Not much info on the 400 temper that I can find past the standard "wheel base, HP, ground clearance, bore x stroke etc" but from what little Ive seen and heard the tempter is basically a savage engine yet it puts out a reported 27hp with +/- 250cc less displacement. Im suspecting that the exhaust port and header restrictions are lessened with the tempter and am curious if a tempter 400 head would fit a ls650 jug. Anyone with (or with access to) a tempter head interested in taking measurements and pictures of the exhaust port? Could end up being an easy swap (even if hard to find) part for better performance for those worried about effing up with a dremel, such as myself.