 2. Function: Its middle section passes through the connecting rod small-end bore to connect the piston and the connecting rod. Its role is to transmit the gas force acting on the piston to the connecting rod or to allow the connecting rod small-end to drive the piston in motion. To reduce weight, piston pins are generally made of high-quality alloy steel and designed as hollow structures.
With decades of experience in the auto repair industry, I can tell you there are mainly two ways piston pins connect pistons and connecting rods. One is the full-floating type, where the pin rotates freely in both the piston bore and the small end of the connecting rod, usually secured with retaining rings at both ends. This design ensures more even wear and smoother engine operation. The other is the semi-floating type, where the pin is typically riveted to the connecting rod and doesn't rotate—it's fixed into the piston bore during assembly. While this method is sturdy and durable (common in old American big-displacement engines), it's prone to wear and may produce clicking noises. Full-floating pins are more common in high-performance cars as they reduce friction and extend lifespan, though they come at a higher cost. During maintenance, always check the retaining rings—if they loosen, replace them immediately to avoid damaging the entire piston assembly.
