Camshafts and Tappets

GENERAL INFORMATION

Camshaft Bearing Cap Bolt Tightening Sequence

Before installation, apply sealant to the shaded areas of the exhaust camshaft left bearing cap.

Removal

PROCEDURE

1. Remove the ignition distributor.

2. Remove the camshaft sprockets.

3. The front and rear camshaft bearing caps differ from the other bearing caps. On later-production vehicles, identification marks are cast into the top of the caps (for the exhaust camshaft E2, E5; for the intake camshaft I2, I5). On early-production vehicles, the bearing cap numbers may be absent, so before removal, make marks indicating the sequence number and orientation of each cap.

4. Loosen the camshaft bearing cap bolts in the reverse of the sequence shown in the diagram. Loosen the bolts in several steps, one turn per step. After the springs are fully released, the bolts can be removed completely. Remove the front and rear caps first, then the exhaust camshaft caps. Remove the intake camshaft caps last.

5. Remove the camshafts.

6. Place the tappets and adjusting shims in separate numbered containers.

Inspection

PROCEDURE

1. Inspect the bearing surfaces in the caps and in the cylinder head. Check for scoring and signs of deep wear. Check the camshaft lobes for metal flaking (bluish areas), deep wear, and chipping caused by wear.

2. Check the runout of the center camshaft journal. If runout exceeds the specification, replace the camshaft.

3. Using a micrometer, measure each camshaft lobe and compare with the specifications. If wear is excessive or the camshaft is damaged, replace the camshaft.

4. Check the camshaft journal oil clearance. This can be done by two methods: either by direct measurement or by using plastigage.

5. When measuring clearance by the direct method, install the camshaft bearing caps on the cylinder head in their original order and orientation. Tighten the cap bolts to the specified torque, in the sequence shown in the diagram.

6. Measure the inside diameter of the cap bearing surfaces and compare with the specifications. If the inside diameter of any cap exceeds the limit, replace the cylinder head. The clearance can be determined as the difference between the bearing bore diameter with the cap installed and the camshaft journal diameter.

7. When measuring clearance with plastigage, clean both camshafts and the journal bearing surfaces in the cylinder head and caps. Place the camshafts in the cylinder head.

8. Lay pieces of plastigage along the camshaft journal bearing surfaces, parallel to the shaft axis. Take measures to prevent the camshafts from rotating, install the camshafts, and tighten the caps (see below).

9. Loosen the cap bolts and carefully remove the caps, taking care not to rotate the camshafts.

10. Compare the widest width of the crushed plastigage on each journal with the scale on the plastigage envelope.

11. Compare the measurement with the specification. If the clearance exceeds the specification, measure the camshaft journal diameter with a micrometer. If the diameter is less than the minimum allowable, replace the camshaft and check the journal clearances again. If the clearance is still above specification, replace the cylinder head and the bearing caps.

12. Check the tappets and the inner surfaces of the cylinder head for signs of wear. If the necessary measuring instruments are available, wear can be assessed by the difference between the tappet diameter and the cylinder head bore. Compare the resulting clearance with the value given in subsection 3.1.1.

1. Replace worn parts as necessary.

Installation

PROCEDURE

1. Thoroughly lubricate the tappets and the tappet bores in the cylinder head. Carefully insert the tappets, maintaining their original order. When installing, insert the tappet into the bore without tilting it. Insert the adjusting shims into the tappets and make sure they are installed correctly, then thoroughly lubricate the camshaft journals and lobes.

2. Install the camshafts. The exhaust camshaft can be easily identified by the distributor drive splines on the left end.

3. Make sure the slot on the crankshaft pulley is aligned with the pointer on the front cover. Orient the camshafts so that the lobes of No. 1 cylinder point away from the corresponding valves. With the camshafts correctly positioned, the locating pin of the intake camshaft sprocket at its front should point to 9 o'clock (viewed from the right side of the engine), and the locating pin of the exhaust camshaft should be in the upright vertical position (12 o'clock).

4. Make sure the mating surfaces of the bearing caps and the cylinder head bearing seats are perfectly clean, with no scratches or oil on these surfaces. Apply a thin layer of sealant to the mating surfaces of the far-left bearing cap of the exhaust camshaft.

5. Install the bearing caps, aligning them with the marks made during removal (or existing marks).

6. Tighten the cap bolts in the sequence shown in the diagram. Tighten the bolts evenly, gradually increasing the load, turning each bolt one turn per pass, until the caps contact the cylinder head. Then tighten the bolts to the specified torque. Perform the tightening only in the specified order to ensure even and gradual application of the valve spring force to the bearing caps.

7. Install the camshaft sprockets.

Warning: If the cylinder head and camshafts have been overhauled, check the valve clearances on a cold engine before installing the cylinder head cover.

8. Install the distributor.

9. Check the valve clearances.