Suzuki 2000 Grand Vitara SQ625 Service Manual page 290

6A1-48 ENGINE MECHANICAL (G16 ENGINE)
D Flatness of gasketed surface:
Using a straightedge and thickness gauge, check surface at a to-
tal of 6 locations. If distortion limit, given below, is exceeded, cor-
rect 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 in.)
D 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 in.)