I have a stroked 351 putting out over 500 horsepower and Canton Mavhine works who built the motor used Valvoline 20-50 racing
oil in it fo the dyno runs and also recommended that for me. I have used it for over 5 years now and have never had a problem. I also have used it in my big block Torino Cobra since 1969 and it has worked great.
Ron61