During IndyCar warm-up on Sunday in Detroit, Chevrolet General Motors president Mark Reuss confirmed the root cause of the issue behind a rash of engine changes in the IndyCar garage. <br>"We had a supplier issue with the valve and the valve guide, and it's a coating issue," Reuss told IndyCar on FOX. "And so if you can imagine the valve sitting in the guide with the wrong coating, over time ...<a class='more' href='https://www.motorsport.com/indycar/news/chevrolet-reveals-cause-behind-flurry-of-indycar-engine-changes-in-detroit-/10825788/?utm_source=RSS&utm_medium=referral&utm_campaign=RSS-ALL&utm_term=News&utm_content=www'>Keep reading</a>