jonathan909 Posted January 3, 2019 Author Share Posted January 3, 2019 New question: My exhaust valves (and for some reason, it's a lot worse on one head than the other) have a thick white deposit on their faces that's really hard - the wire wheel barely touched it, and I had to take most of it off using one of those little sintered Dremel burrs. What is it, and why is it there? Link to comment Share on other sites More sharing options...
idosubaru Posted January 3, 2019 Share Posted January 3, 2019 That’s annoying. Wait - do you have to remove the valve to pull the shims? It’s been a long time since I pulled an EJ25D apart, most rusted away around here so I avoid them now. On EZs it’s super easy. Pull shim, grind, recheck, grind, etc. No need to monkey with valves and springs and stuff. It’s super easy with the engine out of the car anyway. Link to comment Share on other sites More sharing options...
idosubaru Posted January 3, 2019 Share Posted January 3, 2019 I’ve seen the white before. Don’t know what it is. Link to comment Share on other sites More sharing options...
jonathan909 Posted January 3, 2019 Author Share Posted January 3, 2019 (edited) 55 minutes ago, idosubaru said: That’s annoying. Wait - do you have to remove the valve to pull the shims? It’s been a long time since I pulled an EJ25D apart, most rusted away around here so I avoid them now. On EZs it’s super easy. Pull shim, grind, recheck, grind, etc. No need to monkey with valves and springs and stuff. It’s super easy with the engine out of the car anyway. No - the valves don't have to come out to pull the shims, but I removed/reinstalled the one I had to grind the stem on. I suppose one could grind it in situ, but I don't think I'd try that myself (for the obvious reasons). But lacking Subaru's (expensive) fancy-shmancy tool, the cam has to come out for each shim change - or at least be loosened off to get the clearance to slide the shim out. Shim grinding strikes me as counterintuitive. Much more material to be removed than just grinding the valve stem, and unless you've got precision machine tools, impossible to grind true. Edited January 3, 2019 by jonathan909 Link to comment Share on other sites More sharing options...
jonathan909 Posted January 3, 2019 Author Share Posted January 3, 2019 55 minutes ago, idosubaru said: I’ve seen the white before. Don’t know what it is. Stands to reason that it'd be carbon, but maybe in some weird annealed state. Not being a carbon chemist, I really can't speculate further, but I remain curious. Link to comment Share on other sites More sharing options...
GeneralDisorder Posted January 3, 2019 Share Posted January 3, 2019 Yes unless you have a surface grinder with a magnetic chuck, you're not going to grind the shim truly flat. Which could cause camshaft lobe wear issues. I would not attempt this. I have tried lapping them and you might as well be trying to lap diamond. They are quite hard and silicon carbide made no noticeable change to the thickness after several minutes of work. You could soft-jaw it up to the lathe or even super-glue it to a mandrel and use carbide tooling to thin them down also. But that's way beyond the scope of what is sane for most people. I certainly wouldn't bother. Grinding the stem in a fixture or even by hand while turning it against the grinding wheel is sufficient and quick if you are careful. GD 1 Link to comment Share on other sites More sharing options...
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