Hmm, 8,000 rpm on the old 3W-100 with a 27x10?
Mine "only" turns a Mejzlik 27x10 at 6400 rpm.
Haven't ever seen a non-TOC version turn very much stronger.

I bet a lot of guys at your field like to borrow your "happy tach".
Makes their engines seem so much more powerful....

Seriously....8,000 rpm with a 27" prop would make the loudest ripping prop noise you can imagine on the ground. Your ears would still be bleeding from pointing the tach at it.

Even a DA-150 or 3W-150 QS-TOC could not turn a 27x10 prop at 8000 rpm. It requires about 19.4 HP to turn that rpm according to thrust calculator (and that's close enough for government work).