I will explain my story then link to the rest of the debate, if you have already read it then I cannot convince you further.
When I bought my truck it had a 350 crate motor factory built and dealer installed with 14,000 mi on it. About 1000 miles before it shredded the cam I powder coated the pan. There was absolutely no signs of shavings in the bottom of the pan at the time. Reinstalled the pan and dumped in some Mobil 1 like I have run in all my newer vehicles. 1000 miles later I bent a push rod and could not figure out why, until I pulled the motor and dropped the pan. Four of the 16 lobes of the cam were in the form of shavings in the bottom of the pan with wear on the rest of the cam.
The engine had 14,000 miles on it and was plenty broken in. The valves were factory adjusted and stock springs were not applying too much pressure on the cam. The only thing different was the oil I put into the engine.
I am in process of upgrading the engine to all roller components so I will not have to worry about weather or not the zinc was or was not the problem, but I am convinced that the oil was the problem. I am at $3500 on the rebuild and upgrade, it would have been worth it to me to have spent $14 on some race oil and not had to deal with this. It could be that I have a bit of a heavy foot and like to work the engine, maybe standard driving conditions the cams hold up fine with regular off the shelf oil and the harder you drive them the more you need the zinc, because I have also heard guys say they have not had a problem, but I sure did and it is very clear that the only thing that was different in the last 1000 miles was the oil.
Here is my thread on the topic. Some are convinced some are not.
http://67-72chevytrucks.com/vboard/s...d.php?t=489474
Mike