Usage:
All 3400 Machine Engines
- SUPPLEMENT: 09/05/94
Service Magazine; July 4, 1994; Page 11; "New Cylinder Head Gasket, Spacer Plate And Head Bolts Used; New Cylinder Liner Projection Measurement Method; New Cylinder Head Torque Sequence; Improved Coolant Flow (Cylinder Heads)".
In the "SPACER PLATE SPECIFICATIONS" chart, in the "Serviceable Part No." column, the part number 6I1389 is NOT correct. The spacer plate part number is 6I3189.
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Head Gasket (3406 only)
The former 7E6000 Cylinder Head Gasket has been replaced by the new 6I3066 Cylinder Head Gasket. This new gasket features a graphite body for added heat resistance. The body material will resist extrusion and provide better oil sealing capability. It can withstand occasional exhaust gas seepage past the fire ring better than the previous material. This body design results in a more flexible gasket that requires extra care in handling and storage.
Gasket body performance is maximized when assembled with clean, dry components. It is important to thoroughly clean the cylinder head bottom deck, liner flanges, and spacer plate with component cleaner or alcohol prior to gasket installation.
The fire ring material has changed from mild steel to stainless steel to provide improved combustion sealing. The wrap material remains stainless steel and retains its tab style retention method to the body material. One benefit of the new gasket design is a decrease in sensitivity to liner projection that is low in the specified range. Another benefit is the stainless steel fire ring in the 6I3066 Gasket is less prone to deformation through thermal cycling than the previous head gasket. More load is retained on the fire ring, thus reducing exhaust gas leakage. The retorquing of cylinder head bolts DOES NOT improve the performance of this gasket. See the chart for effective serial numbers.
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The former aluminum spacer plates (standard thickness) have been replaced by the new steel spacer plates.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 shown in Illustration 1. The use of this hardware allows both the liner flange and spacer plate to be secured simultaneously without damaging the aluminum spacer plate. Use six 7H3598 Bolts (1), 8F1484 Washers (2) and 7K1977 Fiber Washers (3) per cylinder for consistent clamping load (see Liner Projection Hardware Usage Chart). This method alleviates the need for the "H" bar to hold down liners during projection measurements. Tighten bolts (1) evenly in four steps up to a maximum of 95 N·m (70 lb ft). Use the 8T0455 Liner Projection Tool Group to obtain four measurements on each liner flange.
Illustration 1. Location of components for liner projection measurement.
In some cases, the latex bead on the bottom of the spacer plate gasket may not fully compress and could affect readings on the exhaust manifold side and ends of the spacer plate. Measurements can be taken elsewhere on the liner flange to minimize this effect.
The allowable range for the entire set of liners 0.03 to 0.15 mm (.001 to .006 in), the maximum differential between high and low measurements made at four places around each liner is 0.05 mm (.002 in). The average projection of liners next to each other must not be more than 0.05 mm (.002 in). The maximum difference of all average measurements of all liners must not exceed 0.10 mm (.004 in).
New Cylinder Head Bolt Tightening Procedure (3406, 3408, 3412)
This new procedure includes both a new bolt tightening sequence and new torque values. These changes will provide the optimum and most uniform bolt load on the head to block joint. The following bolt tightening sequence and torque valves provide the most uniform bolt loading. This new procedure should be used instead of the procedure found in the service manuals.
3406/3412
Illustration 2. Cylinder Head Bolt Identification of 3406 and 3412. Large (3/4inch) head bolts or compression brake studs (on 3406) (1). Small (3/8inch) head bolts (2).
Put 6V4876 Molykote Paste on the large (3/4inch) bolt (1) threads and between the washer and the underside of the bolt heads. Tighten the bolts in the following step sequence:
1. Tighten bolts 1 through 14 in number sequence to 270 ± 25 N·m (200 ± 20 lb ft).
2. Tighten bolts 1 through 14 in number sequence to 470 ± 20 N·m (345 ± 15 lb ft).
3. Tighten bolts 1 through 14 in number sequence again to 470 ± 20 N·m (345 ± 15 lb ft).
4. Install the rocker arm shafts for the engine valves and the remaining (3/4inch) bolts or compression brake studs.
5. Tighten bolts 15 through 26 in number sequence to 270 ± 25 N·m (200 ± 20 lb ft).
6. Tighten bolts 15 through 26 in number sequence to 450 ± 20 N·m (330 ± 15 lb ft).
7. Tighten bolts 15 through 26 in number sequence again to 450 ± 20 N·m (330 ± 15 lb ft).
8. Tighten the twelve small (3/8inch) bolts (2) to 45 ± 7 N·m (33 ± 5 lb ft).
3408
Illustration 3. Cylinder Head Bolt Identification of 3408. Large (3/4inch) head bolts (1). Small (3/8inch) head bolts (2).
Put 6V4876 Molycoat Paste on the large (3/4inch) bolt (1) threads and between washer and under side of bolt heads. Tighten the bolts in the following step sequence:
1. Tighten bolts 1 through 10 in number sequence to 270 ± 25 N·m (200 ± 20 lb ft).
2. Tighten bolts 1 through 10 in number sequence to 470 ± 20 N·m (345 ± 15 lb ft).
3. Tighten bolts 1 through 10 in number sequence again to 470 ± 20 N·m (345 ± 15 lb ft).
4. Install the rocker arm shafts for the engine valves and the remaining (3/4inch) bolts.
5. Tighten bolts from 11 through 18 in number sequence to 270 ± 25 N·m (200 ± 20 lb ft).
6. Tighten bolts from 11 through 18 in number sequence to 450 ± 20 N·m (330 ± 15 lb ft).
7. Tighten bolts from 11 through 18 in number sequence to 450 ± 20 N·m (330 ± 15 lb ft).
8. Tighten the nine small (3/8inch) bolts (2) to 45 ± 7 N·m (33 ± 5 lb ft).