What would be the max temperature allowed for a Core duo quad 2.4 GHZ cpu ?

I built my self a computer this week with a duo core quad 2.4, asus p5n-d mb, 750 w power sup, a geforce 9800gtx, 4 gb ram etc, it runs nicely but there is one thing that worries me, the cpu temp stays on 48-50 C deg. in idle and it goes up to 85-87C deg. when playing battlefield 2 or any other game . My case has one big fan in the front one little in the side and one in the back plus the cpu fan,. what can i do about those temperatures ?