MarceraB16 Posted February 19, 2022 Share Posted February 19, 2022 I wanted to get some better pistons for my Legacy but I'm not sure what the stock piston size is and I'm getting different sizes online. And the ones I'm looking at to buy are 99.5mm or 99.75mm. Which of those sizes would match the stock piston size? Link to comment Share on other sites More sharing options...
Pleides Posted February 19, 2022 Share Posted February 19, 2022 Is there any reason you aren’t just buying an entire new short block? Link to comment Share on other sites More sharing options...
Haze Posted February 19, 2022 Share Posted February 19, 2022 Stock bore is nominally 99.5 mm but Subaru actually used two slightly different sized pistons and your engine likely has a mix of them. I have two EJ255 blocks that each have 3 "A" bores and one "B" bore. IIRC, the "A" piston is .01 mm larger than the "B" piston. The blocks are stamped on top along the center line to identify which piston to use in each cylinder. Link to comment Share on other sites More sharing options...
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