XR or EX cam, whats the difference?

What is the difference between an XR 400 dirtbike cam and a 400EX cam. What are the performance gains that the XR cam offers?

[RAPTORAZ]

The XR gives up just a touch of bottom end power but has a lot more mid to top power.

[fourplay]

I just put the XR400 cam in my bike today. I have a t4 slip on, k&n filter, dyno jet kit, sparks advance key, 14 tooth front sprocket, and a stock piston. My buddy has the same set up except for a wiesco 10 to 1 piston - 40 over. He does NOT have an XR400 cam.

Before I put the cam in, we ran the bikes several times with the same results (he was always a bike length ahead of me) We switched bikes, with the same results. He was still ahead. We figured it was weight difference, since I am about 35 lbs heavier than he is.

After installing the xr400 cam, we ran the bikes again. My bike is now about two bike-lengths ahead of his. We switched bikes, to see if rider played a role. My bike was still two bike lengths faster, regardless of which one of us rode it. Obviously, the cam makes a difference! It seems to rev out quick in mid-range. I did not notice any loss of bottom end.

Terry at Marcum's said that there would also be a big difference with a JE 10/8 to 1 piston. That's next on the list! Hope this give you some idea!
......fourplay