I have a cheesecake recipe that I have used for years, It is as close to perfect as I need it to be...except, sometimes it cracks (maybe 1 of 5). I have never used a water bath and I don't want to start. I was thinking if I lower the temperature from 350 to 325, it might stop occasional cracking. If I bake for 41 minutes at 350, how much time should I add if I bake at 325? It has also been suggested that I add a tablespoon of cornstarch to the recipe...any thoughts on cornstarch. Thanks
The best way to prevent cracking is to use a water bath. It will give you consistently perfect results every time. The payoff is worth the extra effort.
A cheesecake is a baked custard and controlling the temperature is an important component in uniform cooking. Especially in a thick cheesecake, it is hard to finish cooking the center without the perimeter areas overcooking unless you use a water bath.
Having said that, the second best way to avoid cracking is to use an instant read thermometer to test the internal temperature at the center of the cheesecake. Most sources are pretty clear that if the internal temperature rises above 160 °F, the cheesecake will crack so you should either turn the oven off or remove the cheesecake from the oven—depending on your recipe—when the cheesecake registers just over 150 °F.
Unfortunately, although the temperature of the cheesecake at its center should be a foolproof way of preventing a side-to-side crack along the top of the cheesecake, without a water bath it is still possible that there might be cracks along the outer regions of top of the cheesecake if those areas overcook from being unprotected.
Lowering the temperature might give you more control over the consistency of cooking, but it won't eradicate the risk of having the exterior of the cheesecake cook-through before the interior is sufficiently set.
Ultimately, to get back to your specific question, there is no reliable time-for-temperature adjustment that can be recommended. You will enjoy much more reliable results using internal temperature to tell when your cheesecake needs to stop baking. And I can assure you that using a water bath would revolutionize your cheesecakes.