I have some of the remains of a GMC 228 engines that I have been salvaging parts from. Last week fellow 'Bolter TUTS59 needed a set of GMC rods. I took the pistons (which Craig didn't need) off the rods for easier shipping and noticed that one pistons had these marks around 60 degrees of the circumference of the skirt. Is this "knurling"?
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knurling.jpg (205.64 KB, 227 downloads)

Last edited by Bill Hanlon; 07/29/2025 2:56 PM.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12
'52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.