2. The camshaft bearing journals are measured with a micrometer to check the diameter and out-of-roundness. The obtained values are compared with the previously obtained values of the camshaft bearing bores. To measure, install all bearing caps and tighten to the appropriate Specifications force. Measure the individual bearing bores with an internal indicator as shown in the illustration below.
Measuring camshaft bearing bores. Shown here for a carbureted engine.
3. Based on Specifications determine the condition of the parts. To accurately determine the diameter of the bearing journals, the camshaft is placed on two prisms, as shown in the illustration below.
Measuring the diameter of the camshaft bearing journals. All journals should be measured at an angle of 90° to obtain the correct value.
4. Measure the cam height with a micrometer. To do this, place the cheeks of the micrometer between the tip and the back of the cam to obtain the maximum dimension (see illustration below). Compare the result with the data Specifications. Worn cams affect valve control, resulting in insufficient cylinder filling.
Measuring the height of the cams using an indicator.
5. Measure the camshaft runout by placing the camshaft with both journals in the prisms and applying the feeler gauge to the middle journal of the bearing as shown in the illustration below. Slowly rotate the camshaft and read the dial indicator readings. If the value after two revolutions is greater than 0.10 mm, the shaft should be replaced.
Check the camshaft runout. Camshafts cannot be straightened.
6. To check the axial clearance, insert it into the cylinder head and secure it with the bearing caps. Install a dial indicator on the end of the shaft and move the shaft from side to side as shown in the illustration below. If the value is more than 0.20 mm, check the mating surface of the camshaft and the inner side of the cap. Replace the corresponding part if necessary.
Checking the axial play of the camshafts. Shown for an injection engine.
(The source of the article is on the website: «NissanBook.ru»)
7. On a carburetor engine, measure the tappet diameter and the bore diameter in the cylinder head. The difference between these values gives the clearance. If it is too large, the tappets or cylinder head must be replaced.