3800 head bolts keep breaking

Head bolt on rear head keeps breaking before reaching torque spec. any help would be great. 3.8 v6 06 Grand Prix.

RE: The cylinder head bolts are ‘torque-to-yield’ bolts that have a basic torque spec then an additional angle reading to achieve the desired clamping force. You are required to use new bolts when replacing the head or head gaskets, etc. If the bolts are breaking, you are either using the wrong or old bolts, not doing the right sequence of tightening, or over-tightening. These bolts never usually break, so I’d look at your parts or try a different torque wrench and use the proper specs.