A friend wants to remove the cylinder-block brass C.5022 1" Briggs (NPT) Plug (Viart p.158, just forward of the dip-stick) in order to examine the water passage for debris.
Thus far, using a proper Whitworth-sized hex-fitting, no amount of torque and penetrating oil has been adequate to budge it.
Propane torch, several heating and cooling cycles.
If no go:
Oxy/Acetylene torch, several heating and cooling cycles, but go easy as you can wreck something by melting it.
Though I like Gamble’s approach, since debris is suspected, you might wanna knock out a core plug as far forward on the block that would still allow you to inject a strong water stream to clean out the crud. The water jackets pass around the bores so using the intake side may provide the maximum effect.