I got a D15B7 that was running really rough- I was told it had a blown motor, which I had an extra. When I took the motor out and took off the head two valves were missing chunks out of the edge of the valve, no wonder it ran crappy. I thought it was because of a timing belt issue and the valves hit the piston, but because they broke where they did, it still turned and ran. Maybe something else broke the valves ??? Or is that what a burnt valve is? Anyway, next time time you get frustrated just park it out front and I'll get it.