We havnt installed LS pistons in a VTEC motor, but I was under the assumption that the valve relief on the LS pistons isnt enough to clear the valves.. I will look into this more, but im almost positive there will be clearence issues with the valves... Thus the reason you dont use the LS pistons in a LS/VTEC unless you clay the motor to be 100% sure.(I could be wrong, but I dont think sooo...)