oem gsr pistons on oem ls rods is machining required to get them to fit? i thought all b series pistons would fit.... but i do remember now that some dont... I know the b16a pistons fit without machining the small end.

 

Just a suggestion, but you should look into some other pistons, gsr pistons arent going to raise your compression much, which im assuming is what your trying to do. Look into some p30's, pr3's or p73's. RS machine has pr3 replicas for $150 with rings on ebay if your on a budget. I know p30's fit without machining and p73's DO need machining, dont know about pr3's.

 

GSR and ITR pistons will need machining, all B16 pistons will clear LS rods.

 

You need to machine 1mm off the small end in order to fit the GSR/ITR pistons.