Yes it does knock at start up and soon goes away. I'll have that looked into.Please don't quote me on this, but I have a newly installed 4.8 in my truck because the original one had the same problem, and it was due to a cracked head.
Is your engine 'knocking' when first started in the morning, then goes away? If it is, it's the lifter's are not holding there prime due to the antifreeze in the oil. It gets worse the longer you leave it. I found an engine in Ontario with 11,000 Km on it for a replacement, at a better price then buying a head.
The sludge I'm used to seeing is more wet goup, this is more dry looking and rusty in colour. like a metal shovel gets when it sits in the snow.The problem could be as simple as a plugged pcv valve, not letting crankcase gasses out. What color is the sludge?
I'm just getting the old engine apart to see what exactly failed and where. One of the parts counter people at the local GM dealer here is a friend of mine, said there's a flaw in the heads, and the only reason GM didn't recall them was because it was too expensive to hit EVERY TRUCK from 99 to 06 with a 4.8 and those heads.Yes it does knock at start up and soon goes away. I'll have that looked into.Please don't quote me on this, but I have a newly installed 4.8 in my truck because the original one had the same problem, and it was due to a cracked head.
Is your engine 'knocking' when first started in the morning, then goes away? If it is, it's the lifter's are not holding there prime due to the antifreeze in the oil. It gets worse the longer you leave it. I found an engine in Ontario with 11,000 Km on it for a replacement, at a better price then buying a head.
btw, the place I got my replacement from, (in case you are in the same boat) is http://www.sawparts.com/.
They are in Southern Ontario. Seemed to have treated me fairly. Been running the truck for about 2 weeks now, and everything seems to be fine.