i have a 400 with afr 210 heads drilled with steam holes. i have an electric water pump, stock fan, and radiator. my car runs at about 170 degrees. after my car heats up runs for like 15 or 20 mins i get a wierd knocking sound. it sounds like it is coming out of the water pump. like maybe the water is boiling or something. does anyone know what it causing this and how to get rid of it.

 

anybody have a clue?

 

What type of gas you using? Regular or premium?

 

premium