Just some sticky or worn lifter noise. Common. Usually putting in an oil additive to quiet down the lifers helps. Just go to your local parts store and see what they recommend.
I have a 1999 Chevy Blazer all of a sudden today it started knocking if it goes above 2000 RPMs
Search Chevrolet Blazer Questions
Chevrolet Blazer Experts
Related Models For Sale
Used Cars For Sale