If you are a 1969 to 1991 V8 you should have some extras of these on hand. They are inexpensive and should be replaced anytime you remove your valve covers. The gaskets will keep a good seal longer than the bolt washers. These will fit all M116 3.5, 3.8, and 4.2-liter V8 engines from 1969 to 1991 350, 380, and 420 models. All M117 4.5, 5.0, and 5.6-liter V8 engines from 1971 to 1991 450, 500, and 560 models. As seen on Cherry. CLICK HERE to watch the full video series on Kent’s R107 rolling restoration.
If you don't want leaks replace these every time you remove the valve covers
M116 and M117 Valve Cover Bolt Copper Sealing Washers Set of 8