better listen to builder! synthetics get lots of praise but not long ago people found out that some oils are good for newer engines but not older ones like flat tappett cams. new oils lack the
zinc needed in those high friction areas unlike newer motors which have roller cams and different metals so take
oil seriously I had friends lose a flat tappett cam in less than 1,000 miles to find out they didnt use correct
oil, I use dello 400 diesel
oil myself in my solid lift 390 ford lots of drag racers use it to. good luck hope this sheds some light!