You should NOT be using the clear silicone - go to any auto parts store and get the stuff made for high temperatures. They have "form a gasket" and "gasket sealer" - you want the latter (smaller tube).
Did you put sealant on the H20 pump bolt threads? Since they go right into the water jacket, you need to think about leaks there too. I put a dab of red form-a-gasket on there, and no leaks yet.
(But I must qualify that - I haven't actually filled the engine with water yet...
)
-Boyo
