I recently installed new headers on my vehicle. I took out all the old muffler and pipe as it was original to the car, 1968 XR7. So now I need to get the rest of the stuff done and my thinking was to drive it down the hill (I live in the mountains) to the muffler shop and have them finish it up. My dad mentioned that it's possible to damage my engine from the backflow on straight headers/pipes when it's cold. Temps up here have been around 30 at night and 50 during the day. Is this too cold? Do I need to wait until warmer days before driving it down the mountain?