1. Check bearing surfaces for camshaft installation for cavities, scratches, scuffs and other signs of excessive wear. If defects are found, the head must be replaced.
2. Measure the outer diameter of each of the bearing journals of the shafts. Record the measurements and compare them with the nominal values given in the Specifications. Measure the inner diameters of the bearings in the cylinder heads and subtract from the results of the last measurements the results of the corresponding first ones. The resulting difference will be the size of the gaps in the shaft bearings. Compare the received data with the requirements of the Specifications. If necessary, replace shafts and/or heads.
3. Estimate the amount of radial runout on the shafts by laying them in V-blocks and using a plunger-type dial gauge. Rotate the shaft slowly in the blocks, record the readings taken and compare them with the nominal values (see specs). If necessary, replace the corresponding shaft.
4. Using a micrometer, measure the height of the cams of the shafts. Compare the measurement results with the requirements of the Specifications, then subtract them from the latter in order to determine the degree of wear of the cams. If the wear exceeds the limit value (see specs), replace the corresponding shaft.
5. Assess the condition of the working surfaces of the valve lifters.
Note. If the tappet contact surface is worn, it makes sense to also evaluate the condition of the corresponding camshaft cam/shim lob on DOHC engines.
On SOHC engines, the tappets must be held vertically to prevent air from entering them (see part SOHC engines this chapter).
6. Using a micrometer, measure the outer diameter of each pusher. Compare the measurement results with the requirements of the Specifications. The pushers worn out over an admissible limit replace.
7. Measure the diameter of each pusher, compare the results of measurements with the requirements of the Specifications. Replace guide assembly if necessary (SOHC engines), or cylinder head (DOHC engines).
8. Subtract the outside diameters of the tappets from the inside diameters of the respective slots in the guide/head to determine the clearance of the tappets in the slots - when installing new components (pushers, guide/head) the possibility of this parameter going beyond the permissible values is not excluded.
9. On SOHC engines, evaluate the wear of the rocker arms and their axles (see part SOHC engines this chapter). If the linings are excessively worn, the rocker arms must be replaced - in no case attempt to carry out their recovery wear.
10. Remember that the condition of all components, whether new or refurbished old, must be checked without fail before installation.