You don't need to waste time and money buying a 27mm socket.
27mm is 1.0630 inches. 1 1/16 is 1.0625 inches. The engine is not going to care about the difference. I got a 1 1/16 standard socket from Sears and it works just fine. The real problem is the reach in from the forward face of the crank pulley. This requires just the proper length extension. If the extension is too long, the socket wrench hits the fan shroud. If the extension is too short, the socket wrench hits the pulley before you reach the bolt. From memory, I think that the 1.5 inch extension was about right.

Brian Carlton