Originally Posted by Hotrod Lincoln
That's a myth. I've run racing engines with open headers for hundreds of laps with no valve damage whatsoever. Maybe if there was no exhaust manifold at all, there might be a little bit of exhaust valve damage, but even then, the engine would have to be run at wide open throttle uphill for miles.
Jerry
thanks I’m weighing my options to get my truck to a muffler shop

This is no longer fun