I really don't want to argue with you Steve, but you're way off the mark. There is no reason whatsoever for a guy driving a flat tappet ANYTHING on the street to use a race
oil and change it every 500 miles.
PERIOD.
I don't know what you or your people are using for filters, what you're using for fuel, or what state of tune these engines are in, but even a flat tappet engine with heavy valve springs should be able to get a lot more than 500 miles between
oil changes. Maybe some people think it's macho to use race
oil and change it every weekend. Still others see it as wastefull and completely unnecessary. Maybe if you're using a door screen for a filter and you're running some ungodly rich AFR, 500 mile changes make sense. But come on, a car running like that would be fouling plugs and tearing up a lot more than just camshafts.
Anyway, I'm not interested in what your friend knows. I'm more interested in what YOU know. If you've got some technical insight that goes beyond "hey, my friend has been building race engines for 16 years, and he said so. . . ," I'd love to hear it!
BK