Paul,
I recommend you stop using Valvoline VR1. It doesn't have sufficient ZDDP. It's probably why you lost you cam eventually. You need to switch to a proper performance
oil. Joe Gibbs Driven hot rod
oil is the only way to go. Take a look at the Anglo American
Oil website and all will be explained. They are the UK distributer for Joe Gibbs & Sunoco racing fuels.