Aerio L4-2.3L (2006)
exceeded, correct gasketed surface with a surface plate and abrasive paper of about #400 (Waterproof silicon carbide abrasive paper): Place paper
on and over surface plate, and rub gasketed surface against paper to grind off high spots. Should this fail to reduce thickness gauge readings to
within limit, replace cylinder head.
Leakage of combustion gases from this gasketed joint is often due to warped gasketed surface: such leakage results in reduced power output.
Limit of distortion 0.05 mm (0.002 inch)
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Distortion of manifold seating faces:
Check seating faces of cylinder head for manifolds, using a straightedge and thickness gauge, in order to determine whether these faces should be
corrected or cylinder head replaced.
Limit of distortion 0.10 mm (0.004 inch)
Valve Springs
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Referring to data, check to be sure that each spring is in standard condition, free of any evidence of breakage or weakening. Remember, weakened
valve springs can cause chatter, not to mention possibility of reducing power output due to gas leakage caused by decreased seating pressure.
Valve spring free length
INNER
Standard ........................................................................................................................................................................... 36.08 mm (1.4204 inch)
Limit ................................................................................................................................................................................ 35.00 mm (1.3780 inch)
OUTER
Standard ........................................................................................................................................................................... 40.44 mm (1.5921 inch)
Limit .................................................................................................................................................................................. 39.22 mm (1.544 inch)
Valve Spring preload
INNER
Standard .............................................................................................................................. 6.9 - 7.9 kgf for 27.5 mm (15.2 - 17.4 lbs./1.08 inch)
Limit ..................................................................................................................................................... 6.2 kgf for 27.5 mm (13.6 lbs. /1.08 inch)
OUTER
Standard ......................................................................................................................... 15.4 - 17.8 kgf for 31.7 mm (33.9 - 39.2 lbs. /1.25 inch)
Limit ................................................................................................................................................... 13.8 kgf for 31.7 mm (30.4 lbs. /1.25 inch)
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Spring squareness:
