MBE4000 Cylinder head Bolts and stretch bolts generally
The MBE4000 head bolts, because there are stretch bolts, loose their clamping force on reuse, and unless they are strictly within the manufactures stretch limits, should not be used again otherwise leaks will occur.
Stretch bolts, when properly torqued, loose some of their diameter to the stretch, but are elastic, and if variations in the gasket material or other things occur they keep their clamping force by varying their diameter slightly, but frequently, like breathing. The clamping force of stretch bolts is necessary to retain the inevitable variations of cylinder head composite gasket material deformations due to heat etc. and they automatically keep the necessary clamping force on the head gaskets for them not to not leak.
Steve, BDC, Nov 2017
Page Revision #2.1RS 12-18