440 problems ,new motor

I checked the bolt it was a fresh break through . nothing showing previous damage.it was a original bolt from the old cam. I was also told that the stock cam bolt can be bottomed out on some aftermarket cams. Then your torque is just twisting the bolt.
the plan sounds like a tear down, pull the heads look for damaged valves , valves hitting the pistons. see if the cam turns freely , pull it check for wear. I have the engine on my run stand so the process is easier, hope its not expensive . I will be pulling it apart tonight