Another thing- especially on a 409 with an aluminum intake--my first 409 had an oil leak I had trouble finding, you drove it nice, no leak, you got on it, it would leak. I put valve cover gaskets on it several time, intake gaskets, a pan and rear main seal set, same thing. Some time later, I broke a valve in it, cracked a cylinder wall, built some heads, had it sleeved, did a nice stock rebuild. Reinstalled the engine, same thing. Then, I got lucky. The top of the intake behind the rear carb had wet clean oil on it, which would run down around the rear of the motor just like it did the first time around. I had a firewall mounted coil on that car, and never put the OE coil mounting bolts back into the intake. One bolthole was blind-it didn't go through the intake. The other one did. It went right into the lifter valley, allowing hot oil off the camshaft to spray right out that hole. Make sure all bolt holes in the intake are equipped with a short fastener or some kind of plug.