you guys are mentioning can break in. but not what your'e breakin in. if you are running a flat tapett cam, you need to make sure that the lifter is spinning in the bore. you can see the push rod rotate if its spinning, so is the lifter.the contact point of the lobe and lifter is the break in. these two parts actually run in together.if you are running a roller,this is no longer an issue. your cam bushings are the exact same as your crankshaft, and you never hear of anyone breakin in a crankshaft, if my pushrods are turning, i run it till it is up to operating temp(thermostat cycles).if adjustable, i check lash, and start driving it just like i intend to drive it.break it in like you will use it.i understand if you think i'm nuts, but if you believe the factory machine work was as good as what you just had done you are too. htem motors were put together in around an hour, maybe got 10 minutes of run time and out the door they went.and more worked than didn't. my two cents, and i hope you don't mind my ranting.