i picked up a set of oem rings and A0 pistons from a guy on craigslist. the rings were still sealed, but the box for the pistons was marked p73-00(jdm).
i bought them anyways because they were obviously still new and i was getting them pretty cheap. i was just wondering if there is a way to distinguish the oem piston from aftermarkets such as RS and nippons? anybody know if there are any specific markings that i can look for to figure this out?

 

confused., you say a0 pistons and jdm 00. one is usdm the other jdm

as for how you tell. the side coating could be one way

this is a jdm itr piston

 

the box they were in said 00, but the stamp on the pistons itself says A0. so im assuming something was switched here because if they were real jdm pistons they would be stamped 00 as well

 

absolutely would be. the last jdm itr that i blew up with a turbo, on teardown had p73-00 stamped in the piston. you either have usdm pistons or you have a nippon copy that's more of a jdm itr copy.

if i had to venture a wild *** guess i would say that someone bought nippon pistons, then jdm itr pistons, stuck the nippons in the box and scammed you. well...at least hope it's a nippon if it's aftermarket. they are a decent piston. some of the off brands are untested who knows pistons.

buy a cheap gram scale at harbor freight and weigh them. make sure all 4 weigh the same, if they don't grind the heaviest to weigh the same as the lightest. also if you can find the gram weight on a usdm itr piston it will let you know if you have those, or a copy