Other than a manufacturing defect in the timing set or a stack up of tolerances on the block, about the only way to get slack in a new timing set/chain is if the block main bores were bored and honed. This moves the cam and crank closer together. If that has been done, there are undersized timing sets (0.005" and 0.010" undersize are commonly available) to compensate for the line boring. One example:
Cloyes p/n 9-3100-10