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GMC 1000 Series Engine Information

The following technical bulletins were published by AERA.


                          Cylinder Head Installation Procedure For
                              Perkins 1000 Series Diesel Engines

The AERA Technical Committee offers the following information regarding cylinder head installation procedures for Perkins 1000 Series diesel engines. The following applies for all L4 and L6 cylinder Series 1000 engines. 

Before installing the gasket on the block, check to make sure head and block surfaces are clean, dry, and free of nicks and scratches. 

Note: Certain engines have two location pins (See Figure 1) one at each end of the cylinder head, pressed in the cylinder block to hold the head gasket in the correct position as the cylinder head is installed. To avoid damage to the cylinder head gasket, ensure that the location pins are pressed in the cylinder block before installing the head. The head gasket must be installed dry. DO NOT USE SEALER and follow the steps listed below

1. Install head gasket with stamped FRONT TOP. See Figure 1 below.
2. To ensure the cylinder head is fitted into the correct position, fit two suitable ?  UNF guide studs in positions 15 and 20. Then, place the cylinder head in position on the block.
3. Lightly lubricate the threads and thrust face of all cylinder head bolts. Start some of the head bolts, remove guide studs and install remaining bolts. 
4. In several passes, tighten all bolts in sequence to 80-ft/bs (110 Nm) as shown in Figure 2 or 3.
5. Repeat step #4 to make sure that all the bolts are torqued to 80 ft/lbs.
6. The final step is a torque to angle (TTY) for each head bolt. There are three different head bolt lengths, which require different amounts of rotation. Using an angle gauge attached to the socket and rotate bolts as follows.

Rotate in sequence bolts marked S 150°, See Figure 2 or 3.
Rotate in sequence bolts marked M 180°, See Figure 2 or 3.
Rotate in sequence bolts marked L  210°, See Figure 2 or 3.

                                                              The AERA Technical Committee


                                              New Rear Oil Seal Assemblies For 
                           Perkins 4.0L and 4.1L New & Old 1000 Series & 4.41 Engines

The AERA Technical Committee offers the following information regarding a new rear oil seal assembly?s for Perkins 4.0L and 4.1L new and old 1000 series & 4.41 engines.

Beginning in May 2001, all production engines are fitted with a new type of rear oil seal assembly. In accordance with this, the designs of the cylinder block and the bridge gap piece have changed to accommodate the revised seal.
There are two types of new rear oil seal assemblies: Part #2418F701 and Part #2418F703 (dust cover version)

The new rear oil seal has been introduced from the beginning with the following engine numbers:
A*****U993671H 	1000 Series 4 cylinder engines.
A*****U176357H	New 1000 Series 4 cylinder engines.
Y*****U764752H	1000 Series and New 1000 Series 6 cylinder engines.
LM*****U920938H	4.41

Caution: Engines built before the numbers shown above must be fitted with the old type of seal, Part numbers 414V066 or U4142V067 as shown in the relevant workshop manual.

Note: This new rear seal is manufactured as a one-piece assembly and can only be fitted in one position.

If the crankshaft seal surface has a wear-groove caused by the oil seal, fit a wear- sleeve part number 21826222 (fitting instructions supplied with the repair kit) to the crankshaft flange.

An alignment tool for the rear oil seal assembly is currently not available from Perkins. Perkins has therefore provided the information in Figure 1 to allow fabrication of the required tool.
Figure 1
1. Outer surface (1) to be coarse knurled.
2. All sharp edges to be removed.
3. All dimensions in Millimeters.
4. To be made from material EN 32 and hardened to a .05mm depth.

                                                          THE AERA TECHNICAL COMMITTEE


                                         Detroit Diesel Allison 71 Series
                                Cylinder Liner Compression Ring Gaskets

GMC has changed their specifications for the 71 series diesel engine cylinder liner compression ring gaskets.  Their tolerance specifications are such that when replacing these gaskets they must be replaced in matched sets.

The compression ring gaskets are color-coded on the top surface with a 3/4 black, white or orange stripe.  Each color represents the following compressed thicknesses:

                    Black stripe        .059 - .063
                    Orange stripe     .058 - .062
                    White stripe        .057 - .061

Mixing the colors of rings under any one cylinder may cause engine damage.

                                                                             The AERA Technical Committee


                                   Cylinder Head Resurfacing Caution On
                                  GM (GMC) 5.7L (350 CID) Diesel Engines

General Motor Corporation warned that it is not to possible to resurface the cylinder head on the 5.7L (350 CID) diesel engine due to the extremely tight clearance between the valves and the head of the piston. The prechamber must be recessed into the cylinder head by more than .005 or must not protrude out of the head by more than .003.

Note: GMC states that a cylinder head must be replaced if it is warped more than .010.

Before the cylinder head is reinstalled, make sure that the mounting bolt holes are tapped deep enough in the block and threads are not damaged. Blow out any chips or liquid and lightly oil the bolt threads in the block. Screw the bolt into the block by hand to a depth that is less than the cylinder head thickness.

Bolts that are rusty should be cleaned by wire brushing the threads. Before installing, lubricate the threads and underneath the head of the engine bolt with engine oil. Torque to 130 ft.lbs. (176Nm) in the sequence shown below:

                                                                                 The AERA Technical Committee


                                      New Cylinder Liner O-Ring Seals On
                                      Cummins NH/NT 6 Cylinder Engines

Cummins Engine Company has released new O-ring seals for the cylinder liners in NH/NT 6 cylinder engines.  The new seals are made of an EP material and have a smaller diameter cross-section.

The new seal replaces both the old center seal #3008998 and the old lower seal #183049.  The new seal carries Cummins part #3032874 and is black in color with one blue dot.

The new O-ring seals are not to be intermixed with the former seals on the same liner.  Cylinder liner deformation will result.  You can use the former seals and new seals in the same engine as long as they are used in the correct combinations on each liner.  The illustration below shows the correct combinations.

                                                                       The AERA Technical Committee


                                               Oil in Cooling System on
                                         VW 1.5L & 1.6L Diesel Engines

AERA members have reported instances of engine oil in the cooling system on VW 1.5L diesel engines.  According to AERA sources, the problem is related to a crack in the cylinder head bolt hole located near the oil gallery feeding the cylinder head.

The oil feed gallery in the block is located on one side of the center head bolt hole and a coolant jacket is on the opposite side of the bolt hole.  Pressurized engine oil is diverted through a slot in the head gasket and is feed up the side of the head bolt to the cylinder head.  The oil also follows the bolt back down to the bottom of the bolt hole.  Should the crack in the head bolt hole extend to the coolant jacket, oil can mix with engine coolant.

This problem is generally found on engines equipped with 11mm head bolt holes.  Later design engines utilize 12mm head bolts and do not exhibit this defect.  At the time of this writing no successful repair procedure is available.

                                                                       The AERA Technical Committee


                                        Cylinder Head Specifications on
                                              Case 207 Diesel Engines

The following cylinder head specifications should be considered when remanufacturing Case Model 207 diesel engine cylinder heads.

The minimum cylinder head thickness has been established at 3.968 with a new head measuring 4.000 +/- .005.  Heads are measured from the deck surface to the rocker cover rail.

Valve recession should be checked and adjusted if necessary to a maximum recession of .015, below the deck surface, for both intake and exhaust valves.  Valves on new cylinder heads are generally flush with a +/- .005 tolerance.

                                                                       The AERA Technical Committee

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