I had that happen to me with my 493. The cam would get to tight and had to be tapped in. I did not like it and removed the cam bearings one at a time as I had installed them myself. When I found the one causing the problem I looked close and found a piece of eng casting had rolled over and got behind the bearing between the bearing backside and the block which raised the bearing surface just enough at that point to make the cam bind up. I could see the scratch on the back of the cam bearing also when I looked real close. I cleaned the casting off and honed the cam hole and reinstalled all the cam bearings and all was fine. Good luck with it as it can be a pain when you get these problems we dont need. Ron