Fig 70.1
Two different rubber oil pan seal gaskets were used on 1985 and earlier small-blocks. Original equipment 1955-75 oil pans require a 1/4-inch "THIN" seal. However, current GM service replacement pans for the early 1955-75 applications as well as today's aftermarket pans require the 3/8-inch "THICK" seal. The 1986-and later small-blocks use a one piece oil pan gasket.