All valve systems change dimensions as the temperature of the engine goes from ambient, to full running temp. As this happens, the metal of the engine changes size with temp. (hot bigger, cold smaller) Not all metal changes at the same rate in inches per inch per degree. The valve is made from very different metal than the head. The pushrod and valve rocker are also different. The result is that the valve train expands with heat farther than the head and block. This engine has mechanical valve mechanism that is different than those found in new cars in that those have automatic adjusters which keep the clearance correct. Your tractor has "looseness" that is designed into the system to allow correct operation. This looseness is the clearance. The clearance is more when the valves and engine are cold. The Two ways of setting the valves are when it is cold, and when it is well warmed up. To get it warmed up, and then remove the valve cover and adjust them (while toasting your fingers/hands/and tools) is more difficult, and is usually not done except at repairs that also require the removal of the head. Adjusting cold is a bit less accurate, but no real problem. Setting clearance cold is done as follows: A feeler gauge (a multi-blade tool with 2.5 inch long "feelers" that are in different thicknesses, measured in thousandths of an inch (or mm if Metric) There will be 15 to 25 blades in the tool. The measurement is between the rocker arm and the butt end of the valve. (Adj. Gap in illustration). This gap can have wear between the tip of the valve, and the rocker arm tip. this wear can interfere with correct reading of the clearance if the rocker is cup shaped. Look carefully at a rocker tip to assure it is not grooved. If grooved, it will be necessary to have the tips reground at an auto machine shop. The positioning of the valves is as described in the post. The feel on the feeler gauge is judged good when the gauge has a slight resistance to removal, but is easily inserted. Be careful to keep the feeler flat on the valve butt. The lobe of the cam in the illustration is pointing away from the lifter. This is the position ov adjustment. You cannot see the cam at all, so looking at the opposite valve as directed in the former post is the idea. A valve is open when the lobe pushes all parts and compresses the spring. When it is closed, it is up, and the pushrod is looseish. If this is insufficient instruction, you will need to feed a mechanic about 1/2 pound of steak, and a bottle of 25 dollar Scotch. Jim
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Today's Featured Article - Choosin, Mounting and Using a Bush Hog Type Mower - by Francis Robinson. Looking around at my new neighbors, most of whom are city raised and have recently acquired their first mini-farms of five to fifteen acres and also from reading questions ask at various discussion sites on the web it is frighteningly apparent that a great many guys (and a few gals) are learning by trial and error and mostly error how to use a very dangerous piece of farm equipment. It is also very apparent that these folks are getting a lot of very poor and often very dangerous advice fro
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