Triumph Repair: Further question on blown head gaskets, blown head gaskets, surface gauge

Question
Dear Mr Fitzcharles

The head was torqued to 46 ft lbs and was retorqued. Both times the engine was cold. The bolts were also tightened in the proper sequence.  However, I do not know what the specifications are for the thickness of the ring around the cylinder bore and the depth of the fly cut  grove in the block at each cylinder.  If you are able would you please tell me those numbers.
Thank you in advance

Answer
Sorry Jim, you need to measure them as you said the block was surfaced and an unknown gasket was used. You just want to measure the fly cut grove dept and the gasket that will be put in and see that there is an interference fit so as to put a load on the ring and be sure the gasket is installed with the ridge pointing down into the grove. I have not found where the factory has quoted that dept.

It is hard to believe a head gasket can blow in 300 miles with a proper torque and surfaced head and block. That just don't make sense. don't forget to use a surface gauge on the block and the head to be sure the machine company didn't make a hollow in that area when they surfaced the head and block.
Howard