yes, its normal to get warm, especially moving 50amps. Out of curiosity, what kind of relay are you running?
If im not mistaken there are 2 speeds for that fan, and the low draws about 50 amps and high draws 75-80? ( i remember someone posting such info after using the search for this topic)
If I were you, id be using a relay like this
http://www.034motorsport.com/product...roducts_id=405