Toyota Cressida/Corona/Crown/MarkII 1970-1982 Repair Guide

Rocker Arms

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REMOVAL AND INSTALLATION





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Fig. Fig. 1 When assembling the rocker arms on the shaft, make sure they are in order-4M engine shown



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Fig. Fig. 2 Rocker shaft bolt removal sequence-8R-C and 18R-C engines



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Fig. Fig. 3 Rocker shaft bolt tightening sequence-8R-C and 18R-C engines

  1. Remove the rocker shaft assemblies, as detailed in the Cylinder Head portion of this section.
  2.  
  3. On the single rocker shaft engines (8R-C and 18R), remove the rocker shaft support attaching bolts (#2 in illustration) and the rocker shaft retaining screw (#3 in illustration). Slide the tension springs, rocker arms and supports off of the shafts.
  4.  

Make sure you keep the parts in order as they were removed from the shaft-this is very important.

  1. On the double rocker shaft engines, remove the rocker shaft assemblies. Remove the three retaining screws and slide the rocker supports, springs and rocker arms off of the shafts. Keep all parts in order;
  2.  

The shafts must be reassembled in the correct order.

  1. Assembly is in the opposite order of removal; make sure all components are reassembled in their original positions. Adjust the valves.
  2.  
  3. Check the oil level and top off if necessary.
  4.  

INSPECTION





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Fig. Fig. 4 Check the rocker arm shaft wear by wiggling the arm laterally on the shaft



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Fig. Fig. 5 Using a micrometer, measure the shaft diameter, then check the rocker arm inner diameter; the difference is the oil clearance

The oil clearance between the rocker arm and shaft is measured in two steps. Measure the outside diameter of the rocker shaft with a micrometer. Measure the inside diameter of the rocker arms with a dial indicator. The difference between the rocker arm inner diameter and the shaft outer diameter is the oil clearance. Clearance specs are as follows:



8R-C-0.0012-0.015 in. (0.030-0.381mm)
 
18R-0.00067-0.00201 in. (0.017-0.051mm)
 
20R-0.0004-0.0020 in. (0.010-0.050mm)
 
22R-0.0031 in. (0.078mm)
 
4M, 4M-E and 5M-E-0.0005-0.0013 in. (0.0127-0.0330mm)
 

If specs are not within these ranges, replace either the rocker shaft or rocker arm. Clearance can also be checked by moving the rocker arm laterally on the shaft when assembled. There should be little or no movement.

While disassembled, check the cam follower end (the flat end that contacts the camshaft) of the rocker arm for excess wear. The surface should be smooth and shiny. If excess wear is evident, check also the lobe of the camshaft, it may also be worn.

Reassemble the rocker shaft assemblies in the exact opposite order or removal. Accelerated camshaft wear and/or sloppy valve action will result if rocker arms are mixed and end up operating against the wrong cam lobes.

 
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