[callcoy]

I believe in the JB Weld type material for your application, so does the Automobile and Aircraft industries, among others. The first thing you have to understand is that your cooling system is not pressurized, the water is almost just sitting in the water jackets being pushed around by the water pump. I don't know if one could even find a way to measure if there is any force as the system is more or less open but contained by a lid.

I have a "B" block with the same crack you have discribed, commonly called a freeze crack. I prepared the crack like the others suggested, used the slow set JB Weld. However I didn't do the hammer tapping described. I let it cure for several days then bolted on the pressure testing plates and to experiment, started at 20# with no leaks, when for broke and took it up to 40#. I found no leaks even after trying to get it to fail.

I don't think that a lot of individuals realize that epoxies play a large role in our lives, we wouldn't have many aircraft flying without them. For years all major aircraft mfgs have been bonding planes together, the Air Bus 380 and Boeing Dreamliner are just recent examples. There may not be a car produced today that isn't assembled with the same type of material we are talking about here.

A side note not really related but may be of interest to Model Ar's is an unusual application of JB Weld at Bonneville last year. A fellow I know used it on a aftermarket flathead that is on his Model A powered Lakester. Not only did it hold, but he went 5 mph faster and set a new worlds record.

Oh by the way, if your repair was my block I would add a block sealer after the JB repair, the pour in type just to play it safe. On mine because it was disassembled, I used Irontite heated under pressure for 24 hours.