1981 K20 Project - The Blue Ox

[classicsteel75]

I'm no engine expert but to me it appears you have plenty of thread left to ensure that the new sensor won't come loose. Hard to tell from the pic but there are at least a few threads down under where it's broken off? If that's the case I would screw in the new sensor using thread seal, then use JB Weld to fill in the missing cast iron some. If you use the right JB Weld type, it's amazing how strong that stuff can be. Be sure to clean the area well probably with acetone or something similar before applying.