Probably enough. Even though it's a big airport, it's efficient. If you are flying Turkish Air, there are 5 flights a day (per their website), so the worst case is that you'll be stuck in the airport for several hours till the next flight out. No customs or immigration in IST for connecting flights, but there will be a security check. If you have checked luggage, I strongly encourage you to pack what you need for the first 48 hours in your carry-on, with that short a connection, it's possible that your luggage will be delayed.
If you are flying Turkish, have you considered flying via SFO? They fly non-stop SFO-IST. It's a long flight, but eliminates the JFK connection - which can be difficult I'm told. Also consider your return flights. Will you have to go through immigration and customs in New York? That's another pain.