About 25 yrs ago, both me and the wife were both down with the flu for about a week in the middle of winter. Well the engine blocks busted in both my truck and jeep. Both had SB Chevy engines. I found the cracks. Welded most of it with nickel rod. I then pulled a vacuum on the water passages and put JB weld all over the cracked area. Sealed up Good! I have since sold the truck, when they started up emissions testing. I wasn't about to put all that emissions crap back on the truck. I sold it to someone who was taking it to Mexico. I still have that engine in my 53 Willys Jeep. No water leaks at all.
JB Weld(epoxy) works good.
I now have all sorts of thickeners for epoxy resin. Aluminum, graphite, micro balloons, fumed silica, wood flour, chopped glass fibers, you name it, I may have it. That way I can take basic epoxy resin and modify it to my needs.