GM Lumina/Silhouette/Transport APVs 1990-1999 Repair Guide

Rocker Arms/Shafts

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REMOVAL AND INSTALLATION



3.1L Engine

A very simple ball pivot-type rocker train is used. Motion is transmitted from the camshaft through the hydraulic lifter and push rod to the rocker arm. The rocker arm pivots on its ball and transmits the camshaft motion to the valve. The rocker arm ball locates on a stud, threaded into the head, and is retained by a nut. The push rod is located by a guide plate held under the rocker arm stud, assuring that the rocker arm operates in the plane of the valve.

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the rocker arm (valve) covers, as outlined in this section.
  4.  
  5. Unfasten the rocker arm bolts, then remove the rocker arms by lifting them straight out as an assembly.
  6.  
  7. Remove the pushrods.
  8.  

Make sure to keep all components in order for reassembly!

  1. Place rocker arms, bolts and pushrods in a rack so they can be reinstalled in the same locations from which they were removed. Inspect the rocker arms, and pushrods for abnormal/excessive wear, replace as necessary.
  2.  

To install:

Before installing the rocker arms, bolts, and pushrods, coat their bearing surface with a suitable prelube. Make sure to install these components in the exact locations from which they were removed.

  1. Install the pushrods, making sure they seat properly in the lifter.
  2.  
  3. Install the rocker arms and bolts.
  4.  
  5. With all the rocker arms attached and the lower ends of the pushrods in the lifter seats, bring #1 cylinder to TDC (Top Dead Center) compression stroke. The rotor would be pointing at the #1 spark plug wire in the distributor cap.
  6.  
  7. Adjust the intake valves on cylinders #1, #5, #6. Adjustment is 1 1 / 2 turns past zero lash.
  8.  
  9. Adjust the exhaust valves on cylinders #1, #2, #3. Adjustment is 1 1 / 2 turns past zero lash
  10.  
  11. Next, bring #4 cylinder to TDC (Top dead Center) compression stroke. The rotor would point to the #4 spark plug wire at the distributor cap.
  12.  
  13. Adjust the intake valves on cylinders #2, #3, #4. Adjustment is 1 1 / 2 turns past zero lash
  14.  
  15. Adjust the exhaust valves on cylinders #4, #5, #6. Adjustment is 1 1 / 2 turns past zero lash
  16.  
  17. Install the rocker arm (valve) cover(s), as outlined in this section.
  18.  
  19. Connect the negative battery cable.
  20.  

3.4L Engine

On these engine, a roller rocker type valve train is used. Motion is transmitted from the camshaft through the hydraulic roller lifter and pushrod to the roller rocker arm. The rocker arm pivots on needle roller bearings and transmits the camshaft motion to the valve. The rocker arm pedestal locates in a slot in the cylinder head and the rocker arm is retained in the cylinder head by a bolt. The pushrod is located by the rocker arm.

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the rocker arm (valve) covers as outlined in this section.
  4.  
  5. Unfasten the rocker arm bolts, then remove the rocker arms from the cylinder head.
  6.  
  7. Remove the pushrods, being careful that they do not fall down into the lifter valley. Note that the intake and exhaust pushrods are different lengths, with the exhaust pushrod being the longer of the two. The intake pushrods are 5.68 in. (144.18 mm) long and the exhaust pushrods are 6.0 in. (152.51 mm) long.
  8.  
  9. Place rocker arms, bolts and pushrods in a rack so they can be reinstalled in the same locations from which they were removed. Inspect the rocker arms, and pushrods for abnormal/excessive wear, replace as necessary.
  10.  

See Figure 1



Click image to see an enlarged view

Fig. Fig. 1: Exploded view of the rocker arms and pushrods

To install:

Before installing the rocker arms, bolts, and pushrods, coat their bearing surface with a suitable prelube. Make sure to install these components in the exact locations from which they were removed.

  1. Install the pushrods, making sure they seat properly in the lifter.
  2.  
  3. Install the rocker arms and bolts. Tighten the bolts to 89 inch lbs. (10 Nm), plus an additional 30° turn.
  4.  
  5. Install the rocker arm (valve) cover, as outlined in this section.
  6.  
  7. Connect the negative battery cable, then inspect for proper fluid levels and for oil leaks.
  8.  

3.8L Engine

The rocker arms for each bank of cylinders pivot on pedestals which are bolted to the cylinder head. Hydraulic roller valve lifters and tubular pushrods are used to operate the overhead rocker arms and valves of both banks of cylinders from a single camshaft. This system requires no lash adjustment at time of assembly or in service. The operation of hydraulic valve lifters is described below.

In addition to its normal function of a cam follower, each hydraulic valve lifter also serves as an automatic adjuster that maintains zero lash in the valve train under all operating conditions. By eliminating all lash in the valve train and providing a cushion of oil to absorb operating shocks, the hydraulic valve lifter promotes quiet valve operation. It also eliminates the need for periodic valve adjustment to compensate for wear of parts.

Each rocker arm and valve is supplied with oil through the tubular pushrod. This oil comes from the inside of the lifter, passing around the metering valve and through a hole in the lifter pushrod seat. Oil from the pushrod passes through a hole in the rocker arm pushrod seat, and emerges on top of the pushrod seat boss.

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the rocker arm (valve) covers, as outlined in this section.
  4.  
  5. Unfasten the rocker arm bolts, then remove the rocker arms by lifting them straight out as an assembly.
  6.  

See Figures 2 and 3

Click image to see an enlarged view

Fig. Fig. 2: Removing the rocker arm hold-down bolt



Click image to see an enlarged view

Fig. Fig. 3: Removing the rocker arm from the head

  1. Remove the pushrods.
  2.  

Make sure to keep all components in order for reassembly!

  1. Place rocker arms, bolts and pushrods in a rack so they can be reinstalled in the same locations from which they were removed. Inspect the rocker arms, and pushrods for abnormal/excessive wear, replace as necessary.
  2.  

See Figure 4

Click image to see an enlarged view

Fig. Fig. 4: Typical valve train components-3.8L engine

To install:

Before installing the rocker arms, bolts, and pushrods, coat their bearing surface with a suitable prelube. Make sure to install these components in the exact locations from which they were removed.

  1. Install the pushrods, making sure they seat properly in the lifter.
  2.  
  3. Install the rocker arm assemblies and secure with the retaining bolts. Tighten the bolts to 11 ft. lbs. (15 Nm), plus an additional 90° rotation.
  4.  
  5. Install the rocker arm (valve) cover, as outlined in this section.
  6.  
  7. Inspect for proper fluid levels and for oil leaks.
  8.  

 
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