while the valves are the same size seat on at least the older medium frame H, that is an intake valve and cannot be used on the exhaust, since it is steel. You can go the other way, and use an exhaust valve, but in stock size you may want to compare your stem DIA's as aot of times the exhaust stem is skinnier on the stock size valves. If you had to go "oversize" on your valves due to guide wear, they actually just sell you the exhaust valve for the intake anymore. They do that in the small frame H engines as well up to 3.5HP as they use same size valves too.