dmend Posted October 22, 2020 Share Posted October 22, 2020 I'm doing my first ring replacement and both Haynes and The EndWrench Subaru Overhaul document say "Piston and bearing dimension information is stamped on a machined surface where the crankcase halves meet." My EJ22 doesn't have that. The Haynes book lists A, B, C spec variations but no explanations for them. Can anyone explain how to use these specs? Thanks, dmend Link to comment Share on other sites More sharing options...
doublechaz Posted October 23, 2020 Share Posted October 23, 2020 It's in the FSM. It's probably a little too technical for a generic service book like a Haynes. The relevant pages are in this link. http://mynet.whitehat-inc.com/subaru/engine-spec.pdf Link to comment Share on other sites More sharing options...
Osei Posted October 24, 2020 Share Posted October 24, 2020 Once all the top mount stuff is removed, you'll see the marks. They show the piston sizes. Generally you will only find an A or B. But it doesn't matter for what you are doing. Put an A piston in an A bore etc. If you had to get another piston. Just put them back in the bore they came out of and that will eliminate any issues. Remember to put the dot on the piston facing the front. O. Link to comment Share on other sites More sharing options...
dmend Posted October 25, 2020 Author Share Posted October 25, 2020 Thanks for the link. Got the FMS and with further google searches now understand the different sizes. Could this be an aftermarket block since it doesn't have the stampings on it (see picture above). I've got Cyl #1/B-piston, #2/A, #3/A, #4/B. Need to replace #3 piston due to slap that damaged the skirt. Only place I can find a single piston is Subaru parts and they only I.D. pistons as left or right, no A or B choices. Just thinking through this....isn't the point of the A-B sizes to best fill the cylinder to match compression and minimize vibrations by pairing the A and B properly. Maybe not enough of the pistons sold to warrant manufacturing different sizes anymore. Thanks, Dmend Link to comment Share on other sites More sharing options...
doublechaz Posted October 25, 2020 Share Posted October 25, 2020 Piston and bore sizes have to match spec to avoid slap. Perhaps they only sell the larger size and expect you to bore/hone to match. Rebuilding an engine by hand is different from banging together hundreds of them per day on the assembly line. Link to comment Share on other sites More sharing options...
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