Engine Inspection and Repair
Thoroughly clean and dry all engine components prior to inspection. Be careful not to damage the joints or friction surfaces of aluminum alloy components (such as cylinder head or pistons).
CYLINDER HEAD INSPECTION
Replace cylinder head if any wear or damage is evident. Measure cylinder head distortion using suitable tools. If distortion exceeds .006 inch (.15 mm), grind the mating surface. Do not grind off more than .008 inch (.20 mm) from cylinder head.
On 12 valve engine, measure manifold distortion. If distortion exceeds .006 inch, grind the surface or replace cylinder head.
VALVE INSPECTION
Inspect valve stem for wear or damage and replace as necessary. Check valve face for damage or roughness. Minor damage can be corrected by refacing the valve. Measure valve head thickness and stem diameter. If valve head thickness exceeds .020 inch (.5 mm) on intake valve, or .039 inch (1 mm) on exhaust valve, replace valve. Exc. on 12 valve engine, intake valve stem diameter should be .3161-.3167 inch (8.030-8.045 mm) and exhaust valve diameter should be .3159-.3165 inch (8.025-8.040 mm). On 12 valve engine, intake valve stem diameter should be .2744-.2750 inch (6.970-6.985 mm) and exhaust valve stem diameter should be .2742-.2748 inch (6.965-6.980 mm).
VALVE GUIDE INSPECTION
Fig. 4 Valve guide installation:
Exc. 12 Valve Engine
Measure clearance between valve stem and guide. If clearance exceeds .008 inch (.2 mm), replace valve guide. To replace valve guide, use tool No. 49 0221 251A and knock guide out from side opposite combustion chamber. Install clip onto new guide, then drive guide into cylinder head using removal tool. The clip must just contact cylinder head, .752-.772 inch (19.1-19.6 mm) from end of valve guide, Fig. 4.
12 Valve Engine
Measure clearance between valve stem and guide. If clearance exceeds .008 inch (.2 mm), replace valve guide as follows. Shapes of intake and exhaust valve guides are different. Use exhaust valve guide on both sides as a replacement.
1. Gradually heat cylinder head in water to 190°F.
2. Using tool 490221251A or equivalent, remove valve guide from side opposite combustion chamber.
3. With cylinder head at 190°F, tap valve guide in from side opposite combustion chamber until installed height A, Fig. 4, is .780-.799 inch (19.8-20.3 mm).
VALVE SPRING INSPECTION
Fig. 5 Valve spring angle limit:
Exc. 12 Valve Engine
Inspect valve springs for cracks or other damage and replace as necessary. Measure free length of springs. Free length of outer spring should measure 1.984 inch (50.4 mm) for 1984-85 626 & 1987-88 B2200, 2.047 inch (52 mm) for 1986 B2000 or 2 inch (50.8 mm) for 1986-87 626 and inner spring 1.744 inch (44.3 mm) for 1984-85 626, 1.732 inch (44 mm) for 1986 B2000 or 1.681 inch (42.7 mm) for 1986-87 626 and 1987-88 B2200. Replace springs not meeting specifications. Measure angle limit of springs, Fig. 5. If spring varies more than .07 inch (1.8 mm) for 1984-86 626 and 1986 B2000, .06 inch (1.5 mm) for 1987 626 and 1987-88 B2200 inner spring or .07 inch (1.8 mm) for 1987 626 and 1987-88 B2200 outer spring, it must be replaced.
12 Valve Engine
Inspect each valve spring for cracks or damage and check free length and angle, replacing as necessary. Intake spring free length should be 1.949 inch (49.5 mm) and must not be less than 1.902 inch (48.3 mm). Exhaust spring free length should be 1.984 (50.4 mm) inch and must not be less than 1.937 inch (49.2 mm). Valve spring angle limit must not exceed .067 inch (1.7 mm).
Fig. 6 Valve seat height measurement:
VALVE SEAT INSPECTION
If the valve seat surface which is in contact with the valve face is damaged, it may be repaired by grinding. Ensure valve seat surface which contacts valve is centered in valve face. Measure valve seat height, Fig. 6, which should be 1.831 inch (46.5 mm). On all 1984-86 models, if height is .0196-.0590 inch (.5-1.5 mm) less than specification, insert a washer onto spring seat. On all 1984-86 models, if height is more than .0590 inch (1.5 mm) less than specification, replace cylinder head. On 1987 models and 1988 B2200, if height is 1.850-1.890 inch (47-48 mm), insert a washer onto spring seat area. On 1987 models and 1988 B2200, if height is more than 1.890 inch (48 mm), replace cylinder head. On 12 valve engine, if height is 2.008-2.035 inch (51-51.7 mm), insert spacer between spring seat and cylinder head. If height exceeds 2.035 inch (51.7 mm), replace cylinder head.
Install valve seat using tool No. 49 G030 160.
CAMSHAFT INSPECTION
Fig. 7 Camshaft inspection. Exc. 12 valve engine:
Except 12 Valve Engine
Check camshaft for wear or damage and replace as necessary. Measure cam height and journal diameter and replace the camshaft if not within specifications. Measure front oil seal sliding surface and fuel cam, Fig. 7. Oil seal sliding surface should measure 1.337-1.338 inch (33.961-34.000 mm) and fuel cam should measure no less than 1.4645 inch (37.2 mm). If measurements are not within specifications, replace camshaft. Ensure camshaft runout does no exceed .0012 inch (.03 mm) and camshaft endplay is not more than .008 inch (.20 mm).
Fig. 8 Measuring cam lobe height. 12 valve engine:
12 Valve Engine
1. Place front and rear journals on V-blocks and check camshaft runout. If runout exceeds .0012 inch (.03 mm), replace camshaft.
2. Check camshaft for wear or damage, replacing as necessary.
3. Check cam lobe height at two points as shown, Fig. 8. Intake lobe height should be should be 1.626-1.630 inch (41.29-41.39 mm) and must not be less than 1.620 inch (41.14 mm). Exhaust lobe height should be 1.646-1.650 inch (41.8-41.9 mm) and must not be less than 1.64 inch (41.65 mm).
Fig. 9 Measuring camshaft journals. 12 valve engine:
4. Measure wear of journals in X and Y directions at the two points as shown, Fig. 9. Diameter of front and rear journals should be 1.2575-1.2585 inch (31.940-31.935 mm) and diameter of center three journals should be 1.2563-1.2573 inch (31.910-31.935 mm). Out of round must not exceed .002 inch (.05 mm).
5. Measure oil clearance of camshaft and camshaft caps as follows:
a. Remove any oil or dirt from journals and bearing surface.
b. Place camshaft on cylinder head.
c. Position Plastigage on top of journals in axial direction.
d. Place camshaft caps and rocker arm shafts in position, torquing to specification.
e. Remove camshaft and measure oil clearance at each cap. Oil clearance of front and rear journals should be .0014-.0033 inch (.035-.085 mm) and clearance of center three journals should be .0026-.0045 inch (.065-.115 mm). If clearances exceed .0059 inch (.15 mm), replace cylinder head.
6. Measure camshaft endplay, which should be .003-.006 inch (.08-.16 mm). If endplay exceeds .008 inch (.2 mm), replace camshaft and/or cylinder head.
ROCKER ARM & ROCKER ARM SHAFT INSPECTION
Replace rocker arm or cam if mating surfaces are worn or damaged. Measure clearance between rocker arm and shaft. If clearance exceeds .004 inch (.10 mm), replace rocker arm shaft assembly.
Fig. 10 Cylinder bore measurement:
CYLINDER BLOCK INSPECTION
Check block for cracks or other damage and replace if necessary. Measure cylinder block distortion. If distortion exceeds .006 inch (.15 mm), grind the mating surface.
Inspect cylinder walls for scoring or indications of seizure and rebore or replace as necessary. Uneven wear on upper portion of cylinder wall may be repaired with a ridge reamer. Measure cylinder bore in six places indicated in Fig. 10. Standard bore diameter is 3.3859-3.3865 inches (86.000-86.019 mm). Bore must not be worn more than .0059 inch (.150 mm) and difference between bores must not exceed .0007 inch (.019 mm). If necessary, rebore cylinder and install .010 inch (.25 mm) or .020 inch (.50 mm) oversize piston.
PISTON & PISTON RING INSPECTION
Check outer circumference of piston for scoring or indications of seizure and replace if necessary. Measure piston diameter at right angle to piston pin and below oil ring groove. Standard piston diameter is 3.3837-3.3845 inches (85.944-85.964 mm). Ensure clearance between piston and cylinder wall does not exceed .006 inch (.15 mm).
Replace worn, damaged or broken piston rings. Slide ring into cylinder head and ensure ring gap does not exceed .039 inch (1 mm). Measure ring clearance in piston around entire circumference of ring groove. Maximum ring clearance is .006 inch (.15 mm).
CONNECTING ROD INSPECTION
Check connecting rod for bending or twisting. Maximum allowable twist is .016 inch (.04 mm) per 3.94 inches (100 mm) on 1984-87 626 and B2000. On B2200 and 1988 626 and MX-6, maximum bend or twist is .0024 inch (.06 mm).
Fig. 11 Crankshaft inspection:
Fig. 12 Checking locations for crankshaft wear:
CRANKSHAFT INSPECTION
Check crankshaft for wear, damage or clogged oil passages. Replace crankshaft if runout exceeds .0012 inch (.03 mm). Compare crankshaft measurement, Fig. 11, to the following specifications. On all models, main journal diameter, 2.3597-2.3605 inches (59.937-59.955 mm); crank pin diameter, 2.0055-2.0061 inches (50.940-50.955 mm). On 1984-86 models, rear housing assembly oil seal sliding surface, 3.5412-3.5434 inches (89.946-90.000 mm); oil pump body assembly oil seal sliding surface, 1.3371-1.3386 inch (33.961-34.000 mm). Measure uneven wear on journal and pin at four indicated positions, Fig. 12. Wear should not exceed .002 inch (.05 mm). If wear exceeds limits, the crankshaft may be ground to a maximum of .0295 inch (.75 mm) and an undersize bearing installed. Undersize bearings are available in the following sizes: .010 inch (.25 mm), .020 inch (.50 mm) and .030 inch (.75 mm).
Fig. 13 Flywheel distortion check:
FLYWHEEL INSPECTION
Check flywheel for wear or damage and replace if necessary. Measure flywheel warp using a suitable straightedge, Fig. 13. Warp must not exceed .008 inch (.20 mm). Inspect ring gear teeth for wear or damage and replace if necessary. To remove ring gear, heat gear with torch and tap off flywheel. Prior to installing new ring gear, heat gear to 480-570°F (250-300°C). Ensure beveled side of ring gear faces engine.