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6A2-66 ENGINE MECHANICAL (M13 ENGINE)
• Check cylinder head for cracks on intake and exhaust ports,
combustion chambers, and head surface.
Using a straightedge and thickness gauge, check flatness of
gasketed surface at a total of 6 locations. If distortion limit,
given below, is exceeded, correct gasketed surface with a
surface plate and abrasive paper of about #400 (Waterproof
silicon carbide abrasive paper): place abrasive 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 for cylinder head surface on piston side
: 0.03 mm (0.001 in.)
• 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 for cylinder head surface on intake and
exhaust manifold
0.05 mm (0.002 in.)
Valve springs
Valve spring free length and preload
Referring to data given below, check to be sure that each spring is
in sound condition, free of any evidence of breakage or weaken-
ing. 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
Standard: 36.83 mm (1.450 in.)
Limit: 35.83 mm (1.411 in.)
Valve spring preload
Standard: 107 – 125 N (10.7 – 12.5 kg) for 31.50 mm
(23.6 – 27.6 lb/1.240 in.)
Limit: 102 N (10.2 kg) for 31.50 mm (22.5 lb/1.240 in.)
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