CLEANING AND INSPECTION

1. Thoroughly clean the cylinder head and cylinder block contact surfaces to remove any dirt, oil or old gasket material.

   Fig. 1: Use a gasket scraper to remove the bulk of the old head gasket from the cylinder head's mating surface

2. Check the cylinder head for distortion in six planes, as shown, by placing a straightedge horizontally and diagonally across the cylinder head, and across each end, while attempting to insert a feeler gauge between the head surface and the straightedge. The permissible limit is 0.006 in. (0.15mm) for 4-cylinder engines or 0.004 in. (0.10mm) for 6-cylinder engines.

   NOTE: If distortion exceeds the limit, measure the cylinder head height. If the height is within specifications, based on the following figures, resurface (grind) the cylinder head surface or replace it.

   • 1978–85 GLC: 3.551–3.560 in. (90.3–90.5mm)
   • 1986–89 323: 4.228–4.236 in. (107.40–107.60mm)
   • 1979–82 626: 4.289–4.293 in. (108.95–109.05mm)
   • 1983–89 626/MX-6: 3.620–3.624 in. (91.95–92.05mm)
   • 1988–89 929: 4.931–4.935 in. (125.25–125.35mm)

     Fig. 2: An electric drill equipped with a wire wheel will expedite complete gasket removal

     Fig. 3: Check the cylinder head for distortion by using a straightedge and feeler gauge along six planes of the block mating surface (as indicated by the straight lines) — 4-cylinder engine

   NOTE: As long as the specified minimum height is maintained, a cylinder head may be ground up to the appropriate maximum amount, as follows:

   • 1978–85 GLC: 0.008 in. (0.20mm)
   • 1986–89 323: 0.008 in. (0.20mm)
   • 1979–82 626: 0.008 in. (0.20mm)
   • 1983–89 626/MX-6: 0.008 in. (0.20mm)
   • 1988–89 929: 0.006 in. (0.15mm)
3. On 1979–82 engines, also check the intake and exhaust manifold mating surfaces for distortion by placing a straightedge horizontally across the manifold, while attempting to insert a feeler gauge between the manifold surface and the straightedge. The permissible limit is 0.006 in. (0.15mm). If excessive distortion is detected, grind or replace the manifold.

   Fig. 4: When checking for warpage, be sure to use a precision straightedge and a feeler gauge

   Fig. 5: Check for warpage at all angles, not just one or two of them

4. On 1988–89 engines, also check the cylinder head's intake and exhaust manifold contact surfaces for distortion in three planes each, as shown. Do this by placing a straightedge across the contact surface, while attempting to insert a feeler gauge between the surface and the straightedge. Repeat for the opposite side. The limit is 0.006 in. (0.15mm) for 4-cylinder engines or 0.004 in. (0.10mm) for 6-cylinder engines.

   NOTE: If distortion exceeds the limit, grind (resurface) the cylinder head contact surface or replace it.

5. Inspect the cylinder head's water passages to make sure they are fully open. If necessary, hot tank the head in a solution that is compatible with aluminum to clean the passages.
6. Inspect the cylinder head bolts for damaged threads and make sure they are free from grease and dirt. Repair or replace any damaged threads or broken studs.

   Fig. 6: Before installing the cylinder head, be sure to also remove old gasket material from the engine block