CARTRIDGE GP-TURBOCHARGER 7E3854 - Caterpillar

426, 428, 436, 438 LoadersReference: Service Manual Module; Systems Operation, Testing and Adjusting, Specifications; 4.236 Diesel Engine; SENR3114-01.The pistons used in the production, of the 4.236 Diesel Engines used in the above backhoe loaders, are coded with a letter to designate piston projection height. Piston projection height is the distance from the top of the installed piston to the top of the cylinder block, when the piston is at its highest point. Low, medium, and high projection height are designated by L, M, or H respectively. Pistons are selected to provide a "best fit" during production. Only pistons with low projection height, stamped L, are available for parts service. This is done to avoid the possibility of a replacement piston contacting the cylinder head.
When a new piston is installed in place of a damaged piston, reduced piston projection height may be a result. This can result in reduced compression which can result in harder starting.
Whenever a piston is replaced, the piston projection height for all the pistons should be measured and recorded. Determine the figure recorded for the piston with the largest projection height. Subtract this figure from the maximum piston projection specification [0.58 mm (.023")] and record the result. This result is the maximum allowable amount that can be milled of the cylinder head to provide optimum compression.
Determine the figure recorded for the piston with the least projection height. If this is less than the minimum piston projection specification [0.36 mm (.014")], the cylinder head can be milled down the distance the minimum piston projection is below the minimum piston projection specification, provided you do not mill off more than the maximum allowable amount (determined earlier).