Yes, that's the gruesome part. They also ruined the housing that bolts up to this. In order to get a bolt to align with the mis-aligned threads they had to opening up a 5/16 hole to 3/4 so the bolt would fit.Was that a helicoil that missed by 75% of the bolt diameter?? Ugly. At least you had decent access.. Good fix by you though.
Filler is JB Weld, its a two-part epoxy used to make repairs to metal and other materials. They make a variety of fillers and adhesives. It's good to work with and can be cut or machined as needed. A grid heater is a cold starting aid used in some diesel engines. Think of the heating element in your toaster, does the same thing and heats the air inside the intake manifold. It usually cycles prior to starting the engine so the initial dose of air is warmed up. Glow plugs perform the same type of function but those are installed in the combustion chamber.Finished looks sweet. What’s the filler?
Btw, what’s a grid heater?