What will cause valve stem blow-by to the valve section shown in the illustration? Illustration MO-0030

Correct Answer: Option D — Defective rubber seal rings in the valve guides.

Defective rubber seal rings in the valve guides allow sealing failure between the air intake or exhaust space and the valve stem section, resulting in direct blow-by. BrightMariner instructional standards emphasize inspecting elastomer seals during overhauls to prevent pressure loss.