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STEP 1
Thoroughly clean the cylinder head and block deck surfaces with solvent. Remove any foreign material, gasket, or silicone with a cleaning pad. Choose a cleaning pad that removes soft material but not metal; this will protect the casting surfaces from damage that more aggressive abrasives and tools can cause.
STEP 2
Use a purpose-made straight edge. Lay the straight edge along the flat cylinder head surface. Try to slide a feeler gauge or thickness gauge between the straight edge and the casting. Any gaps between the straight edge and the surface indicate warpage of the head deck. A general specification allows no more than 0.006" (0.152 mm) of warpage in 12" (30 cm) of casting surface when using MLS gaskets. This means a 0.006" (0.152 mm) thickness gauge should generally be used to check for warpage, but the manufacturer’s specifications should be checked to be sure. Much smaller clearances are permissible on smaller heads used in automobile engines.
STEP 3
Check for warpage in the longitudinal and diagonal directions as well as across the head deck. Follow the chart in this box when measuring.
STEP 4
If the feeler blade is slipped beneath the straight edge and there is little resistance when pulling on the blade, it indicates a depression or warpage of the head surface. If the clearance is beyond specifications, make a service recommendation for the cylinder head to be resurfaced by a machine shop. Note, though, that due to the small clearance space between valves and pistons in diesel engines, very little, if any, material can be machined from the cylinder head to correct warpage. Always check specifications for head thickness if a head has been machined.
STEP 5
Check the cylinder block deck using the same procedures as those used when checking the cylinder head.
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