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so im currently building a b20v with ycp 84.5mm piston and npr piston rings...when i measure the all the piston ring (1st,2nd,and oil ring) the clearance i got on is .017 would this clarence be good enough or would i need to gap it alitte more....the second thing i would like to know is are there any calultion for piston rings that i would need to do?
2nd ring gap should always be a little bigger than top ring gap.
and yes there is a calculation for determining proper ring gaps for top and 2nd ring, and it depends on your power goal and/or general setup. ie: stockish, high comp n/a, nitrous, turbo/supercharged, etc.
I will be running .014" for the top ring and .017"-.019" for the 2nd rings. 85mm bore NA street engine.
man that seems a bit tight for the top ring like maybe a .004 multiplier......
the ring gap doesnt necessarily depend on piston material thats more for the piston to wall tolerance.
to calculate the ring gap you multiply the cylinder bore (in inches not mm) by a certain number. maybe something around .005 for all motor and like .006 for boost, unless you are running crazy power. the second ring is often .003-.004 larger than the top ring. the oil rails just need to be at least .015 inches. check the ring gap with the ring about or a little less than halfway down the bore and make sure it is square in the cylinder. i usually use a piston to push it down and stop when the piston just about hits the bottom of the skirt on the block deck. dont forget to deburr or smooth off the end of the filed ring to remove any sharp edges. just a quick hit with some real fine grit 600-800 sandpaper will do the trick. remember to only file one side of the ring and make sure its parallel to the other end of the ring when compressed.
now, since your rings all measured out at .017, i would bring the gap on the 2nd ring up to .020 and run it. properly broken in i really doubt you will have any issues with those numbers. the piston to wall should be between .0015 and .002".
^^ would this calulation work my my kind of piston.. my piston are cast like oem
Piston material isn't going to matter with your ring gap . . . the clearance built into the ring groove means the rings should be free-floating all the time.
The values are set on the heat primarily which is what causes the ring material to grow/stretch.
man that seems a bit tight for the top ring like maybe a .004 multiplier.......
It would be a little tight using .004 for the top ring multiplier, but using the .0045" multiplier, it comes out pretty close. 85mm bore (3.3464" x .0045" = .0150") so I might be about .001" tight. Ive contemplated on opening it up a couple more thousandths, but the last I really thought about it I felt .014" would be ok. Perhaps I should open it up a little to be safer...
After the rings and cylinders break in together, I wonder if there is any measureable change in ring gap?
I don't know how much wear occurs during break-in of a properly set up motor, but ring gap will open by 3.14 times the difference in bore wear. meaning if the cyls wear 0.00025, thats 0.0005 bore increase, which equates to ring gap opening 0.00157". and if the rings wear the same amount, the gaps open the same amount. for a total of 0.00314" (0.003") increase in ring gap.
I don't know how much wear occurs during break-in of a properly set up motor, but ring gap will open by 3.14 times the difference in bore wear. meaning if the cyls wear 0.00025, thats 0.0005 bore increase, which equates to ring gap opening 0.00157". and if the rings wear the same amount, the gaps open the same amount. for a total of 0.00314" (0.003") increase in ring gap.
Yia Yang, see the picture below for reference, it's from JE pistons. It's a very simple calculation based on your bore diameter. Each application is bore and use specific depending on aspiration etc. If you are really going to push the limits of your engine, i'd recommend going an additional .0005"*bore diameter for the top and second rings depending on the application that applies to your build. The reason you want the second ring end gap larger than the first is to keep the top ring seated. That helps keep blow-by and oil consumption at a minimum. Oil rings generally come with the correct gap, sounds like yours are fine.
04-05-2016, 06:43 AM
ring gap..Need help!!!!
