h23 are plumbed for vtec but with mine i opted to run a external 7/8'' oil line directly to the head so i wouldnt have to mess with block. as far as the redline goes in h23/h22 motors and LSvtec motors of course the blocks cant redline as high as there vtec heads allow them but that can be fixed with rods,pistons, and balanced and blueprint job. then they are capable of turning as many rpms as the rods and pistons are rated for. The payoff is the incrediable tourqe from the motors with the addition of vtec.