many, many years ago, i built a 440 to race in my 68 GTX. it had a HUGE bottom end grunt, and revved like a pro stocker, but at 3500, it fell on it's face ! i had advanced the cam 4*, but had mixed up the marks. upon tear down, i found the valves had lightly kissed the pistons. pistons were ok, but had the heads re-done because of a couple of valves. re-indexed the cam and crank gears, this time DEGREEING in the cam like i should have done in the first place.
didn't rev like a pro stocker any more, but ran real good. as was mentioned above, it is very possible the timing chain set is marked wrong, or installed incorrectly. just my experiance, your mileage may vary.