Are you getting coolant into the oil again? The sodium silicate cures best when it's exposed to combustion heat. You might want to try regular Bar's Leaks on that type of crack, the one that seals a leak with vegetable fibers and water-soluble glue. Eventually, you're going to need another block, or have the crack in the present one repaired professionally. A 4 lb. cap will force more sealer into the crack. A zero pound cap only uses gravity flow to get the sealer where it belongs. Warm up the engine with the 4# cap, then let it sit overnight without relieving the pressure.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!