I use three sealers, and as above, they're used sparingly. For attaching valve cover gaskets, use contact cement, like 3M weatherstrip adhesive ("Gorilla Snot" as the NASCAR guys call it). Put a THIN layer on the gasket and on the valve cover, let it dry to the touch, and press them together. Get it right the first time- - - -it bonds instantly. Leave the cylinder head side as is- - -no glue or sealer of any kind.
Next- - -thin paper gaskets like thermostat housings, water pumps, etc. Use a very thin layer of Permatex Super 300, the brush-on liquid developed in WW II for aviation gasoline sealant. NOT Permatex 3D or 3H- - -it's a different compound. Super 300 is almost black, and never hardens fully.
Last- - -RTV silicone sealer, whatever color trips your trigger. This is actually a "gasket eliminator", made to fill the gap between parts without using a gasket. It's best used at the corners of oil pans and V-8 intake manifolds to prevent leaks where side and end gaskets meet. A little dab is all that's needed! Big squeezed-out gobs of RTV scream "Shade Tree Mechanic!" to everyone who knows better.
One little precaution- - - -NEVER use any kind of sealer on a gasket that's exposed to intake manifold vacuum! Water ports at the end of a manifold, OK, but not the fuel mixture passages!
Jerry
