Have a 289, 10 1/2to 1 pistons, stock heads 60k overbore, roller cam and lifters. Single plane with a 600 holly and stock manifolds and exhaust. The engine began to use
oil, when I hooked up the stock exhaust and mufflers. Have installed a weaker PCV and have an open
oil breather. Consumption, seems less, but still there. On the plus side, it runs much better with the exhaust's back pressure. Maybe a 3.8 turbo PCV is all I can come up with. Vacume is low, due to the cam. Any ideas????