I think Mav06 might be on to something...it could just be a lubrication issue at startup caused by an inefficient anti-drainback valve in the oil filter you are using. When you change oil, the new filter has no oil in it at first, so that's a good simulation of what a leaky anti-drainback valve in the oil filter would sound like. I described all this in greater detail in my post here:

https://blazerforum.com/forum/showth...ght=oil+filter

If that's the issue, then just changing to an oil filter with a good anti-drainback valve might cure it for you. Hope this helps.

MrBill99

 

I had the same problem on my 2000 4.3 blazer, put valvoline 10w-30 oil in it and solved problem.