Im building an ls/vtec and i heard that JDM ITR, and CTR pistons will not fit the stock ls rods without modification. Is this true and will JDM P30 b16a pistons work? and how much compression would i get?

 

P30 pistons will work but due to the type of wrist pins, you have to have a machine shop press them out and push them in for the new pistons. ITR pistons will be lower compression than the P30's and CTR pistons are extremely high compression and will need a really competent tuner to keep them happy on the street.