Doug, one thing about epoxy in the ports is that the epoxy adheres better to itself than to the aluminum or cast iron. So, make some mechanical points where the epoxy can't get out when you do this. For example, when doing the ports on a head, cut a thumbprint or groove out of the manifold mating surface into the port, and then when you put the epoxy into the port, fill in the groove also. File it flush with the mating surface of the head, and then when the manifold is bolted into position that part of the epoxy is sandwiched between the head and the manifold, and can't come out. So, if the epoxy starts to come loose from the aluminum or cast iron, you will have a mechanical hold to keep it in place. Blair P gave me that particular bit of wisdom, and I think it makes a whole bunch of sense...