GM Cadillac 1967-1989 Repair Guide

Rocker Arms

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REMOVAL & INSTALLATION



The 6-252 and the 8-429 engines use a rocker arm shaft assembly. For these procedures refer to the Rocker Arm Shaft Assembly.

Except 8-250, 8-273, 8-307, 8-368 (MD), and 8-350 Diesel

See Figures 1, 2, 3 and 4

  1. Remove the valve cover.
  2.  
  3. Remove the rocker arm flanged bolts, and remove the rocker pivots.
  4.  
  5. Remove the rocker arms.
  6.  

Remove each set of rocker arms (one pair per cylinder) as a unit.

  1. To install, position a set of rocker arms (for one cylinder) in the proper location.
  2.  

Install the rocker arms for each cylinder only when the lifters are off the cam lobe and both valves are closed.

  1. Coat the replacement rocker arm and pivot with SAE 90 gear oil and install the pivots.
  2.  
  3. Install the flanged bolts and tighten alternately to specifications.
  4.  



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Fig. Fig. 1: Mark all pushrods before removal - keep rocker arms in order



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Fig. Fig. 2: Removing the rocker arm pivot - keep components in order



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Fig. Fig. 3: Removing the rocker arm



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Fig. Fig. 4: Removing the pushrods - keep pushrods in order

1981 and Later 8-368 (MD) Modulated Displacement Engine

See Figure 5

These engines feature a modulated displacement design that can operate eight, six or four cylinders depending on driving requirements. The selective operation of the number of cylinders is controlled by a microprocessor that operates four engine valve selector units. The selector units are electromechanical devices which can deactivate both the intake and the exhaust valve of a cylinder.

Because of the complexity of this system it is suggested that any service of the rocker arms be performed by an authorized Cadillac dealer.



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Fig. Fig. 5: Modulated displacement valve train details: on the left, the selector body is prevented from moving upward by contact between the projections on the body and the blocking plate above it, allowing normal valve operation. On the right, the solenoid has rotated the blocking plate, aligning the windows with the body projections. As the rocker arm rises, the fulcrum rides up the stud and lifts the body. The rocker pivots about the tip of the valve, which remains closed.

8-250, 8-273 Engine

See Figures 6 and 7

  1. Remove the valve cover.
  2.  
  3. Remove the five nuts from the stud-headed bolts, then remove the valve train support with the rocker arms and pivots attached as an assembly.
  4.  

This method is preferred as the pivot assemblies may be damaged if the pivot bolt torque is not removed evenly against the valve spring pressure.

  1. Place the support in a vise, then remove the rocker arms and pivots in pairs for each cylinder.
  2.  

To install:
  1. Position the rocker arms and pivots to the valve train support and loosely install the pivot bolts. Torque the pivot bolts to 20 ft. lbs. (27 Nm).
  2.  

When installing new parts, thoroughly lubricate all parts with SAE 90 gear oil.

  1. Position the valve train support with the rocker arms and pivots installed over the five stud headed head bolts.
  2.  
  3. Position the pushrod into the seat of each rocker arm and loosely install the five retaining nuts. Tighten the five nuts alternately and evenly while checking the positioning of the push rods. When the nuts are all the way down, tighten to 35 ft. lbs. (47 Nm).
  4.  
  5. Install the valve cover.
  6.  



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Fig. Fig. 6: Rocker arms and support - 1982-84 8-250 engine



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Fig. Fig. 7: Rocker arms and support - 1985-89 8-250 and 8-273 engines

8-307 Engine

See Figure 8

  1. Remove the valve covers.
  2.  
  3. Remove the rocker arm bolts.
  4.  
  5. Remove the pivot.
  6.  
  7. Remove the rocker arms.
  8.  

To install:
  1. Lubricate the wear points with engine oil.
  2.  
  3. Install the pivot and rocker arms and tighten the bolts to 22 ft. lbs. (30 Nm).
  4.  
  5. Install the valve covers.
  6.  



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Fig. Fig. 8: Disassembled view of the rocker arm and springs - 8-307 engine

Diesel Engine

See Figure 9

When the diesel engine rocker arms are removed or loosened, the lifters must be bled down to prevent oil pressure buildup inside each lifter, which could cause it to raise up higher than normal and bring the valves within striking distance of the pistons.

  1. Remove the valve cover.
  2.  
  3. Remove the rocker arm pivot bolts, the bridged pivot and rocker arms.
  4.  
  5. Remove each rocker set as a unit.
  6.  
  7. To install, lubricate the pivot wear points and position each set of rocker arms in its proper location. Do not tighten the pivot bolts for fear of bending the valves when the engine is turned.
  8.  

DIESEL ENGINE BLEED-DOWN
  1. Before installing any removed rocker arms, rotate the crankshaft so that No. 1 cylinder is 32 degrees BTDC. This is 50mm (2 in.) counterclockwise from the 0 pointer on the timing indicator on the front of the engine. If only the right valve cover was removed, remove the glow plug from No. 1 cylinder to determine if the piston is in the correct position. If the left valve cover was removed, rotate the crankshaft until the No. 5 cylinder intake valve pushrod ball is 7mm (0.275 in.) above the No. 5 cylinder exhaust valve pushrod ball.
  2.  


WARNING
In order to avoid pushrod damage, use only hand wrenches to torque the rocker arm pivot bolts.

  1. If the No. 5 cylinder pivot and rocker arms were removed, install them. Torque the bolts alternately between the intake and exhaust valves until the intake valve begins to open, then stop.
  2.  
  3. Install the remaining rocker arms except No. 3 and No. 8 intake valves, if these rockers were removed.
  4.  
  5. If removed, install but do not torque the No. 3 valve pivots beyond the point that the valve would be fully open. This is indicated by a strong resistance while still turning the pivot retaining bolts. Going beyond this will bend the pushrod. Torque the bolts slowly, allowing the lifter to bleed down.
  6.  
  7. Finish torquing the No. 5 cylinder rocker arm pivot bolt slowly. Do not go beyond the point that the valve would be fully open. This is indicated by a strong resistance while still turning the pivot retaining bolts. Going beyond this will bend the pushrod.
  8.  
  9. DO NOT turn the engine crankshaft for at least 45 minutes, allowing the lifters to bleed down. This is important.
  10.  
  11. Finish reassembling the engine as the lifters are being bled.
  12.  



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Fig. Fig. 9: Removing rocker arms - 8-350 diesel engine

 
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