Ok ...I have a 65 dodge dart GT...upon completeing and adjusting a couple of months ago...I noticed a crack near one of the plugs ...carefully repaired and hidden under a little oil. Before reparing this I managed to overheat the engine and now left with knocking...black smoke ect...I want to rebuild it , but never rebuilt an engine before...I'm not afraid to turn a couple of wrenches and have some time....any suggestions? Vic

Welcome on the board. You say you're not afraid to turn wrenches — that's good! But you also say you've never rebuilt an engine before, so before you decide whether to do it yourself or go another route, get and read these three books.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

You may-be better-off if you purchase a good used or already rebuilt engine and get your "hands dirty" by doing the installation yourself.
DD