Never tried high tect Block-sealers, but seen them about. If you rebuilt both heads (valves, springs, etc.)consider starting over with a good short block and your good Top End (and maybe Crank, as reqd.) If ya just paid someone to swap gastets (no machine work-valve job-seals, etc.) and ya want to get a year or so out of it, I sugest ya try the sealers. I think ya must follow label EXACTly (pull T-stat) temp of engine, etc. May work, I just hate to fill good, clean Heads (or a sound block) with Sealer- cant be good for long term cooling or repair!! Were pistons clean and bores free from scratches when Heads last off? You (or GOOD mechanic who did work ) should know condition od heads,pistons, rings, etc.- that opionion should guied in putting more $ in- If repairs to date first rate-consider proper rebuild, if repairs to date “stop Gap” (regardless of cost), try sealer! Your Car, my 2 Cense- been there, et cetera!! Rock on!