Late 60s early 70s SBC are known to have bad cams that wore excessively. I have a 68 327 that had 100k + miles on it when I got it. When I went to adjust the valves, I noticed that some were barely moving 1/4 inch if that. Ran a lot better with a new cam. I also have a 72 350, that I picked up used. Having had problems with the 327 I checked the 350. The 350 cam was not as bad as the 327, but showed wear of 10-25% on all lobes. My experience.
Larry
