35. Cylinder Head Clean and Inspect
1. Clean top of pistons and top of block:
a. Turn the crankshaft and bring each piston to top dead center (TDC). Using a gasket scraper, remove all the carbon from the piston top.
IMPORTANT: Cover front of engine with a shop towel to prevent debris from entering engine.
b. Remove all the gasket material from the top of the block using a plastic or wood scraper.
CAUTION: PROTECT YOUR EYES WHEN USING HIGH PRESSURE AIR.
c. Blow carbon and oil from the bolt holes.
NOTICE: Intake and exhaust manifold stud threads can be damaged during removal and must be replaced when a new machined cylinder head casting is installed.
NOTICE: Be careful not to scratch the aluminum surfaces when cleaning the cylinder head.
2. To remove gasket material, use a plastic or wood gasket scraper. Remove all gasket material from the manifold and head surfaces.
3. Using a wire brush, remove all the carbon from the combustion chambers.
4. Using a valve guide bushing brush and solvent, clean all the valve guide bushings.
5. Using a soft brush and solvent, thoroughly clean the cylinder head:
a. Intake and exhaust parts.
b. Intake and exhaust valve seats.
6. Inspect cylinder head for flatness. Using a precision straight edge SA9177NE (or equivalent) and feeler gauge SA91101NE (or equivalent), measure the surfaces contacting the cylinder block and manifolds for warpage. If warpage is greater than maximum, replace the cylinder head.
MAXIMUM WARPAGE SPECIFICATIONS:
Cylinder Block Side: 0.05 mm /100 mm (0.0020 inch /3.937 inch)
7. Inspect cylinder head for cracks. Using a dye penetrant, check the combustion chamber intake and exhaust ports, head surface, and the top of the head for cracks. If cracked, replace the cylinder head.
8. Clean the valves:
a. Using a gasket scraper or wire brush, remove all carbon from the valve head.
b. Using a wire inrush, thoroughly clean the valve.
NOTICE: Small scratches, scores or scuffs on the valve stem will damage and wear out the valve stem seal. Always lubricate the valve guide and valve stem before installing a new valve stem seal. If a valve stem seal is removed after installation, it must be discarded.
9. Inspect valve stems and guides for wear, scratches, and burrs:
10. Replace the spring if the spring length is less than 34 mm (1.338 inch) when subjected to a compressive force of 252 N (56.6 lbs.).
11. Perform the following steps to inspect the valve stem-to-valve guide clearance:
- Clamp the J-8001 Dial Indicator Set on the exhaust port side of the cylinder head.
- Locate the indicator so that the movement of the valve stem from side to side (crosswise to cylinder head) will cause a direct movement of the indicator stem.
- Measure the valve head with the valve protruding 10 mm (0.39 inch) from the seat.
- Drop the valve head about 10 mm (0.393 inch) off the valve seat.
- Use light pressure to move the stem of the valve from side to side to obtain a clearance reading.
- The intake valve clearance should be 0.030 - 0.057 mm (0.001 - 0.0022 inch).
- The exhaust valve clearance should be 0.030-0.057 mm (0.001 - 0.0022 inch).
- Measure the valve stem in three locations if the valve clearance is out of specifications.
- Compare the lowest measurement to the specification below.
- Intake valve stem: 5.955 - 5.970 mm (0.2344 - 0.2350 inch).
- Exhaust valve stem: 5.945 - 5.960 mm (0.2340 - 0.2346 inch).
- Replace the valve if the valve stem is out of specification.
- Ream the valve guide and use an oversized valve if the valve stem is within the specification.