4 years ago I had a 1979 ford f150 4x4, it had a 351m. the engine was bad and i had to trade it, i want another one I miss my truck. my questions are thies motors have flat tap cams and need a lot of zink in the oil. would you trust a old motor that is orginal with low miles? what about if they did not add zink? if they rebuilt the engine and the cam is broke in, and they changed oil but dint put zink back would it hurt it? Last question, if they used newer oil and put zink in it...will it still hurt the cam loabs with the ditergent in the oil?