Dave... look into Marine diesel engine repair companies. They do a lot of what is called Sticth Welding it involves grinding out the crack and installing steel studs and then pre heat before welding and post heat after the weld is completed to releive the tension caused by welding...you can try and weld it yourself as there are many great welding products out there but make sure you pick a machinable product as a high nickle content filler metal will make it impossible to machine. You can use your oven at home for the pre and post heat
400 degrees for three hours or as long as the head is 400 degrees all the way through...cold welding can also be done grind out the crack and weld for very short periods if you can't touch it without being burned then you stop and wait until its cooled to the touch...takes a long time and a lot of cleaning between welds and still needs a post heat treatment.... good luck! Steve