🔍 Key Concepts

• Thermal expansion properties of aluminum versus cast iron • Why piston-to-liner clearance is needed in a cold engine • How clearance must change so that at operating temperature the piston runs correctly in the liner

💭 Think About

• Does aluminum expand more or less than cast iron when heated, and what does that mean for how tight or loose it can fit when cold? • If a metal will grow more as it heats up, should you start with a larger or smaller cold clearance to avoid seizure at operating temperature? • Which answer choice best reflects the need to prevent the aluminum piston from scuffing the cylinder wall as it reaches normal running temperature?

✅ Before You Answer

• Be clear which material has the greater coefficient of thermal expansion (aluminum vs. cast iron) • Visualize the piston at full operating temperature: will it be closer to the liner or farther away than when cold? • Check that the chosen option would reasonably prevent metal-to-metal contact at high temperature without giving excessive blow‑by when cold