I was wondering if CTR pistons would fit into an LS-VTEC setup. I know that its the most common used piston for the setup, but do you have to bore out the block?

 

they fit perfectly fine, but yeild a very high compression ratio. I would recommend the ITR pistons for a daily driver. If a track car or drag car the ctr's would be ok though.

They are the same 81mm bore that ls block has, if you want to bore it out to clean up the cylinders, then just get the oversized ones

 

if you plan on keeping the stock rods, you'll have to shave 1mm off each side of the small end for the ctr pistons to fit.