57. Cylinder Head Clean and Inspect
Cylinder Head Cleaning and Inspection^ Tools Required
- J 8001 Dial Indicator Set
- J 8358 Carbon Removal Brush
- J 284 10 Gasket Remover
Visual Inspection Procedure
1. Inspect the cylinder head for the following:
^ Cracks, damage or pitting in the combustion chambers.
Important: DO NOT machine the camshaft bearing journals.
^ Scoring of the camshaft bearings and/or the journals. If the camshaft bearing journals appear to be scored or damaged, you must replace the cylinder head.
^ Debris in the oil galleries. Continue to clean the galleries until all debris is removed.
^ Coolant leaks or damage to the deck face sealing surface. If coolant leaks are present, measure the surface warpage as described under Cylinder Head Measurement.
^ Damage to any gasket surfaces
^ Damage to any threaded bolt holes
^ Burnt or eroded areas in the combustion chamber
^ Cracks in the exhaust ports and combustion chambers
^ External cracks in the water chamber
^ Restrictions in the intake or exhaust passages
^ Restrictions in the cooling system passages
^ Rusted, damaged, or leaking core plugs
2. If the cylinder head is cracked or damaged, it must be replaced. No welding or patching of the cylinder head is recommended.
Cleaning Procedure
1. Clean all cylinder head surfaces with non-corrosive solvent.
Caution: Refer to Safety Glasses Caution in Service Precautions.
2. Blow out all the oil galleries using compressed air.
3. Remove any carbon deposits from the combustion chambers using the J 8358.
4. Remove any gasket material with the J 2841a
5. Clean any debris or build-up from the lifter pockets.
6. Inspect the cylinder head again for the items noted under Visual Inspection.
Cylinder Head Measurement
Notice: Refer to Fastener Notice in Service Precautions.
1. Measure the camshaft clearance specification using the following procedure:
1.1. Install the camshaft caps.
1.2. Install the camshaft caps bolts.
^ Tighten the camshaft bearing caps bolts to 5 Nm (44 inch lbs.).
1.3. Measure the camshaft bearings using an inside micrometer.
1.4. Inspect and measure the camshaft journal diameters.
1.5. Subtract the camshaft journal diameter from the camshaft bearing diameter in order to obtain the running clearance.
1.6. If the running clearance exceeds the specifications and the camshaft journals are within specification, replace the cylinder head. .
2. Measure the camshaft thrust specification using the following procedure:
2.1. Inspect each camshaft cap thrust surface for excessive scoring/wear.
2.2. Inspect each camshaft.
2.3. Install the intake and exhaust camshafts in the cylinder head.
2.4. Install the camshaft caps.
2.5. Install the camshaft caps bolts.
^ Tighten the camshaft bearing caps bolts to 5 Nm (44 inch lbs.).
2.6. Measure the camshaft thrust bearing clearance at the front camshaft bearing cap. .
2.7. If the camshaft thrust bearing clearance is not to specification repair or replace the cylinder head.
3. Measure the cylinder head flatness using the following procedure:
3.1. Clean any remaining head gasket material from the cylinder head face.
3.2. Place a straight-edge diagonally across the cylinder head face surface.
3.3. Measure the clearance between the straight-edge and the cylinder head using a feeler gage at four points along the straight-edge.
^ If warpage is less than 0.05 mm (0.002 inch), the cylinder head surface does not require resurfacing.
^ If warpage is between 0.05 - 0.20 mm (0.002 - 0.008 inch), the cylinder head must be resurfaced.
Valve Guide Measurement Procedure
1. Measure the valve stem (l)-to-guide (2) clearance as follows:
^ Excessive valve stem-to-guide clearance may cause an excessive oil consumption and may also case a valve to break. Insufficient clearance will result in noisy and sticky functioning of the valve and will disturb the engine assembly smoothness.
^ Clamp the J 8001 to the cylinder head at the camshaft cover rail.
^ Locate the dial indicator so that the movement of the valve stem from side to side (crossways to the cylinder head) will cause a direct movement of the indicator stem. The dial indicator stem must contact the side of the valve stem just above the valve guide.
^ Drop the valve head about 1.6 mm (0.0064 inch) off the valve seat.
^ Use light pressure when moving the valve stem from side to side in order to obtain a clearance reading.
2. If the clearance for the intake valve is greater than 0.11 mm (0.0045 inch) and a new standard diameter valve stem will not bring the clearance within specifications, the cylinder head must be replaced.
3. If the clearance for the exhaust valve is greater than 0.12 mm (0.005 inch) and a new standard diameter valve stem will not bring the clearance within specifications, the cylinder head must be replaced.
4. Valve guide wear at the bottom 10 mm (0.39 inch) of the valve guide is not significant to normal operation.
Valve Spring Inspection and Measurement
^ Tools Required
- J 22738-B Valve Spring Tester
1. Place the valve spring in the J 22738-B.
2. Compress the J 22738-B to the valve open, valve spring compressed, dimension listed in the Engine Mechanical Specifications.
Notice: DO NOT use shims in order to increase valve spring load. The use of shims will cause the valve spring to bottom out before the camshaft lobe is at peak lift and engine damage could result.
3. If low valve spring load is found to be too low, replace the valve spring, DO NOT shim.
Valve and Seat Grinding
Valve Cleaning Procedure
1. Use soft bristle wire brush to clean any carbon build-up from the valve head. DO NOT use a wire brush on any part of the valve stem. The valve stem is chrome plated to provide enhanced wear characteristics. Wire brushing the stem could remove the chrome plating.
2. Thoroughly clean the valve with solvent and wipe dry.
Valve Visual Inspection Procedure
1. Inspect the valve for damage from the head to tip for the following conditions:
^ Pitting in the valve seat area (1)
^ Lack of valve margin (2)
^ Bending in the valve stem (3)
^ Pitting or excessive wear in the stem (4)
^ Worn valve key grooves (5)
^ Worn valve tip (6)
2. Replace the valve if any of these conditions exist.
Valve Measurement and Reconditioning Overview
^ Proper valve service is critical to engine performance. Therefore, all detailed measurement procedures must be followed to identify components that are out of specification.
^ If the measurement procedures reveal that the valve or valve seat must be reconditioned, it is critical to perform the measurement procedures after reconditioning.
Valve Seat Width Measurement Procedure
1. Measure the valve seat width in the cylinder head using a proper scale.
2. Measure the seat width on the valve face (1) using a proper scale.
Important: The seat contact area must be at least 0.5 mm (0.020 inch) from the outer diameter, margin, of the valve. If the contact area is too close to the margins, the seat must be reconditioned to move the contact area away from the margin.
3. Compare your measurements with the specifications listed in Engine Mechanical Specifications.
4. If the seat widths are acceptable, check the valve seat roundness using the Valve Seat Roundness Measurement Procedure.
5. If the seat width is not acceptable, you must grind the valve seat using the Valve and Seat Reconditioning Procedure to bring the width back into specification. Proper valve seat width is critical to providing the correct amount of valve heat dissipation.
Valve Seat Roundness Measurement Procedure
1. Measure the valve seat roundness using a dial indicator attached to a tapered pilot installed in the guide. The pilot should have a slight bind when installed in the guide.
Notice: The correct size pilot must be used. Do not use adjustable diameter pilots. Adjustable pilots may damage the valve guides.
2. Compare your measurements with the specifications listed in Engine Mechanical Specifications.
3. If the valve seat exceeds the roundness specification, you must grind the valve and valve seat using the Valve and Seat Reconditioning Procedure.
4. If new valves are being used, the valve seat roundness must be within 0.05 mm (0.002 inch).
Valve Margin Measurement Procedure
1. Measure the valve margin using an appropriate scale.
2. Reference the specifications for minimum valve margin and compare them to your measurements.
3. If the valve margins are beyond specification, replace the valves.
4. If the valve margins are within specification and do not require refacing, test the valve for seat concentricity using the Valve-to-Seat Concentricity Measurement Procedure.
Valve-to-Seat Concentricity Measurement Procedure
^ Checking the valve-to-seat concentricity determines whether the valve and seat are sealing properly.
^ You must measure the valve face and the valve seat to ensure proper valve sealing.
1. Coat the valve face lightly with blue dye (3).
2. Install the valve in the cylinder head.
3. Turn the valve against the seat with enough pressure to wear off the dye.
4. Remove the valve from the cylinder head.
5. Inspect the valve face.
If the valve face is concentric, providing a proper seal, with the valve stem, a continuous mark will be made around the entire face (1).
Important: The wear mark MUST be at least 0.5 mm (0.020 inch) from the outer diameter, the margin, of the valve. If the wear mark is too close to the margin, the seat must be reconditioned to move the contact area away from the margin.
If the face is not concentric with the stem, the mark will NOT be continuous around the valve face. The valve should be refaced or replaced and the seat must be reconditioned using the Valve and Seat Reconditioning Procedure.
Valve and Seat Reconditioning Procedure
Important:
^ If the valve seat width, roundness or concentricity is beyond specifications, you must grind the seats in order to ensure proper heat dissipation and prevent the build up of carbon on the seats.
^ It is necessary to reface the valve if seat reconditioning is required unless a new valve is used.
1. Grind the valve seats (2) to the proper angle specification listed in Engine Mechanical Specifications.
2. Using the proper angle specification listed in Engine Mechanical Specifications, grind, relieve, the valve seats (1) to correctly position the valve seating surface (2) to the valve.
3. Using the proper angle specification listed in Engine Mechanical Specifications, grind, undercut, the valve seats (3) to narrow the valve seat widths to the specifications listed in Engine Mechanical Specifications
4. If the original valve is being used, grind the valve to the specifications listed in Engine Mechanical Specifications. Measure the valve margin again after grinding using the Valve Margin Measurement Procedure. Replace the valve if the margin is out of specification. New valves do not require grinding.
5. When grinding the valves and seats, grind off as little material as possible. Cutting valve seat results in lowering the valve spring pressure.
6. Install the valve in the cylinder head. If you are using refaced valves, lap the valves into the seats with a fine grinding compound.
The refacing and reseating operations should leave the refinished surfaces smooth and true so that minimal lapping is required.
Excessive lapping will groove the valve face and prevent a good seat when hot.
Important: Be sure to clean any remaining lapping compound from the valve and seat with solvent and compressed air prior to final assembly. If you are using new valves, do not lap the valves under any condition.
7. After obtaining the proper valve seat width in the cylinder head, you must re-measure the valve stem height using the Valve Stem Height Measurement Procedure.
8. If the valve stem height is acceptable, test the seats for concentricity using the Valve-to-Seat Concentricity Measurement Procedure.
Valve Stem Height Measurement Procedure
Important: To determine the valve stem height measurement, measure from the valve spring seat to the valve spring retainer.
1. Install the valve into the valve guide.
2. Ensure the valve is seated to the cylinder head valve seat.
3. Install the valve stem oil seal.
4. Install the valve spring retainer and valve stem locks.
5. Measure the distance (1) between the valve stem oil seal spring seat to the bottom of the valve spring retainer.
6. If the maximum height specification is exceeded, a new valve should be installed and the valve stem height re-measured.
Notice: DO NOT grind the valve stem tip. The tip of the valve is hardened and grinding the tip will eliminate the hardened surface causing premature wear and possible engine damage.
Notice: DO NOT use shims in order to adjust valve stem height. The use of shims will cause the valve spring to bottom out before the camshaft lobe is at peak lift and engine damage could result.
7. If the valve stem height still exceeds the maximum height specification, the cylinder head must be replaced.