If you're convinced the valves are properly adjusted, removing oil pan may be your best option to find a loose nut. That's not a terrible thing, just kinda messy.
Matthew 6:33
1952 Chevy 1/2-ton 3100 Late '55 235/SM420/torque tube 3.55 Dalton Highway survivor (using original 216) www.truckwithaheart.com
