This project all started when water was discovered in the cylinders of a 1959 John Deere 630 that was purchased in 2006.The head was removed and the cracks discovered. It had been welded before. I stripped and cleaned the head as much as I could without sending it out to have it cooked. That was a mistake and I'll chalk that up as a learning curve for the future, as we all learn by our mistakes. The head was cracked clear across the cumbustion chamber on both clyinders and appeared to have been welded without any preperation and veeing, as the weld was on top of the surface. I removed all the old weld and cleaned the intire surface of any casting skin, which may hold particals of sand from the molding process at the factory. Since this was my first project of this kind, never welded a head with this much damage, I relied on what the code for welding this type of project is. I set up my outdoor, propane cook stove, two burners, and preheated it to what I thought would be the proper temperature, by watching the metal change colors, etc. I remained heating it, at a lower setting, to keep it at the same temperature all through the welding process. I noticed that I was having a problem with bubbles coming through the weld, which really irrritated me. What could be the problem? I made sure I cleaned it properly and done all the right stuff. I continued welding until finnished but all was not well. Just before I got finnished I heard that unmisteakable sound of the head breaking. "Thump".
I have been welding for nigh on to 56 years and have had some schooling from Penn State University where I attended after getting out of high school. I'll have to say the course on welding was not to extensive, meaning, I did not learn it all.
Back to the cracked head again, again, again. I had two questions now that had to be faced. Why did it crack again, and why did it get all those porious holes in the weld? Was it the welding rod? Was it me? What the cathair is going on here? I didn't have all the answers. I talked to other renoun welder people with no help. I traveled to Hagerstown, Md. to talk to the welding supplyer where I have done business for over forty years. While there, I picked up some different welding rods to try.
I started all over again by grinding it back down to a workable piece, grinding all those holes out and making it as clean as possible with a vee notch and all. By now I'm out into the valve seat area in both clyinders. This time I didn't preheat the head as I had done before. I used the old time process of only welding a small weld and peaning it till it cooled. Letting that area alone and welding on the other side where it was cool. I still hadn't answered the question of why all the holes keep coming back into the weld, because it was the same thing all over again. After welding the same area a couple times the hole problem seemed to disapear to a very good and solid weld. Putting all the different aspecks together I figured out what was happening and causing those mischievous holes.
Over a period of time the combustion of fuel forced carbons into the porous nature of the cast iron. Had I cooked the head I probably would have eliminated that problem.
I finished the welding without any further cracking but by the time I finished, I had a rather large mess in both cylinder of the combustion cavities. The roughness was ground down and the valve seats were machined back to standard specifications. I made a jig to do a water test and found a couple of minor holes that a hammer and center punch quickly sealed off.
So much for the cracked head part of this project. I wanted to counter this first because if I couldn't fix the cracks then the rest didn't matter. Before I remover the head I noticed that upon inspection of the whole tractor the exhaust manifold was leaking and somebody had tried to patch it up. What had actually happened was the exhaust gasket burned out and the tractor continued to operate which had caused the hot gases to burn away material on the head itself. Bummer! Well not as bad as it may seem. I'm not one to give up at most anything and this just requires some engineering and a little brain matter to work it out. The obvious answer was to take it to a machine shop and have it plained. The last time I took a two cylinder head to the machine shop, their machine wouldn't handle it. So, I figured to have at it myself. I have one of those drill presses that you buy off of a truck that comes around selling such stuff, and I have made many a tool to do some of the most unbelievable stuff with it. I lathed out a mandrel to fit a nine inch grinding disc, that was for my big Milwaukee hand grinder, to fit into the drill press chuck. I made a jig to mount the head on the drill press table and make the manifold side of the head perfectly level to the grinding disc. With the tables clamping bolt loosened I could swing the table side to side and cover the whole manifold area. The depth of cut was obtained by the spindle's up and down adjustment. Worked beautiful. Since, I have done another one and it worked out the same. The head is back on the tractor and no problems have occurred jet. It has only done moderate work for a couple years since but it runs and operates well.