Question 157Motor Plants - 1st Asst/Chief

The correct answer is C) Length of the piston skirt. In a loop or cross scavenged engine, the length of the piston skirt prevents the air under the pistons from being pumped back through the scavenge ports during the piston power stroke. The piston skirt acts as a barrier, sealing off the scavenge ports and preventing the reverse flow of air, which is essential for the proper scavenging of the cylinder. The other options are incorrect because: A) Positive pressure from the blower is responsible for providing the scavenging air, not preventing the reverse flow; B) Masked intake ports are not relevant to the scavenging process; and D) Lower liner seals do not directly prevent the air from being pumped back through the scavenge ports.