/forums/images/graemlins/angryfire.gif /forums/images/graemlins/thumb.gifYou can use 12 inches of 2" copper tubing and 16 inches of ½&#8221; copper tubing, two 2&#8221; copper caps, four brass ½&#8221; pipe x ½&#8221; barbed fittings, and a propane soldering kit, which can be found at some hardware stores like Eagle or Lowes. The plan would be to solder the 2&#8221; caps onto a 12&#8221; piece of the 2&#8221; tubing. Next drill a hole in each cap, dead center and insert and center a 16&#8221; piece of the ½&#8221; tubing. Next solder the ½&#8221; tubing where it comes out of each cap. Next drill a hole on the side of each cap and solder a brass ½&#8221; barbed fitting into each hole. You will have to solder a barbed fitting to each protruding piece of ½&#8221; tubing also. Run the engine coolant through the ½&#8221; tube (tube side) and the fresh water through the 2&#8221; pipe (shell side). You now have a simple heat exchanger.