ok i recently put a 77 351 in my 91 f-150 and the motor is professionally rebuilt(boiled, bored, honed, and balanced etc...) well a week later the engine started to make a sound that sounds really hollow I can't really describe it but the best I can say is that it sounds like water flowing at a high rate of speed up a copper pipe or something like that, that's the best I can do but anjy help is greatly appreciated and this sounds is really annoying me!!!!