F1/Cart/Indy whatever cars generally idle around 9k rpm. I beleive they have three layers of valve springs, rather than the traditional single or dual. Also bear in mind the engines are only designed to last 3 or 4 hours at most. I can't remember how many times I've seen one blow. Honda once made a prototype engine with only 1.5L, yet 900hp. Turbos spooling up to 40psi are amazing.