Improper engine break in.

You don't see them professional Pro Stock, Funny Car and Top Fuel boys breakin stuff in for 500 miles. They rebuild um in the pits bust um off to make sure they're right and then put the fire to it. Same in NASCAR.

Once the camshaft is broken in, IMO, it's Katy bar the door. Because if it's gonna break, it's gonna break anyway so you might as well find out.