On my 351W, we have replaced the thermostat covere 3 times, and tried a bunch of different gasket sealers and everything. It is constantly leaking antifreeze, mostly from the bottom end of the cover, and now it has started to leak on the top as well, And everyday we check on it, the excess antifreeze is in a huge puddle on the top of the timing chain cover. Is it because we are using a aftermarket intake, its a Edelbrock manifold, or just because we are buying cheap thermostat covers? and does any one know of a good brand, that i can buy, because im getting tired of constantly replacing it, and filling up the overflow tank all the time???