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Hello, I’ve been looking around for oversized pistons for a N12 non turbo engine (2010 R57 rebuild in progress) and can’t seem to find any for the non turbo.
I have found CP Carrillo have some that are for the Cooper S. Does anyone know or has anyone found any for a non turbo N12 engine?
Has anyone changed piston rings after bad oil consumption and been successful reducing the consumption? I just don’t want to be in this deep and make the wrong choice, I don’t want to have to take this engine apart again 😖. Any help appreciated.
Thanks. I was leaning towards CP Carrillo, they’re also better in price. I’m not looking for anything other than restoring stock function and a remedy for the excessive oil consumption.
Did you perform a compression test? What about a leak down? Usually, valve seals are a source of high oil consumption, not piston rings. Not that rings would be out of the question, but would be rare.
I was initially replacing a head gasket from lost compression in cyl 3 and the faint white smoke with a coolant/“sweet” odor, removed head, I didn’t find any valve leaks or warp so I took it to a machine shop for a different opinion, they didn’t find any warpage and the valve seals all checked out good
I was referring to the rubber seals under the valve springs, not the valve seats. If you are rebuilding the head, you should be replacing those anyway.
If you pulled the head to replace the head gasket, inspecting the cylinder bores will tell you if there are any issues. If there are no deep gouges, just hone it out and replace the rings. You shouldn’t automatically need to bore it out and go over size on the pistons.
Yes, they are (the rubber seals) the same seals I was referring to, machine shop didn’t find anything wrong with them or signs of leaks. The oversized piston route was their suggestion, and now that you mention it, when I look at the cylinders I just don’t feel convinced all that is necessary, no gouges or anything. A couple of pistons do look closer to the cylinder wall on one side than the other. I’ll see if I can get a clear photo showing what I mean
Seriously, if you are chasing an oil consumption issue and you are already rebuilding the head, get new valve stem seals.
I am a major proponent of going the extra mile when performing certain tasks, but I don't think oversize pistons are a "while you're in there" item. Crank and rod bearings, sure. New piston rings, definitely. A block over bore and new pistons, not really. But, I'm not you. Is it possible the shop is telling you to replace because he wants more labor dollars?
The head has already been rebuilt, new seals, valves seated etc.
the machine shop has not seen the block, the “oversized piston” route was just something he casually mentioned as a way they’ve cured oil consumption in other vehicles, he doesn’t believe oversized pistons exist for minis so he didn’t suggest I do it. I decided to explore the idea as a worst case scenario and here others opinions. From what I see in the cylinder is, I don’t think all the oversized pistons method is necessary, the cylinder walls look ok, only thing I found odd was cyl 2 and 3 are off in the centering of the piston.
see pic below. Distance between wall and piston on one side (1&3) is much smaller than at 2&4. Does this mean anything?
