The Complete Guide: FAW Cylinder Head Assembly2 Components for the CA4251P66K24T1A3E5 Tractor

Welcome to our complete guide for the FAW Cylinder Head Assembly2 components, a continuation of our in-depth analysis of the powertrain for the FAW Jiefang CA4251P66K24T1A3E5 6×4 diesel semi-trailer tractor.

While our previous guide detailed the bare cylinder head casting, this FAW Cylinder Head Assembly2 guide focuses on the critical ancillary and assembly components. This includes the single most important seal in the engine—the head gasket—as well as the high-tensile head bolts, camshaft bearings, and all the covers and gaskets required to complete the top-end assembly.

This technical resource is designed for professional engine technicians, machine shops, and parts managers. We will deconstruct this system into its smallest serviceable units, providing the precision and detail necessary for a reliable, leak-free, and powerful engine rebuild.

The Critical Seal: Cylinder Head Gasket Assembly (1003020-81D)

The parts list begins with the ‘Cylinder Head Assembly’ (1003010-81D), which refers to the main component from our previous guide, but the first *new* item here is the ‘Cylinder Head Gasket Assembly’ (1003020-81D). This is, without question, the single most critical seal in the entire engine and a core part of the FAW Cylinder Head Assembly2 system.

This is not a simple paper gasket. This assembly is a Multi-Layer Steel (MLS) gasket, composed of multiple thin layers of high-grade, spring-steel sheets. These layers are coated with special elastomer (rubber) compounds that are precisely applied to seal specific passages. The steel layers provide the structural strength to contain combustion pressures that can exceed 2,500 PSI, while the elastomer layers “cold seal” the much lower-pressure coolant and oil passages.

The MLS gasket’s design is a precise map of the head and block. It has “stopper” layers to increase clamping pressure around the cylinders and specialized “beads” to seal off the water jackets and oil galleries, preventing the three fluids (oil, coolant, and combustion gas) from ever mixing. This gasket is a single-use item. Once it has been compressed by the head bolts, its internal structure is permanently deformed and it must never be re-used.

Clamping Force: The Cylinder Head Bolts (1003047-53D)

A gasket can only seal if it is held under immense and perfectly uniform pressure. This is the job of the 26 ‘Cylinder Head Bolts’ (1003047-53D). These are the most specialized and critical fasteners in the entire FAW Cylinder Head Assembly2 system.

These are **Torque-to-Yield (TTY)** bolts, also known as “stretch” bolts. Their design is a feat of material science. Unlike a normal bolt which is tightened to a specific torque and acts like a stiff spring, a TTY bolt is designed to be tightened *past* its elastic limit and into its “plastic” deformation zone.

The installation procedure is a precise, multi-stage process. First, all 26 bolts are “snugged down” in a specific spiral sequence to a low, initial torque (e.g., 50 N·m). This evenly seats the gasket. Second, they are tightened again in the same sequence to a higher torque (e.g., 100 N·m). Finally, they are tightened one or more times by a specific *angle* (e.g., +90 degrees, then another +90 degrees), using a torque-angle gauge.

This final “angle” turn is what stretches the bolt. Once stretched, the bolt acts like a very long, very strong spring, providing a perfectly consistent clamping force across the entire head, regardless of minor variations in thread friction. This force is essential to prevent the head from “lifting” during the combustion stroke, which would instantly cause the head gasket to fail.

Because these bolts have been *permanently* stretched, they are **single-use only**. Re-using a TTY bolt is a catastrophic, amateur mistake. It will not stretch a second time and will not provide the correct clamping force, guaranteeing a head gasket failure. Any professional service on the FAW Cylinder Head Assembly2 requires a new set of 26 bolts.

Camshaft Bearing Shells (1003072-81D / 1003073-81D)

While the previous guide showed the camshaft *caps*, this FAW Cylinder Head Assembly2 parts list details the bearing surfaces themselves. The parts list calls for seven ‘Camshaft Upper Bearing Shells’ (1003072-81D) and seven ‘Camshaft Lower Bearing Shells’ (1003073-81D).

These are the “half-shells” that form the complete bearing journal for the camshaft. The “lower” shells (1003073-81D) are placed in the “saddles” of the cylinder head casting, while the “upper” shells (1003072-81D) are placed in the removable camshaft caps. When assembled, they create a perfect circle.

These are not simple pieces of metal. They are precision, multi-layer components, typically a steel backing for strength, with a very thin layer of soft bearing material (like a bronze-aluminum-tin alloy) on the surface. The camshaft does not ride *on* this metal; it rides on a microscopic film of oil (hydrodynamic lubrication) that is pumped in through a small hole in the bearing shell. The soft material is there to absorb tiny particles and to prevent catastrophic damage if oil pressure is momentarily lost.

Covers, Gaskets, and Ancillaries

This FAW Cylinder Head Assembly2 list includes all the external covers. The ‘Gear Chamber Cover Plate’ (1003051-81D) and its ‘Gasket’ (1003052-81D) seal the front of the head, protecting the camshaft timing gears.

The ‘Camshaft Gear Sensor Cover Plate Assembly’ (1003090-81D) is a critical component. This cover is precisely located to hold the camshaft position sensor, which tells the engine’s ECU the exact position of the camshaft for timing fuel injection and ignition.

Similarly, the ‘Intake Manifold Cover Plate’ (1008018-81D) and its ‘Gasket’ (1008019-81D) are used to seal an access port on the intake side. The list also details minor but crucial seals like the ‘Cylinder Head Sealing Half-moon’ (1003042-81D), a rubber plug that seals the semi-circular hole left from machining the camshaft saddles, and the ‘Front Lifting Lug’ (1003058-81D), which is bolted on to allow a crane to safely lift the heavy assembly.

FAW Cylinder Head Assembly2 Parts List

The following table provides the complete, detailed breakdown of all components identified in the ‘Cylinder Head Components’ diagram for the FAW CA4251P66K24T1A3E5 tractor.

Technical Specifications and Assembly Context

The specifications for the FAW Cylinder Head Assembly2 system are defined by its role in sealing and completing the engine’s top end.