I put .100 long-2.125 sb chevy intake valves in mine. They also had 5/16 stems. Exh was 1.80 ford 351 cleveland with 11/32 stems. If you are installing new guides you can use any stem size. Smaller means less weight. Engine made over 650 hp at only 10.5 to 1, on a 449/383 engine--4.28 bore x 3.900 stroke. 9.02 at 150mph 1/4 mile-in 2500# car.