I have an old aluminum intake for a BBC that is pitted around the water jackets. I filled the pits with JB Weld and am getting ready to put it on the engine. But I got to wondering if it would be better to machine off the mating faces a little. Ever had a manifold machined on the mating faces? How much can I go without trouble? Or should I use thick gaskets, plenty of sealer, and install it like it is?