Some TQ's are worth crazy money, 71 340's. Others are worth good money, 1972-75. Some are worth a little money, mostly crummed up with smog stuff. All depends on what it came on. High Performance are more desirable. Earlier the better. As for the leak, the wells could leak, or the special O-rings, Quad-rings, were not used or left out entirely. QuadraJets were notorious for the bowls leaking and epoxy was the cure.
