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Cylinder block
Material................................................................................................ Cast iron
Bore, standard..................................................................................... 96.00–96.03 mm (3.7795–3.7807")
Bore, oversize 1 .................................................................................. 96.300 mm (3.79133")
Bore, oversize 2 .................................................................................. 96.600 mm (3.80315")
The cylinder bores should be bored at a wear depth of 0.10 mm
(0.004 in) (in case the engine has an abnormal oil consumption).
Pistons
Material................................................................................................ Light alloy
3)
Overall height 230, AQ131 .................................................................. 64.7 mm (2.54724")
Overall height 250, 251DOHC, AQ151, AQ171 .................................. 61.7 mm (2.42913")
Height from gudgeon pin center to top of piston
230, AQ131 ......................................................................................... 39.7 mm (1.56299")
Height from gudgeon pin center to top of piston
250, 251 DOHC, AQ151, AQ171 ........................................................ 36.7 mm (1.44488")
Piston clearance, production ............................................................... 0.010–0.030 mm (0.0004–0.0012")
Piston clearance, service .................................................................... max 0.080 mm (0.0031")
Piston, standard dimension ................................................................. 95.980–96.010 mm
4)
(3.779–3.780")
Piston, oversize 1................................................................................ 96.280–96.290 mm (3.791–3.7909")
Piston, oversize 2................................................................................ 96.580–96.590 mm (3.802–3.803")
3)
Maximum weight difference between pistons in the same engine is 16 grams (0.56 oz).
4)
See the spare parts catalog for all the products.
Piston rings
Piston ring end gap (oil scraper ring) ................................................... 0.30–0.60 mm (0.0118–0.0236")
Piston ring end gap (compression ring) ............................................... 0.30–0.55 mm (0.0118–0.0217")
Oversize piston rings 1 ....................................................................... 0.3 mm (0.0118")
Oversize piston rings 2 ....................................................................... 0.6 mm (0.0236")
Compression rings
The upper ring is chromium plated. The lower ring is marked “TOP”.
Number of rings on each piston........................................................... 2
Height, upper ....................................................................................... 1.728–1.740 mm (0.068–0.069")
Height, lower ....................................................................................... 1.728–1.740 mm (0.068–0.069")
Piston ring clearance in groove, upper ................................................ 0.040–0.072 mm (0.0016–0.0028")
Piston ring clearance in groove, lower................................................. 0.040–0.072 mm (0.0016–0.0028")
Oil scraper rings
Number on each piston ....................................................................... 1
Height .................................................................................................. 3.475–3.490 mm (0.1368–0.374")
Gudgeon pins
Full floating pin. Locked at both ends with circlips.
Fit in connecting rod ............................................................................ Light thumb pressure (push fit)
Fit in piston .......................................................................................... Thumb pressure (slide fit)
Standard diameter ............................................................................... 23.0 mm (0.906")
Oversize diameter ............................................................................... 23.05 mm (0.907")
Length ................................................................................................. 65 mm (2.559")
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