I fired up the 88 this morning. I wonder if the initial sound was the water pump impeller hitting the front cover. The gasket was destroyed years ago in shipping, it is unique to that reverse rotation pump. I plan on inspecting on removal of the 260 and replacing the water pump anyways, a spare isn't a bad thing. The serpentine belt sounds quiet now, pretty sure the noise is from the passenger side of the motor. Not exactly a knock or clatter exactly. There is a slight exhaust leak on that side. I think it may be wrist pin going. It kind of came and went, now it is more constant. I am thinking wrist pin. Now I plan on upgrading the cooling fan control. I want a direct connection from a toggle switch to override, should I do that from the low fans, thinking so. I plan on getting two, one for into the intake, on a 180, off at 165 and upgrading to a 60 amp relay, since it will fit the current Flexalite contoller. The push in probe didn't work out of box, so I have a 25 amp fuse in between the two terminals, so the low fans come on with the key.