8k rpm ...

Post up your tire size and gear ratio. Then we will know how accurate your tach is. I say it's junk.
Please
My buddy Mark H campaigned a stock bodied Duster with a destroked 340, that I’ll admit wasn’t all that quick, would routinely have the mechanical telltale tach stuck on 11,500-12,000 rpm. He claimed 13,000 but I saw the tach after a pass many times.