I'm wanting to bore a JDM b16a block .040" and use oversized pr4 pistons for boost. I was wanting to know if this is a safe bore on stock sleeves? I'm going to be using a block guard also but if questioning the 82mm sleeve. Thanks

 

I think you will find that pr4's are a max of +.010" (.25mm).The stock pistons will most likely fail before the sleeves will crack.