Re: case stuffing..
There are other products you can explore. Devcon makes something they call 'Liquid Titanium" and is good for up to 600 degrees F. Even there you'll need to properly clean and prep the surface.
The hazards of this far outweigh any performance gains so be advised that failure of the material to adhere to the casting inside the crankcase can cause fatal damage to an engine. Be careful.
Your idea of using a temperature sensing device is valid as long as the device is a quality tool that will assure accuracy. The inexpensive thermometers I've seen offered might not be give you the accuracy you'll need to determine casting surface temperature. Good thermal sensing equipment is very expensive. Those $20.00 items from some discount tool suppliers won't do the job.
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