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Very NEW here, so maybe this was already covered....

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.

Hope this isn't your problem, good luck with it.
 

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The problem could be as simple as a plugged pcv valve, not letting crankcase gasses out. What color is the sludge?
 

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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.
Yes it does knock at start up and soon goes away. I'll have that looked into.
 

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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.
Yes it does knock at start up and soon goes away. I'll have that looked into.
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.

Don't know how precise the info is, just shop talk possibly, but the more I read online, the more I wish I went with the 5.3 instead of trying to save gas...

Good luck with it;
 
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