Cam break-in is the FIRST thing you do, immediately after the first startup, as soon as you see oil pressure. The first few minutes of running are critical, due to the scuffing action of the cam lobes against the bottoms of the lifters. The high RPM is needed to assure that lots of oil gets thrown off the crankshaft and rods to flood the cam with oil.
I've seen race cams with high valve spring tension ruined by less than a minute of idling on startup. We generally assemble the heads on our round track engines with street-type valve springs, do a cam run-in, then remove the heads and install the race springs. The cost of a couple of head gaskets and a few hours of labor is insignificant, compared to the possibility of ruining a $1,000.00 cam and lifters on a $15,000.00 engine.
Maybe you got lucky, but don't run it again until you can do the cam breakin right.
Jerry
