you put the tin foil around the heat sink not the header man honest. And your going to have to re tune it for every weather change even if its only a few degrees. Be careful man winter is the worst thing on your engine if your not sure what to do. Watch the temps closely try to use a lazer temp gun and you might have to adjust the amount of the cooling head that you cover. Winter bashing is a blast man after you bring the rc inside let in sit for about 1/2 an hour then open up your radio tray DO NOT open it right away or you will get condensation in it. and as soon as the engine stops running put the piston at BDC asap! Do not start the engine when its cold heat it up first or start it inside. I bash in the snow for 6 months out of the year its a blast oh and spray some wd-40 on your bearings after you bring it in to prevent rust. Have a blast man