Took the valve covers off of my 396 for the first time today to attempt a valve adjustment. To my surprise I noticed some rather large holes next to half of the push rods (all on the intake side). The holes were all on the (lookers) left of the #1, #5, #4, and #8 intake valves.
the motor has been running, albeit rough, so I am not sure when/how these happened.
How are these caused? Are they catastrophic? Is this considered normal? What should my course of action be at this point?

!!!
Thanks!
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1968 Chevy C-20 w/ 396

1997 HD Sportster 1200 street tracker
1994 Chevy 1500 Silverado