In early 2009, my mechanic sent my BMW M6 head to Clearwater Cylinder Heads (CCH) for repair/reconditioning. When it was returned, several of the new valves turned out to be the wrong ones. Unfortunately, this was not discovered until the engine had been put back together and was having its valves adjusted. So my mechanic had to pull the head off, order the correct valves from BMW, have the seats reground, and replace the head. Although Clearwater claims to "guarantee" their work for one year, they would neither correct the situation nor pay my mechanic for the cost of their mistake. Buyer beware of CCH!! read full review »