From what I was told, most GTV6 and a few of the earlier Milanos (mine) used cast iron type valve guides, which were documented to occasionally cause sticking or slow valve operation under very high engine temperatures and high RPM. Perhaps they would expand and become smaller in the ID? Later engines had different guides.
I cannot confirm exactly what caused the breakdown, but it also could have been due to weak valve springs, allowing valve "float," although the engine had just 80k miles on it.
It was a very HOT day at Willow, air temp must have been 105 and believe me...I'll never, never go to a track during weather like that again. It was very tough on both car and driver. Gimme a cool cloudy Oregon day...
My first track day was at the streets too, and it was just as hot! Although my friend that I brought along was complaining how hot it was, I didn't even notice it because I was so excited to be out on the track. When I was driving, the temperature indicator was blinking most of the time, but I never let it go over a certain point. I've fixed most of the overheating problem now. I also faded the brakes so badly, I've never been able to get the pedal back, even after bleeding atleast 5 times since then. I have ABS.
BMW's are the ultimate driving machine!
I'm kidding -- please don't ban me.
I'm kidding -- please don't ban me.