[Ronnieroadster]

The following is actual results on sealing cracked Ford flathead blocks. I have had perfect results using sodium silicate also know as water glass. The numerous sealers you listed above use sodium silicate as the sealer. Most of those sealer are mixed with water and a color additive. Read the directions on use for the above sealers all of them will say to be mixed with water. What i have learned using the sodium silicate directly not reduced or watered down a crack will seal quickly when its put into the radiator filled with water. A few of my Ford flathead race blocks have experienced cylinder cracks from the extreme nature of the racing i do using the sodium silicate i have extended the use of these blocks for many more runs and records. I also bring some with us to a race when i run the car just in case. You can buy a gallon of it on Ebay for less money than most of those sealers you listed. Take the time to read on line about sodium silicate and the many uses for it theres a number of examples for sealing leaks in engines and other systems holding water/coolant. Sodium silicate becomes a coating of glass when it flows into the crack once it reaches a temp of 140 degrees.
Ronnieroadster