If a big block Chevy oil pan is not properly sealed before it is installed, you will have constant leakage issues, especially at higher rpm. The common place an oil pan leaks, even after installation of a new gasket, is just under the timing chain cover. Often, the bottom of the timing cover leaks, and it looks like the oil pan is leaking. If oil is left to leak without being checked, it could get too low for the oil pump pick-up tube to grab it, and this could cause extensive engine damage.
Squeeze a 1-mm bead of RTV silicone on the oil pan's gasket mounting surface, on the sides of the oil pan, but do not cover the bolt holes. Allow the RTV to set for two minutes. Fit the gasket onto the oil pan, making sure the bolt holes in the gasket line up with the bolt holes in the pan. Wipe off any excess RTV that squeezes onto the inside of the oil pan.
Squeeze a 3-mm bead onto the front and rear of the oil pan where the crankshaft rides. Allow this to set until it is dry to the touch -- about 10 to 15 minutes, depending on the amount of humidity in the air. Do not use the gaskets that come with the oil pan set, as they tend to leak.
Coat the top of the gasket with a thin layer of RTV -- just enough to help it stick to the engine block. Mount the oil pan to the engine. Insert the oil pan bolts and tighten them by hand as far as you can. Tighten the bolts firmly, but take care not to overtighten them, as doing so will squeeze the gasket and the RTV out and cause the gasket to leak.
