[BillK]

Chris,

There is a service bulletin having to do with a "ticking" noise when hot but I really think that the noise you have is much more than what they are describing in the bulletin. I have to agreee with the others that it sounds like a rod bearing, maybe wrist pin, etc. Definitely sounds piston related rather than valve train.

I checked on another automotive site that I have access to and found a lot of valve train noise issues but only one with a knock that "sounded" like yours. This one had a piston hitting the crankshaft counterweight, probably due to a hydrolock slightly bending the rod. If you can isolate it to one cylinder, maybe see if you can look down through the spark plug holes and see if it is cleaner than the rest ? A borescope would be nice. If it had a leaking head gasket and got water into the cylinder this would be a possibility. How was it running prior to the fuel pump issue ?