COMPRESSION

TM-5-3805-263-14P-2 Grader Heavy Road Motorized Type I Nonsectionalized Type II Sectionalized Manual
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AIR INLET AND EXHAUST SYSTEM TESTING AND ADJUSTING Valve Seat Inserts TM 5-3805-263-14&P-2 Tools needed to remove and install seat inserts are in the 9S3080 Valve Insert Puller Group. For easier installation, lower the temperature of the in- sert before it is installed in the head. Valve Guides COMPRESSION An engine that runs rough can have a leak at the valves, or have valves that need adjustment. Use the test that follows for a fast and easy method to find a cylinder that has low compression, or does not have good fuel combustion. Find the speed that the engine runs the roughest, and keep the engine at this rpm until the test is finished. Loosen a fuel line nut at fuel injection pump to stop the flow of fuel to that cy- linder. Do this for each cylinder until a loosened fuel line is found that makes no difference in engine performance. Be sure to tighten each fuel line nut after the test before the next fuel line nut is loosened. This test can also be an indication that the fuel injection is wrong, so the cylinder will have to be checked thoroughly. Removal of the head and in- spection of the valves and valve seats is necessary. NOTE: The test that follows cannot be used with engines that have pistons with keystone rings. A cylinder leakage test that uses air pressure in the cylinder can be used to indicate the condition of the piston rings, valves and valve seats. Removal of the head and inspection of the valves and valve seats is necessary to find those small defects that do not normally cause a problem. Repair of these problems is normally done when reconditioning the engine. CYLINDER HEAD The cylinder head has valves, valve seat inserts, and valve guides that can be removed when they are worn or have damage. Replacement of these com- ponents can be made with the tools that follow: Tools needed to install valve guides are the 7S8858 Driver Bushing and 7S8859 Driver. The counterbore in the driver bushing installs the guide to the correct height. Use a 1P7451 Valve Guide Honing Group to make a finished bore in the valve guide after in- stallation of the guide in the head. Grind the valves after the new valve guides are installed. Checking Valve Guide Bore Use the 5P3536 Valve Guide Gauge Group to check the bore of the valve guides. Valves Valve removal and installation is easier with use of the 5P1330 Valve Spring Compressor Assembly and 5S1322 Valve Keeper Inserter. 1-59

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