Cylinder Head Reconditioning
CYLINDER HEAD RECONDITIONING
Tools Required:
J 8001 Dial Indicator Set
J 8062 Valve Spring Compressor.
J 8101 Valve Guide Cleaner
J 9666 Valve Spring Tester
J 37377 Valve Guide Reamer 0.089 mm (0.003 inch) OS.
J 37378 Valve Guide Reamer 0.394 mm (0.015 inch) OS.
J 37379 Valve Guide Reamer 0.775 mm (0.030 inch) OS.
Important
^ Before removing the cylinder head(s) from the engine and before disassembling the valve mechanism, perform a compression test and note the results.
^ During disassembly of the cylinder head, be sure that the valve train components are kept together and identified so that they can be installed in their original locations.
Disassemble
1. Spark plugs (221).
2. Right cylinder head engine lift hook bolts (201).
3. Engine lift hook (200).
4. Intake manifold mounting stud (140).
5. Rocker cover studs (196).
6. Compress the valve springs (128 and 135) using J 8062.
7. Valve locks (131 and 139).
8. Valve caps (130 and 138).
9. Exhaust valve oil shedders (137).
10. Valve springs (128 and 135) and dampers (127 an 134).
11. Spring shims (133), if equipped.
12. Intake valve stem oil seals (126).
13. Valve stem 0-rings (129 and 136).
NOTICE: Avoid damaging the valve guide. If the valve stem has mushroomed due to wear from the rocker arm, remove burrs by chamfering the valve stem with an oil stone. Do not remove the valve from the guide with a hammer and punch.
14. Valves (125 and 132).
15. Rocker arm studs (121) and pushrod guide plates.
16. Water jacket plugs.
Inspect
^ Cylinder head gasket and mating surfaces for leaks, corrosion and blow-by. If the gasket has failed, determine the cause:
A. Improper installation.
B. Loose or warped cylinder head.
C. Missing, off location or not fully seated dowel pins.
D. Low torque on cylinder head bolts.
E. Warped case (block) surface.
F. Scratched surfaces.
G. Excessive inlet manifold torque.
H. Cracked engine block tapped holes.
Clean
CAUTION: Safety glasses must be worn when using a power wire brush to avoid damage to the eyes.
1. Cylinder head bolts (115).
2. Cylinder head (113).
- Carefully remove all varnish, soot and carbon to the bare metal.
- DO NOT use a motorized wire brush on any gasket sealing surface.
3. Valve guides as shown in Figure 51.
4. Valves (125 and 132) of carbon, oil and varnish.
^ Carbon can be removed with a wire brush.
^ Remove varnish by soaking in carburetor cleaning fluid.
^ Do not scratch the valve stem with the wire brush.
5. Threaded holes.
6. Remains of sealer from plug holes.
Inspect
1. Cylinder head bolts (115) for damaged threads or stretching, and damaged heads caused by improper use of tools.
Important: Suspect bolts must be replaced.
2. Cylinder head (113) for cracks, especially between valve seats and in the exhaust ports.
3. Cylinder head deck for corrosion, sand particles in head, and porosity.
Important: Do not attempt to weld the cylinder head, replace it.
4. Cylinder head deck, intake and exhaust manifold mating surfaces for flatness as shown in Figure 52. These surfaces may be re-conditioned by milling.
- If the surfaces are "out of flat" by more than 0.1mm (0.004 inch), the surface should be milled.
- If more than 0.25 mm (0.010 inch) of metal must be removed from the head, it should be replaced.
5. All threaded holes for damage.
- Threads may be reconditioned with thread inserts. Refer to "Thread Repair".
6. Cooling jacket plugs seating surfaces.
7. Valve seats for excessive wear and burned spots.
^ Since the valve guide serves to support and center the valve grinder, it is essential that the valve guide is cleaned properly. If the valve guide requires reaming, measure valve guide clearance to determine if an oversized valve will be required. This procedure must be performed before valve seats can be reconditioned.
^ If a burnt valve condition exists, it may be necessary to recondition the valve seat. At no time should there be less than 4 mm of valve seat material remaining after reconditioning.
^ Valve seats may be reconditioned by grinding. Follow the grinder manufacturer's instructions. Refer to "Engine / Specifications" for seat angles. If, after grinding, the new seat is too wide, it may be narrowed by using a 70° stone. The 70° stone will raise the seat.
8. Valve stem tip for wear.
9. Valve lock (131 and 139) and oil seal grooves for chipped or worn lands. Replace the valve if chipped or worn.
10. Valve face for burning or cracking. If pieces are broken off, inspect the corresponding piston and cylinder head area for damage.
11. Valve stem for burrs and scratches. Burrs and minor scratches may be removed with an oil stone.
12. Valve stem for straightness and valve head for bending or distortion. Use "V" blocks. Bent or distorted valves must be replaced.
13. Valve face for grooving. If the groove is so deep that refacing would result in a knife edge, the valve must be replaced.
14. The valve face may be ground to specifications if it is otherwise in good condition. If the valve face cannot be grounded within the limits given, it must be replaced.
15. Valve spring dampers (427 and 134) for broken pieces or cracks. Replace if damaged.
16. Valve springs (128 and 135).
^ Free length.
^ Spring ends. If they are not parallel, the spring is bent and must be replaced.
^ Spring tension (load open and load closed). If below specification, replace.
^ For cracks or breaks.
17. Valve spring seating surface of the spring caps for wear, cracks or gouging. Replace as required.
Measure
1. Valve margin after grinding valves.
- If the margin is less than the minimum recommended margin, replace the valve.
2. Valve seat margin and runout.
- If the margin is less than the minimum recommended margin, replace the cylinder head.
3. Valve guide clearance.
^ Insert the valve into its guide. Lift it 2 mm (1/8 inch) off the seat and move it side to side, measuring the amount of movement with a dial indicator.
-OR-
^ With a hole gage, measure the valve guide ID, then measure the valve stem with a micrometer and compare the clearance.
NOTICE: Avoid breaking reamer flutes or jamming the reamer into the valve guide due to packing of chips or carbon. Clean the valve guides before reaming.
^ The valve guides may be reamed oversize and an oversized valve installed (Figure 56).
Assemble
1. Lightly lap the reconditioned valves into the valve seat.
2. Cooling jacket plugs. Coat plugs with sealer GM p/n 1050026 (or equivalent).
Tighten Plug to 21 N.m (15 lb. ft.).
3. Pushrod guide plates and rocker arm studs (121)
Tighten Studs (121) to 46 N.m (35 lb. ft.).
4. Valves (125 and 132).
Measure
^ Valve run-out. Lift the valve off its seat and apply a dab of Prussian blue on the valve face. Seat the valve and carefully rotate it. The Prussian blue traces transferred to the valve seat are an indication of concentricity of the valve seat.
^ Clean all traces of Prussian blue. Apply a dab of Prussian blue on the valve seat and repeat the check. The traces of Prussian blue transferred to the valve indicates valve run-out. Recondition valve seat/face or replace valves as required.
5. Intake valve stem oil seals (126).
Important Push the valve stem seals down as far as possible. If oversize valves have been installed, oversized valve stem must be used.
A. Use plastic sleeve provided.
B. Press over valve guide boss.
6. Spring shim (133), if required.
7. Valve stem 0-rings (129 and 136).
8. Valve spring dampers (127 and 134) and springs (128 and 135)
9. Exhaust valve oil shedders (137).
10. Valve caps (123 and 138).
11. Compress the valve springs (128 and 135) using J 38606.
12. Valve locks (131 and 139).
- If necessary, hold valve locks in place with grease.
13. Release valve springs (128 and 135).
Inspect
^ Make sure valve locks are seated.
14. Rocker cover studs (196).
Tighten Studs (196) to 12 Nm (106 lb. in.).
15. Intake manifold mounting studs (140).
Tighten Studs (140) to 10 N.m (89 lb. in.).
16. Right cylinder head engine lift hook (200) and bolts (201).
Tighten Bolts (201) to 32 N.m (24 lb. ft.).
NOTICE: To avoid damage, install spark plugs (221) after the cylinder head has been installed on the engine block assembly.