2. The camshaft bearing journals are measured with a micrometer to check the diameter and ovality. Compare the values obtained with the previously obtained values for the bores of the camshaft bearings. To measure, install all bearing caps and tighten to the correct Specifications effort. Measure individual bearing bores using an internal indicator as shown in the illustration below.
Measuring the bores of the camshaft bearings. Shown here for a carbureted engine.
3. Based on Specifications determine the state 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 necks should be measured at 90°to obtain the correct value.
4. Measure the height of the cams with a micrometer. To do this, set the cheeks of the micrometer between the tip and the back of the cam to get the maximum size (see illustration below). Compare result with data Specifications. Worn cams affect valve control, resulting in insufficient filling of the cylinders.
Measuring the height of the cams with an indicator.
5. Measure the camshaft runout by inserting the camshaft with two journals into the prisms and placing a dial indicator probe against the middle journal of the bearing as shown in the illustration below. Rotate the camshaft slowly and read the indicator. If the value at two revolutions is greater than 0.10 mm, the shaft must be replaced.
Check camshaft runout. Camshafts are not subject to straightening.
6. To check the axial play, insert it into the cylinder head and secure with 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 contact surface of the camshaft and the inside of the cover. If necessary, replace the corresponding part.
Checking the axial play of the camshafts. Shown for injection engine.
7. On a carbureted engine, measure the tappet diameter and cylinder head bore diameter. The difference between these values gives backlash. If it is too large, the pushrods or cylinder head must be replaced.