it does very little good to temp an area that is designed to disipate heat immediately. you want the temp of the motro at combustion point. again also pointing a temp gun at the side of the block does little good as again it is design to eleminate heat. the only way to get a fairly accurate reading of motor temp is at the glow plug. if your using an onboard sensor device i would put it as low as possible on the head. and even there you would probably see as much as a 5 degree difference between it and a temp gun. again depending on which ones you use and the accuracy level og the gun or the on board device.