adamdaviddoyle,
If the noise only happens at startup I'd look into adjusting the valves. However, I've been able to eliminate that noise by using a different oil. You mentioned the viscosity you normally use but not the brand. I've found that an oil with a higher ppm of molybdenum will quiet things down...something like Pennzoil High Mileage will do the trick. Or, if you want to spend the money, RedLine.
Bogatyr