Got a bit of a riddle on my hands. Bent the exhaust valves on my E36 325i. I removed the head and took it into the engineers. Engineers replaced everything from valve springs to guides etc. My valve stems had to be extended as my cams have been cut. Assembled everything as per normal procedure but had problems like the car not idling, missing etc. Took it in to the guy that tweak the engine for me three years ago. He put it on the dino and everything was fine until he took it onto the road. He said he pushed it to 5000rpm (limited at 7000) and something went wrong. He did a compression test only to find that cylinder 6 has no compression. Head was removed again, valve was bent on cylinder 6. I'm now being told that the timing might have been off or the car was over reved. Maybe I'm a bit dumb but to me if the timing was off or the car was over reved why didn't cylinder 1 bend valves if cylinder 1 & 6 is top dead centre at the same time.