I have a good friend-Ford guy. He's got a real nice 66 Galaxie with a 390. His brother rebuilt the engine a lot of years ago-I thought he knew what he was doing. Anyhow the builder brother told him just to use regular oil in it. Last year at 18,000 miles it was running bad and lifters clattering. Cam and lifters bad. He pulls engine out, cleans it up, I don't know how good. He installed a new Comp Cam and lifters and drove the car around a little bit. Started clattering again at about 300 miles. I don't know his break-in procedure. So I don't know.