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420A NPR Piston rings

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powellds2

15+ Year Contributor
221
6
Dec 3, 2007
Baker City, Oregon
So I'm assembling my new motor and I was just gapping my rings... First and second are good to go, then I get to the oil rings.... WTF? They are all too big. Like, I would have to cut the oil control ring just to get it in the block to check the gap.... I'm talking like, 1/8 inch excess on the control ring that needs to be cut off. As for the upper and lower control rings, they have literally no gap at all.... Did the oil rings from another set get mixed up with mine? Anyone else have this experience? The two top rings were actually all within spec right out of the box. The oil rings just have me wondering what happened. This is the second set of NPR rings I've rebuilt a motor with and they were not like this.
 
I'm actually referring to the oil expander ring (my bad). As far as I can remember from my other builds, I've never had an expander ring this large... I can butt the ends up to each other and compress them on the piston and install them, but is that okay? I've just never had this much excess on an expander ring.
 
Something sounds fishy. Generally you should have a larger gap in the upper and lower control rings. Though the expander ring normally can seem to be too big, I'd be suspicious because of the "no gap" oil rings.

I haven't used NPR for these engines so my suggestion would be to fall back to the paperwork. If that doesn't help you, then I would contact NPR (for, if nothing else, peace of mind)
 
Ended up scrapping the rings. I can't remember where I ordered them from and didn't want to deal with the headache. Got a different set from another rebuild kit and these fit perfectly. So I either ended up with some bogus expander rings, or someone mixed up a set. Either way, if any of you use NPR rings for a stock rebuild, or any rings for that matter, always check them first! :)
 
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