. . . is produced when using a piston with a part number of "10437"? I see no other markings on this piston. It was removed from a Lycoming, O-360 (parallel valve) cylinder. Please assume "standard" length connecting rods and crank shaft throws!
The current Lyc part number is 75089 for 8,5 to 1. nearly all parallel valve 360's use this piston. There are a few that are derated to 7.2 to 1, rated at 168 horsepower and approved for 80 octane. I find no reference for the pn you posted.
