bore oversizing

[sharky559]

ok im going to oversize my bores to .20 but what i wanted to know is do i need oversized pistons or just oversized rings

 

[VETTE_50_TH]

First of all. Why do you need to bore your motor? Is there something wrong with your cylinders right now? Secondly, have you taken it to a machine shop to inspect it? IF you can use the std bore, i would suggest to. Lastly, you cant use oversize rings on a std piston. Doesnt work like that. .020 over pistons need .020 over rings.

 

[my dreamt dsm]

Im not sure but you usually bore out the cylinder walls if one is out of place. And if you over sized one you have to do the other. It's like matting a 2 liter pepsi bottle to a can of pepsi(speaking motor wise). <----- trying to confuse you guys!

 

[sharky559]

na its that right now im trying to put some oem evo 9 pistons and my bores are 85mm and some one told me to go over .20. but if im going over i could still use the oem evo 9 pistons and just get over size rings right

 

[WickedQuikAWD]

na its that right now im trying to put some oem evo 9 pistons and my bores are 85mm and some one told me to go over .20. but if im going over i could still use the oem evo 9 pistons and just get over size rings right

You are talking about 20 thousandths of an inch over bore...aka .020" not .20.
You must use matching rings and pistons. you cannot put over sized rings on a stock sized piston. there will be too much space between the piston and the cylinder wall. The stock bore of an evo is 85 mm by a 88mm stroke. if you have clean bores that are within factory spec then you can use the stock evo pistons with stock sized rings. your cylinders just need to be honed. once again, i repeat, you cannot use over sized rings with a stock sized piston. if you require an over bore, even .010, you must get over sized pistons and over sized rings.

here are stock evo specs...

Powertrain Performance Graph for Mitsubishi EVO IX -06 (206 kW)

 

[sharky559]

sorry bro it was .20 but yea i get it thanx bros for the help

 

[WickedQuikAWD]

sorry bro it was .20 but yea i get it thanx bros for the help

glad to help, but once again, it is .020 not .20

overbore is measured in thousandths of an inch, you are saying that you were told to over bore your engine 200 thousandths, instead of 20 thousandths. there is no way you can overbore an engine .20"... there is not enough block to do so. largest overbore ive heard of in these engines is .040" or 40 thousandths. Just trying to help you get your measurements straight. Best of luck with the build.