A description of the cleaning of the piston heads prior to installing new head gaskets included this warning: "be careful you do not break off the carbon lip at the top of the cylinder sleeve."

The description comes from a long, detailed tutorial on head gasket replacement on the Bosch 4.0 engine of a Range Rover P38. What is the carbon lip?

 

X1 .......... too true, unless you are honing the bores and replacing the piston rings the carbon bore step is best left to seal at TDC.

 

Just don't touch the cylinder walls. Use a honing stone on the block mating surface(the fine side) but don't go past the flat mating surface.