whelp, Im ready for the flaming but here's my situation. I was at 84.5mm and had some light scoring on the cyl walls. it cleaned up nicely, but it made the bore a bit bigger currently measuring 3.3338-3.3340". some skirt coating from swaintech and my ptw is good to go. the end gap on 84.5mm rings was too big out of the box so i bought some 85mm rings and filed them down. the top and oil scraper ring are gapped and good to go but the oil control rings im not sure about. ive got the 2 skinny rails gapped (i know your not supposed to file them but i had to the ends overlapped and wouldnt fit). what about the middle corrugated looking ring? it fits in the bore but with no gap at all. does it need to be open a bit in case of expansion?

 

No, the oil expansion ring is fine. As long as your top and bottom oil control ring is gapped properly (minimum gap) you are good to go.

 

oil rings just have a minimum gap. as long as your end gap is larger than the minimum stated you're good

the middle piece just has to be butted up and snapped under the two rails (if that's how yours is made at least. my je rings were like that)

 

you may want to consider using the 84.5 oil control rings vs the 85. The corrugated rings like to snap when egg shaped. Even if you trim it, the 20 over expander will want to distort. You may be risking breaking tangs and re doing it later.

The top rings are fine to file down... The oil control rings not so much. I have made this mistake before. The good part is you are right in the middle with your bore. I would err on the side of caution and stick with the 84.5 for the expander. just my two cents.

 

ah **** I returned the 84.5's when I realized they didnt fit. I gotta check my parts stash to see if I have another set somewhere. next question then is it ok to have a gap with the 2 ends of the corrugated ring? this is my boost motor and will likely see over 500 whp

 

:/ not really. You would ideally want the ends to butt in a V with the v pointing down. That's how I do it.

I take the piston and set it in the bore. Then place the expander into the bore. Filing it until it butts tight to each other. I also do the expanded first because they take longer. Some folks take it to a whole nother level and incorporate drag into the process but I've always had good luck with a nice clean butt.

Expanded take me the longest to get right. If they are binding or have any stress they will break.

you will probably be okay with the larger expander just be sure it compresses good, spins freely and so on. For me it's kinda risky. If it doesn't want to sit square on the piston when it is filed I would try the smaller ones.

 

good advice ill do that next time im in the garage