Well, I dare say it's fast for an aircraft of this vintage which doesn't even have a DI... Agreed, it's probably aerobatic max +6g by the look of it, max perhaps 2525 rpm, which sticks in my mind but from engines which wouldn't fit the bill...
Reference the idea that it might be a crop-sprayer, the black handle on the left with the leather gaiter looks incongruous, and possibly a retrofit.
Anyhow, at least the rotation has stopped... Will C2J ease us out of the dive?