Originally Posted by vicious_fishes
hence me asking the question... at the moment, with what i think is 2 layers, i can put my hand on the pipe for a few seconds before needing to let go.
can you elaborate for me mate?
Sorry for the crapy cell phone response earlier.. Many headers have slip joints (where one section of the header pipe slides inside another). Usually the slip joint is contained with a bracket, wire, etc.. Wrapping your headers retains more heat in the header's stainless steel piping. The pipes can get so red hot inside the wrap that the pipe gets soft (while hot) and can easily bend, separate at the seams etc. It happened to me at Pocono long course. A heat-wrapped pipe caused the Perrin header to get so hot that it separated, pulled apart and blew hot exhaust gas all over the radiator, hose, wiring, etc., and even turned the header wrap into glass.. I'll see if I can dig up some shots for reference....
You can see the slip joint on the right (driver's side) in the pic of the header on Perrin Performance's website...