There are several "two part" epoxy systems available for sealing low pressure cracks. I have seen a couple advertised claiming to seal combustion chamber cracks but the ones I tried in my youth (still on the market in 2003) FAILED miserably.
As to the red pepper---Come on guys let's not go off on that bent again. We all know that pepper, sawdust, copper powder, aluminium powder, egg whites, ---- on and on and on, ad infinitum, can seal up the "45 caliber hole" in the radiator. That stuff would get you home in a Model A but boy, did you have a clogged up radiator. Todays radiators are quite intolerant of these old time "cures". Unless you have a "need" to experiment and a deep pocket, stick to the "repair or replace" doctrine on the new stuff. It is not at all uncommon to put some magic potion in the radiator to stop a leak "temporarily" and forgetting until the thing costs you an engine or worse.
Rod