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Revised cylinder head installation procedure for 1997-2002 GM 5.7L VIN G engines

Engine Builders: The AERA Technical Committee offers the following information on a revised cylinder head installation procedure for 1997-2002 GM 5.7L VIN G engines, Figure 1. This revised procedure should be used any time the cylinder heads are being installed and supersedes information found in earlier published service manuals. Previously published technical bulletin TB 1624 should be discarded because the information contained here is the most current.

Previously, it was acceptable to reuse the 8 mm head bolts. It is now recommended that all cylinder head bolts be replaced at the time of cylinder head installation. New 11 mm bolts come with a pre-applied sealer and lubricant and no other sealant should be used on them.

1. Tighten new 11 mm bolts (1-10) in sequence to 22 ft.lbs. (30 Nm).
2. Rotate those bolts (1-10) in sequence an additional 90° turn using a torque angle meter.
3. Rotate only bolts 1-8 in sequence an additional 90° turn using a torque angle meter.
4. Rotate remaining 11 mm bolts 9 and 10 in sequence an additional 50° turn using a torque angle meter.
5. Apply a .200˝ (5 mm) bead of locking compound (GM p/n 12345382 or equivalent) to the new 8 mm bolt threads, and tighten bolts (11-15) in sequence to 22 ft.lbs. (30 Nm).

AERA is not aware of an aftermarket source for these bolts.

Note: Do not reuse either the 8 mm or 11 mm head bolts.

Engine Builders: The AERA Technical Committee offers the following information regarding a connecting rod fastener caution on Allis Chalmers 844 cubic inch (13.8L) diesel engines. These engines have used six different connecting rod bolt designs during 20 years of production (1970-1990). The type of connecting rod bolts use one of four torque values. If the incorrect torque value is used, engine failure may occur.

When installing the piston and connecting rod assemblies, clean and dry the connecting rod bolt or capscrew threads. Lubricate the bolt threads with clean SAE W 30 engine oil. Figure 2 (above) illustrates the difference in the connecting rod fasteners and the appropriate torque specifications.

Engine Builders: The AERA Technical Committee offers the following information regarding 1996-2001 Subaru 2.5L VIN 6 engine cylinder head installation, the result of a service manual update by Subaru. Previously published information has been modified to help seal the cylinder head gasket.

1. Apply engine oil to washers and bolt threads.
2. Tighten all bolts to 29 Nm (3.0 kg-m, 22 ft.lbs.) in the alphabetical sequence shown at right (Figure 3).
3. Then, tighten all bolts to 69 Nm (7.0 kg-m, 51 ft.lbs.) in alphabetical sequence.
4. Back off all bolts 180° first; and then back them off 180° again.
5. Tighten bolts (A) and (B) to 34 Nm (3.5 kg-m, 25 ft.lbs.)
6. Tighten bolts (C), (D), (E) and (F) to 15 Nm (1.5 kg-m, 11 ft.lbs.).
7. Tighten all bolts another 80-90° in alphabetical sequence. CAUTION: Do not tighten bolts more than 90°.
8. Finally, tighten all bolts another 80°-90° in alphabetical sequence.
9. CAUTION: The total "retightening angle" (in steps 7 and 8) should not exceed a total of 180° rotation.

Engine Builders: Originally, 1993-’99 Mazda 2.5L KL V6 engines were manufactured with pistons with different valve cutouts. OEM and aftermarket pistons have been revised to allow use of a single design on either bank.

The previously used piston "L" (left) and "R" (right) marks have been replaced with an "F" mark, which must face toward the front of the engine. If the piston is installed facing the wrong direction, a knocking noise and possible engine damage may result, as the pistons are offset .040˝ (1.016 mm).

Mazda also recommends replacing only in sets when installing the revised pistons.