The blow-pipe should not be played over the cylinder walls around the fracture any more than sufficient to bring the edges up to a welding heat. The welding material should not be piled up above the surface as is the usual practice. After cooling, the weld should be smoothed down with a file and scraper. It is best to use soft steel rod for the welding material.
This method has been used in a few cases and was satisfactory in a low-pressure engine. It would not be a success in Diesel engines as the weld usually makes either a low or high spot on the cylinder wall, which would not hold a very high compression, while it would hold quite well with the low-pressure engine.
In the case of cylinders, the two important items that demand attention are the condition Of the water jacket and the lubrication of the cylinder walls. If the jacket be maintained free from scale, and the cylinder be lubricated to the correct amount, the cylinder will take care of itself.
Cylinder Head though it is a seeming paradox, it is true that the best cylinder packing is no packing at all. It seems to be the idea of the average engineer that he must use a thick packing in order to seal the joint securely. Even though it may be demonstrated that, theoretically, the more compressible the packing is the greater the elongation of the studs before "blowing" will occur, in actual practice a thick resilient packing should be avoided. In designs where the head and cylinder flanges are faced straight across, the best possible packing is a thin sheet of copper. This sheet should be annealed and made perfectly smooth and straight. The flange surfaces should be cleaned and, if necessary, smoothed up with emery cloth. The copper gasket, which should also encircle the studs to keep it in place, will maintain a tight seal. A slight blowing on starting is not harmful on a copper gasket and serves to relieve any excessive cylinder pressure. Some engines have this joint grooved for a
copper ring gasket. In replacements the copper wire should be cut, and the ends scarfed and soldered. The wire should also be annealed before using so that it will compress easily. The copper wire gasket, undoubtedly, makes the best seal that can be secured. Some of the better grade engines use a ground joint between the head and the cylinder. If the head was never re moved, this kind of seal is most superior. Unfortunately, it often becomes necessary to inspect the cylinder or remove the piston. It is almost impossible to tighten up enough to reseal this ground joint. Small particles, almost invisible to the eye, will prevent a perfect contact. In replacing this type of-head, it is a good procedure to insert a copper sheet gasket. The use of vulcanized rubber or asbestos gaskets, even with wire insertion, is poor practice. The gasket seldom holds against the pressure, and the blowing of the joint at starting will cause the gasket to tear and be rendered worthless.
A word might be added about the "blowing" of this joint. While it serves to relieve excessive cylinder pressure, the engineer should recognize it as an indication that he has pumped too much fuel into .the combustion chamber on starting. He should give the pump fewer initial strokes on the next starting. If the engine "blows," the operator should retard the fuel pump stroke so that the oil injected is less. On starting an engine, the usual governor, since it is not in a state of perfect equilibrium, will give the fuel pump its greatest possible stroke, even more than full load stroke, and the fuel injected exceeds the capacity of the engine. The pump handle should always be used to hold the pump stroke to a low value, until the engine has come up to speed.