Originally Posted by
njcommodore
The C to A terminal is inside security meant for domestic connections. You're correct that you'll have to clear immigration and customs so once you are through you'll see a bag drop. Then look for the Airtrain to get to Terminal A.
1hr 40 min is enough time at that time of day, though if you're not a US Citizen make a point of walking quickly as the visitor line can quickly grow.
You will have to clear immigration/customs at C, but if you have all boarding passes and your checked bags tagged to the final destination, there is another way that might be faster:
-Drop the checked bags after the customs and then get up and go through security at terminal C. Then go to gate C71C (between gate C71 and the restaurant) and take the shuttle bus to terminal A. You won't have to clear security again and it might save you a few minutes.