Depending on your intake, the rear water ports in the head need to be vented (burped) to make sure there isn't any air trapped. If the intake has a rear water crossover, great, if not, drill and tap for 1/8" pipe and get a part of AN to 1/8" pipe fittings and a pair of AN caps. When filling the cooling system, crack the AN caps open and let the system burp the air out.