Piston ring end gaps should be measured at which location?

Piston ring end gaps should be measured at which location?

• A. At the bottom of ring travel in the cylinder
• B. At the top of ring travel in the cylinder
• C. In the middle of the bore
• D. At the ring seating area

Answer: (A)

End gap is the space between the ends of a piston ring when the ring is seated in the cylinder bore. This clearance must be correct because as the engine runs, the ring expands in circumference with heat, and an end gap that’s too small can cause the ends to butt and scuff the bore, while one that’s too large can hurt compression and oil control. The measurement is taken with the ring in the bore and pushed to the bottom of its travel. This location provides the cold, worst-case clearance the engine will see when the ring is least expanded, and it corresponds to where the ring actually sits during part of the piston’s movement. Measuring here ensures the end gap will remain acceptable under operating temperatures, especially since the gap naturally increases with heat near the top of the bore. Checking at the top or middle wouldn’t give a reliable reflection of the real operating clearance because temperature and bore geometry vary along the bore length.

End gap is the space between the ends of a piston ring when the ring is seated in the cylinder bore. This clearance must be correct because as the engine runs, the ring expands in circumference with heat, and an end gap that’s too small can cause the ends to butt and scuff the bore, while one that’s too large can hurt compression and oil control.

The measurement is taken with the ring in the bore and pushed to the bottom of its travel. This location provides the cold, worst-case clearance the engine will see when the ring is least expanded, and it corresponds to where the ring actually sits during part of the piston’s movement. Measuring here ensures the end gap will remain acceptable under operating temperatures, especially since the gap naturally increases with heat near the top of the bore. Checking at the top or middle wouldn’t give a reliable reflection of the real operating clearance because temperature and bore geometry vary along the bore length.