Which statement about piston rings and cylinder finishes is true?

Which statement about piston rings and cylinder finishes is true?

• A. Cast iron rings may be used in chrome-plated cylinders.
• B. Chrome-plated rings may be used in plain steel cylinders.
• C. Both are true.
• D. Neither is true.

Answer: (C)

Piston-ring material and bore finish must work together to create a good seal and minimize wear. A chrome-plated bore is very hard and smooth, which lets cast iron rings seal well after they’re seated during break-in; the bore’s hardness helps resist wear while the softer cast iron rings conform to any small imperfections to form a good seal. On the other hand, chrome-plated rings have a hard, wear-resistant face that can perform well in a plain steel bore, where the surface isn’t as hard as chrome but remains smooth enough for the rings to seal when properly lubricated. With proper lubrication, correct gaps, and correct break-in, both pairings are used in practice, so the statement that both are true is consistent with engine maintenance principles.

Piston-ring material and bore finish must work together to create a good seal and minimize wear. A chrome-plated bore is very hard and smooth, which lets cast iron rings seal well after they’re seated during break-in; the bore’s hardness helps resist wear while the softer cast iron rings conform to any small imperfections to form a good seal. On the other hand, chrome-plated rings have a hard, wear-resistant face that can perform well in a plain steel bore, where the surface isn’t as hard as chrome but remains smooth enough for the rings to seal when properly lubricated. With proper lubrication, correct gaps, and correct break-in, both pairings are used in practice, so the statement that both are true is consistent with engine maintenance principles.