Maggie13 Posted January 31, 2023 Share Posted January 31, 2023 I'm in the middle of rebuilding my engine. I think my piston ring gap is too tight. What is the minimum gap? I can't find it in my manual. Do I just clamp the rings in the vice? Will it not score them? And then try and file at the same angle. Quote Link to comment Share on other sites More sharing options...
JohnD Posted January 31, 2023 Share Posted January 31, 2023 A good Rule of Thumb is to have four thou per inch of diameter. Measured IN the bore, placed and levelled half an inch below the rim with a naked piston. Yes, hold the ring in the vice, with as little showing as possible to avoid breakage. Padded vice jaws are nice, but not essential! Use a sharp (new) fine file and go slowly. Good luck! John 1 Quote Link to comment Share on other sites More sharing options...
Maggie13 Posted January 31, 2023 Author Share Posted January 31, 2023 I need to check again but I think I have a tight 10 thou. The bores are honed as well if that matters. Will the gap not get wider as they bed in? Quote Link to comment Share on other sites More sharing options...
glang Posted January 31, 2023 Share Posted January 31, 2023 Think youre right the gap will increase slightly with ring wear but must be big enough intially so that expansion due to heating doesnt make them too tight and at risk of breaking! Quote Link to comment Share on other sites More sharing options...
PeteStupps Posted January 31, 2023 Share Posted January 31, 2023 Spitfire isn't it? According to my 'glovebox' workshop manual the gap should be 12 to 22 thou. So 10 is indeed a bit too tight. Personally I would gap them after the bores are honed. Not sure if it makes a measurable difference though. Pete Quote Link to comment Share on other sites More sharing options...
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