Usage:
The valves and the valve mechanism admit inlet air and release exhaust gases at precisely timed intervals during engine operation.
The engine is of the four-stroke cycle, having four separate strokes required for each cylinder to complete one cycle. The camshaft is timed to the crankshaft and turns at one-half engine speed.
The inlet valve is open during the inlet stroke of the piston to permit air to enter the cylinder. After the compression and power strokes, the exhaust valve is opened to permit the piston, in moving up on the exhaust stroke, to force the burned gases from the cylinder.
Properly adjusted valves will operate for many hours before they need to be reconditioned. Eventually, however, the valve faces and seats can become pitted which ultimately allows compression pressure losses.
Valve rotators cause the valves to rotate while the engine is operating. The rate of rotation is approximately three degrees each time the valve is opened.
This rotation decreases the possibility of excessive carbon deposit build up on the valves.
VALVE AND VALVE MECHANISM (Cross-Section, Single Spring Type)
1-Rocker arm. 2-Locks. 3-Spring. 4-Retainer. 5-Guide. 6-Valve rotator. 7-Push rod. 8-Valve. 9-Bracket assembly. 10-Connector. 11-Valve lifter.
To determine whether a valve rotator is operating, observe the valve spring retainer. If the retainer does not rotate during operation, replace the valve rotator as a unit.
Valve Rocker Arm Assembly
Removal and Installation
Remove the rocker arm cover.
PREPARING TO REMOVE ROCKER ARM ASSEMBLY
1-Nuts. 2-Rocker arm assembly. 3-Oil line.
NOTE: Whenever the rocker arm assembly is removed from the engine, check the valve clearances at installation. Adjust them if necessary with engine stopped. Valve clearances are:
Inlet (cold) ... .015 in.(0,38 mm)
Exhaust (cold) ... .035 in.(0,89 mm)
Disassembly and Assembly
VALVE ROCKER ARM DISASSEMBLY
1-Cotter pins. 2-Washers. 3-Bolts. 4-Spring. 5-Washers. 6-Brackets. 7-Spring. 8-Washers. 9, 10-Rocker arms. 11-Fitting. 12, 13-Rocker arms.
The bearings in the rocker arms should be replaced if the clearance between the bearings and the shaft exceeds .009 in. (0,228 mm).
NOTE: Carefully align the oil holes before the bearing is pressed into place. In order to install new rocker arm bearings properly, an FT193 Driver fabricated tool should be used.
Assemble in the reverse order of disassembly. The supporting brackets should be positioned as shown with the holes for the bolts (3) to the left. Be certain the inlet arms (10) and (13) are installed with the projection (for compression release push rod) toward the exhaust rocker arms (9) and (12) as illustrated. Tighten valve rocker arm assembly retaining nuts to torque of 35 to 45 lb. ft. (4,8 to 6,2 mkg).
Valves
Removal
Compress the valve springs and remove the locks. Release the compressor and remove the retainers, springs, and the valve rotators. The valves can now be removed.
The illustration shows the 5S1330 Valve Spring Compressor Assembly with 5S1329 Jaw (1) in place to compress the valve spring. The 5S1322 Valve Keeper Installer (2) used with the compressor assembly are time savers when installing valve keepers.
COMPRESSING VALVE SPRINGS
1-5S1329 Jaw. 2-5S1322 Valve Keeper Installer.
The valves can also be removed with 7F4292 Valve Spring Compressor Group. The 7F4290 Adapter threads onto a rocker arm stud. When installing the valve springs with 7F4292 Group, use the FT196 Fabricated tool to hold the valves in place.
Cleaning
After removing a cylinder head from the diesel engine and the valve assemblies from the head, carefully scrape all carbon accumulations from the parts. Be sure to clean the valves thoroughly, as well as the valve stems, valve guides and valve ports.
Inspection and Reconditioning
The valves should always be carefully inspected. If the valve faces are pitted or making poor contact with the valve seat, they should be refaced in a valve refacing machine. If the valves are deeply pitted, badly warped or worn they should be replaced.
The wear of the valve stems can be checked by the use of a 0" to 1" micrometer. The valve stem should be measured in three places. Refer to SPECIFICATIONS for valve stem size.
Checking Valve Seats
Coat the valve face with Pressian blue and rotate the valve in the valve seat. Remove the valve and examine the contact pattern on both valve and seat. A line of contact near the top and around the entire circumference of the valve seat should indicate line contact with the valve.
The valve seats can be ground with a valve seat grinding tool. Care should be exercised in its use, as too much material may be removed quickly and unknowingly.
After the valve seats have been ground until they are smooth and concentric with the valve guides, all parts should be cleaned thoroughly.
If the valve seats have been worn or pitted beyond Specifications, the valve seat inserts should be replaced. The 9S3080 Valve Seat Insert Puller Group is used for insert removal. Information regarding the tool group is available upon request. Instructions for its use accompany the group.
See the topic, SPECIFICATIONS, for clearances and tolerances.
Valve Installation
Exhaust valves marked "EX" on the valve head should be installed in the exhaust ports; inlet valves marked "IN" on the valve head should be installed in the inlet ports.
Lubricate the stem and guide for initial starting.
Insert the valve through the valve guide and install the springs and the spring retainer. Compress the springs with a compressor, such as shown in the topic, VALVE REMOVAL. Insert the locks, and tap the retainer lightly as the spring compressor is removed, to make sure the locks (keepers) are seated properly in the retainer.
Valve Guides
The inlet and exhaust valves operate in replaceable valve guides. After the valves have been removed, clean the valve stems and valve guides.
The valve guide wear should be checked with the 1P7452 Valve Guide Measuring Group. Instructions are in Special Instructions GMG00966 for checking valve guide wear.
INSTALLING EARLIER VALVE GUIDES (Diesel and Gas Engines)
1-4H446 Driver. 2-Valve guide.
INSTALLING LATER VALVE GUIDES (Gas Engines)
A-1P7430 Driver for later two-piece valve guides. B-2P2313 Sleeve. 2-Valve guide.
The valve guide (2) can be pressed out of the head using driver (1) for earlier guides and driver (A) for later two-piece guides. The exhaust valve guide is the longer of both earlier and later guides.
The guides should be pressed into place carefully with driver (1) or (A). For earlier guides, run a reamer through the inlet guides to bore them to .4985-.5005 in. (12,66-12,71 mm). Bore the exhaust guides to .5000-.5020 in. (12,70-12,75 mm). Reaming should be done after the guides are installed to insure correct valve stem clearance.
Later gas engine two-piece grooved guides require honing after installation.
LATER VALVE GUIDES (Gas Engines)
3-3N1414 Spacer. 4-Inlet (short) valve guide.
EARLIER VALVE GUIDES (Diesel and Gas Engines)
4-Inlet valve guide.
Tools required for the final sizing are: 1P7451 Valve Guide Honing Group, 1P7452 Valve Guide Measuring Group, 1P7453 Honing Oil, and 1P5571 Brush. Special Instructions (GMG00966) included with the group, explains the sizing procedure.
The spacer (3) for later guides may have a loose or tight fit on the guide. The spacer should seat on the cylinder head.
TOOLS FOR HONING GROOVED VALVE GUIDES (Later Gas Engines)
Valve Lifters
The valve lifters operate in brackets which are attached to the engine block by bolts and locks under the fuel pump and governor drive housings in the V of the engine. The lifters follow the contour of the camshaft lobes and raise the push rods so that valves open and close in the specified order.
Valve Lifter Removal and Installation
1. Remove the inspection covers from the side of the engine and remove the spray tube (1) bolted to the bottom of the lifter.
2. Remove the valve rocker arm covers and remove the rocker arm assembly. See the covering topic.
REMOVING SPRAY TUBES
1-Spray tubes.
3. Remove the fuel pump and governor drive housing from the V of the engine. See the covering topic.
4. Place a wire or large rubber band (9) around the lifters (10) to hold them in place in the bracket.
PREPARING TO REMOVE VALVE LIFTERS AND BRACKETS (D379 Engine Illustrated) (Flywheel Housing Removed for Better Illustration)
2-Lifter brackets. 3-Rocker arm oil lines. 4-Fuel pump and governor drive lube line. 5-Elbow. 6-Push rods.
5. Remove the bolts and locks securing the bracket assembly to the engine block and remove the bracket and lifters (7) as shown.
6. The connector (8) between each bracket can be pushed into the adjoining bracket after removing the bolts securing it to the engine block. The brackets are positioned with two dowel pins and must be lifted straight up to remove them.
REMOVING BRACKET AND LIFTERS (Flywheel Housing Removed for Better Illustration)
7-Bracket and lifters. 8-Connector.
NOTE: Inspect the valve lifters and brackets for wear. If the clearance between the lifter and the bracket exceeds .010 in. (0,25 mm), the lifter or bracket or both should be replaced. If the face of the lifter is damaged, inspect the lobes of the camshaft. Replace the camshaft if necessary.
7. Install in the reverse order of removal, replacing all gaskets and O-ring seals.
LIFTERS HELD IN BRACKET
9-Rubber band. 10-Lifters.
BRACKET AND CONNECTORS
7-Brackets and lifters. 8-Connector.
NOTE: Any of the individual bracket assemblies can be removed independently of the others. Remove the bolts from the connectors (8) on either side of the bracket to be removed and slide the connectors into the adjacent brackets as far as possible. The bracket and lifters (7) can then be removed.
Compression Release Mechanism - (Earlier Engines)
The compression release mechanism opens the inlet valve on each cylinder, allowing the diesel engine to be cranked more easily.
The compression release shaft (4) can be locked in either the RUN or START position. When moved to the START position, the compression release shaft forces the push rods (2) against the inlet valve rocker arms (1), holding the inlet valves (3) open. In the RUN position, the flat portion of the compression release shaft (4) permits normal valve operation.
COMPRESSION RELEASE MECHANISM (Earlier Engines)
1-Inlet valve rocker arm. 2-Compression release push rod. 3-Inlet valve. 4-Compression release shaft.
The compression release clearance adjustments are provided at the upper end of the push rods (2). Set this clearance at .025-.035 in. (0,64-0,76 mm).
Removal and Installation
1. Remove the air cleaner assembly.
2. Remove turbocharger (2) and related pipes.
3. Remove the aftercooler (1). On earlier engines, remove aftercooler cover only.
PREPARING TO REMOVE COMPRESSION RELEASE SHAFT (Earlier Engines)
1-Aftercooler. 2-Turbocharger.
4. Remove the valve covers, rocker arm assemblies, push rods and compression release adjustment rods.
5. Remove the cylinder heads. (D379-front head on right bank, rear head on left bank. D398-middle head on both banks. D399-second head from front on right bank and second head from rear on left bank).
NOTE: Bolt (4) at front of right bank and rear of left bank, positions the compression release shaft laterally. Pawl (3) prevents the shaft from rotating too far but it also limits lateral movement of the compression release shaft.
6. Remove pawl (3).
PREPARING TO REMOVE COMPRESSION RELEASE SHAFT (Earlier Engines)
3-Pawl. 4-Bolt.
REMOVING COMPRESSION RELEASE SHAFT (Earlier Engines)
5-Compression release shaft. 6-Seal.
7. Remove compression release shaft (5).
NOTE: The shaft can be removed at the front of the engine by removing the oil filter housing. The oil seals (6), one at each end of the cylinder block, are usually damaged when removing and installing the compression release shaft.
8. Before installing compression release shaft (5), remove seals (6).
9. Install the compression release shaft.
10. Install new seals (6), with the lips to the inside of the cylinder block. Use care not to damage the seal lips.