birkhoff Posted January 18, 2017 Share Posted January 18, 2017 . . . Will it consume more oil?... maybe, but probably only a couple extra drops per bazillion miles. Will you notice a difference when you're driving the car?... no way. I've built a couple of oil burners and found it really disappointing, to be honest. Especially after all that effort and money spent. For our engines, your very best insurance against this kind of disappointment is new pistons and a proper machine hone. That will take you from what you have now, which is probably not bad, to very good, in terms of fit and finish. A basement ball hone could make things worse. Yes, some machine shops use ball hones, but they they don't consider them `hones'. They are finishing tools, used to knock the peaks off the honing marks from the machine in order to produce a plateau finish that is popular these days. Supposedly, a plateau finish cuts down the time to seat rings and holds oil better. It can be done on a power hone too. A power hone can remove quite a bit of material, and do it in a controlled way. The ball hone, not so much. Link to comment Share on other sites More sharing options...
StkmltS Posted January 18, 2017 Share Posted January 18, 2017 Don't the rings largely determine how much oil gets by? As long as the hone is good and the ring end gaps are correct it shouldn't burn any more than normal. My DiySB rebuild Got Misfires? Link to comment Share on other sites More sharing options...
birkhoff Posted January 18, 2017 Share Posted January 18, 2017 Well, yes in part. The rings need to conform to the walls to do the job. Rings are pretty stiff in the radial direction, as you know, so there are limits to how much out of round they can accommodate. In the other direction, if you have taper, they have to spring in and out pretty fast to keep in contact with the wall. Consider how many times a second this has to happen as the piston goes up and down. Another point I kind of missed in a previous reply was about taper. I'm not sure the numbers the OP posted reveal all that much about taper. Consider a cylinder with zero taper but now distort one end out of round (Subaru style). Depending on where you measure, you may indicate taper. So some of what we measure as taper may disappear once the bores straighten out when the heads are torqued down. I have no idea how this is done professionally. If it were up to me, I'd take average diameter at top, average diameter at bottom, and call the difference the taper. A machinist being paid for the work might be willing to share some secrets Link to comment Share on other sites More sharing options...
Flatfour02 Posted February 17, 2017 Author Share Posted February 17, 2017 Hey guys! Nearly finished putting the short block together, just a quick question. I'm currently measuring ring gap, wanted to know, when I measure the oil ring, do I measure all three of the pieces that make up the oil ring? Or just the two on the outside? Meaning should I measure the "curly" ring? (Forget technical term ) Link to comment Share on other sites More sharing options...
StkmltS Posted February 17, 2017 Share Posted February 17, 2017 Just the top and bottom rings. The middle one is springy so that its gap is always zero... at least I think that's how the middle ring works. In total you should measure the gap of four rings. Top compression ring Middle compression ring Oil retention ring (top) Oil retention ring (bottom) My DiySB rebuild Got Misfires? Link to comment Share on other sites More sharing options...
Flatfour02 Posted February 17, 2017 Author Share Posted February 17, 2017 Figured as much, once I tried measuring it lol. Well all my middle rings have a gap of .018-.022, and the tops are all about .011-.013. The oil rings I made sure read no less than .01. Should I try to make those a little larger? I know the oil rings can be up to .0179. Should I try to get closer to the larger end? Link to comment Share on other sites More sharing options...
birkhoff Posted February 18, 2017 Share Posted February 18, 2017 It is the top ring that you want to be careful with, shooting for the larger end of the spec for gap. It gets less important as you move down the piston. Larger gaps just means slightly less seal integrity, but too small and it may close up when hot and seize. What did you do for a hone? Link to comment Share on other sites More sharing options...
StkmltS Posted February 24, 2017 Share Posted February 24, 2017 From my rebuild for your reference: (StkmltS's) measured end gap: Top ring - 0.0125" Second ring - 0.0170" Oil rings - 0.0125" FSM specified end gap for '05 LGTs: Top ring - 0.0079" to 0.0098" Second ring - 0.015 to 0.020" Oil rings - 0.0079 to 0.0197" FSM specified end gap for '05 STI's: Top ring - 0.0079" to 0.0098" - 0.039" max limit Second ring - 0.015 to 0.020" - 0.039" max limit Oil rings - 0.0079 to 0.0197" - 0.059" max limit You'll be fine with .011-.013 top gaps. My DiySB rebuild Got Misfires? Link to comment Share on other sites More sharing options...
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