We have the cnc ported stealth heads and they are great, with 1.5 rockers a little bit of grinding was required for the pushrods and i would get new springs, retainers, and locks, the stock springs broke with a 528 mp solid cam, now we have 1.6 440 source rockers and everything is working great, they are a great product and the giys at 440 source are very helpful, when the one spring broke it bent a valve and they sent me a new spring valve retainer and locks.