I'm helping a friend put a new cam in his 383. Just an old DC .509 that has been on the shelf for 30 years. He last changed his oil 18 months ago with 10/30 VR1 and 1/2 bottle of GM EOS. He has less than 100 miles on the oil change. He insists that it will be fine to leave that oil in for the cam break in and change it out after 30 minutes. I am not totally comfortable with this, but I don't really see a reason not to. Any opinions on this?