I have a 1992 Chevy S 10 Pickup V6. We drill a 3/8 inch hole through the firewall, and into the engine block. Punctured the coolant cavity in the block. We drilled the hole out to 7/8 inch and plug it with a rubber expansion stopper like gasket and gasket sealant but I’m not sure that will hold. Can we cut a larger hole in the fire wall big enough to spot welled the 7/8 hole in the engine block then weld a cover on the fire wall?
Maybe. I would go to Ace Hardware and get one of those metal plugs that you screw in, using a hex wrench, and a tap to form the threads.
Is this something like a science project? I certanily can’t speak from experience in this area. Perhaps I am judging to fast,was this a attempt to clean out the water jackets of the engine or some other cleaning out work? I have seen that DexCool (but it was later than 92) get stubborn to get out (used chemicals and flushing techniques) but accidently drilling a hole in the engine, I have never been there.