To find the correct specification, you must consult the official Cummins service manual for the *exact* model number of your N14 engine. This manual will provide the precise measurement for allowable camshaft end-play. Using an incorrect value could lead to engine damage.
Attempting to find this specification anywhere else (like a generic online forum) is highly risky, as it could be inaccurate and lead to improper repairs. The service manual is your only reliable source.