Inside the SOHC ZC Engine I pulled the head to replace the head gasket today (5/3/2003). This is what the SOHC ZC engine looks like on the inside. The first few pictures are for everyone out there who wonders what kind of pistons are in the SOHC ZC. I also had to prove it to myself. You can clearly see the "PM6" stamp on the top of the piston, as well as the "ZC" stamp on the block. The PM6 pistons are the exact same as the units found in the USDM 88-91 Si (D16A6) and yield a static compression ratio of 9.1:1 in this engine. Images on this page are approximately 90kB (600x450) each, and are clickable for more detailed 265kB - 320kB images (1280x960) in new windows.