Improper engine break in.

My main concern is not changing the oil right after the cam was broken in. IMO $20 for a good filter and 5 qts. of oil is real cheap insurance. As far as romping on it right after it's assembled it really depends on how tight the bearings and pistons were. If it's just a re-ring, no new pistons and crank it should be loose enough that going straight out and letting it rip won't hurt any more than it would 500 miles down the road. Brand new cars when assembled needed a little time to loosen up because the engines were built with real tight tolerance's so they'd last 100,000 plus miles. That's why they recommend a break in period