ENGINE AR-PRIMARY 3801769 - Caterpillar

Spacer Plates
The former aluminum spacer plates (standard thickness) have been replaced by the new steel spacer plates. The new plates provides added durability and reusability when compared to the former plates. The new plates are functionally interchangeable with the former plates. A wider selection of cleaning methods can be used with the steel plates than with the aluminum plates to simplify repair. In addition, new steel spacer plates are available for parts service. The spcer plates are 0.076 mm (0.003 in) thinner than the productions spacer plates. They can compensate for repairs that produce liner projection less than 0.076 mm (0.003 in). They can be used when liner projection across all the cylinder bank is consistent but near the minimum specification of 0.152 mm (0.001 in). If inspection of the block top deck reveals no measurable damage directly under the liner flanges, but the average liner projection is less than 0.076 mm (0.003 in), these new service spacer plates can be installed. Note: The use of the service spacer plate is situations that result in excessive liner projection [greater than 0.152 mm (0.006 in)] is not an acceptable repair.
See the "Spacer Plate" Chart for model usage and part numbers. See the "Effectivity Of Cylinder Head Joint Improvements" Chart for effective serial numbers.
Head Bolts (3406 only)
New 12 point head bolts are used to secure the head to block joint. The new 9X8904 Bolts (which require a 3/4inch, 12 point socket) are now used in place of the former 2H3750 Standard Hex Head Bolts (which require a 11/8inch 6 or 12 point socket). The rocker arm support bolts/studs remain unchanged. The new bolts provide better reusability due to an improvement in yield strength over the former bolt. The 9X8904 Bolt MUST be used in the 3406E (5EK) Truck Engine. In the 3406A, 3406B, and 3406C engines, the two bolts are functionally interchangeable and can be mixed within the same engine.
Prior to final assembly, lubricate all the head bolt threads, washers and bottom of bolt heads with a thin coat of 6V4876 Molykote Paste. Use of this friction reducing paste will significantly improve the load on the gasket. See the chart for effective serial numbers.
Spacer Plate Gasket (3406 only)
The new 6I4024 Spacer Plate Gasket replaces the former 7C3037 Gasket. The new gasket has a profile that matches the bottom of the cylinder head for improved fluid sealing ability. The new gasket retains the latex coating on the surface adjacent to the cylinder block. See the chart for effective serial numbers.
Improved Water Flow (Cylinder Heads)
Changes have been made to the Cylinder Heads to provide improved water flow reducing the possibility of hot spots in the heads. See the chart for effective serial numbers.
Liner Projection
The liner projection specifications have not changed. See the appropriate Specifications Module.
The preferred method of obtaining liner projection measurements follows. See illustration. After assembly of cylinder liners (7), spacer plate gasket (5), and spacer plate (4) to cylinder block (6), secure both the plate and liners with the hardware