OK, I would like to run my shorty headers open on my Camaro, but I have two questions.1. I heard valve damage may occur because cold air gets in there. Why isn't this the case with straight pipe exhaust, doesn't the cold air travel to the valves in that case anyway?2. Right now with my headers to off road y pipe I have 2 o2 sensors to throw the check engine light off, and it has worked. If I run open headers, will they still work?
Cold air doesn't get in to damage, but the valve needs a bit of back pressure. The valve will burn, crack or check, or the valve seat will do the same. The common damage is a small w crack on the valve face, which then leaks compression gases into the hot header resulting in erratic backfire and misfiring. The lack of back pressure can be compensated for by richer mixture, or grinding a wider seat. Get used to lapping in valves, or find some high performance sodium valves and stelite seats. You could run dumps, and only open the headers for short blasts.
The valve damage from open headers sounds more like a theory than reality. I, and numerous other drag racers, have run open headers for decades without valve damage. More often than not, it's either the lower end or other parts of the valve train that crap out long before the valves. The O2 sensors will work if they stay hot enough, otherwise you may need to put heated sensors in.
