I’m tearing down a 235 engine and I’ve observed the following:
Why do the piston heads have a “dimple” in the center?

Why are there two holes in the head cooling jacket and in the corresponding matching block surface there none? The reference area are between cylinder 1 & 2, and cylinders 5 & 6

See attached photos.
Attachments
IMG_9927.jpeg (200.18 KB, 143 downloads)
IMG_9926.jpeg (335.29 KB, 143 downloads)

Last edited by TexasA&M48Truck; 06/13/2026 7:54 PM. Reason: Added ref affect areas