I was always told it was bad on the valves to run them with open or headers for extended periods of time. I've never understood it but it was one of those things I heard in trade school that stuck with me lol
our Ford 302 had the tube from the exhaust manifold to choke. it cracked at the manifold,and yes, driving an extended period of time did damage to the valve(s) and seat(s) on that side of the engine.
