Mike used a 130 amp mini welder to make the repair, to demonstrate a worst case scenario for using our electrodes. A cast iron exhaust manifold from a Cummins diesel truck was headed for the junk pile because the shop did not have a cast iron welding rod to repair it. At a cost of $400 to replace, our 77 and 72 rods were an inexpensive alternative. We did not preheat the part and experienced no re-cracking when the weld had air-cooled.