Checking the camshaft lift
1. The degree of wear of the camshaft lobes is checked by the cam lift value before removing the camshaft. Remove the head and cylinder covers.
2. Set the piston of the 1st cylinder to TDC of the compression stroke.
3. The check starts with the cams of the 1st cylinder. Loosen the rocker arm nuts and turn to the side. Set the dial indicator so that the indicator leg runs parallel to the rod axis and rests against the end of the rod (see photo).
4. Set the indicator to zero, turn the crankshaft in the direction of normal rotation. Immediately after the indicator arrow deflects in the opposite direction (the reading will start to decrease), read the reading, which is equal to the cam lift.
5. Set the piston of the 1st cylinder back to TDC of the compression stroke.
6. Move the dial indicator to the other push rod of the 1st cylinder and repeat the check.
7. Repeat the check for the valves of the remaining cylinders. Since each piston must be at TDC of the compression stroke, set the cylinders one by one, in the order of engine operation.
8. Compare the results with the standard. If the reduction in cam size due to wear exceeds the standard, replace the camshaft.
9. Remove the intake manifold, rocker arms, pushrods, camshaft sprocket and timing chain. Remove the radiator.
Warning! If the vehicle is equipped with an air conditioning system, it may be necessary to remove the air conditioning condenser. If the condenser is to be removed, the system should first be depressurized at a car service center.
10. The tappets can be removed using a special tool. On late-model engines, the tappets can be removed with a small magnet or your fingers. You can also remove the tappet with a curved scriber by prying up the retaining ring at the top of the tappet. Do not use pliers.
11. Remove the tappets and store them in the order they were originally installed so that they can be installed in their original positions during assembly (see photo).
Caution! On engines with roller tappets, the tappet limiter plates must be removed first. Do not remove the camshaft until the tappets have been removed.
12. On 1994 4.3L V6 engines, remove the balance shaft gears (see below).
13. On some V6 engines, remove the camshaft thrust plate (see photo). Screw 150mm long bolts into the camshaft sprocket bolt holes to use as handles when removing the camshaft from the cylinder block (see photo).
14. Carefully remove the camshaft, avoiding damage to the journals on the edges of the cylinder block.
Camshaft and bearings - check
15. Clean the camshaft and check the condition of the journals. If there are signs of wear on the journals, then the camshaft bearings are also worn. In this case, the camshaft and bearings should be replaced (bearings are changed at a car service center, for this you need to remove the engine and disassemble it).
16. If the journals are in satisfactory condition, then check their diameter in several places, determine the taper and ovality of the camshaft bearing journals (see photo).
17. Check the condition of the camshaft cams, the presence of traces of overheating, chipping marks and other damage. If the cams are in good condition and all dimensions are normal, the camshaft can be used further.
Pushers
18. Clean the tappets one by one and dry them, maintaining the order in which they are installed.
19. Check the wear of the thrust surface of the pusher, the rod seat and the condition of the side surface. The thrust surface of the pusher has a concavity with a large radius of curvature. If the thrust surface is badly worn (see photo), then the camshaft and tappets should be replaced. If the side surface is worn (which is unlikely), then check the condition of the holes in the cylinder block. Check the condition of the rod seats and the ends of the rods themselves.
20. The camshaft and tappets are changed only together. Put the removed tappets back in their original places.
Roller tappets
21. Check the condition of the rollers, make sure that the rollers rotate freely without excessive play (see photo). The procedure for checking roller tappets is no different from that discussed above for conventional tappets.
22.Removed roller tappets can be installed with a new camshaft, and a removed camshaft can be used with new roller tappets.
23. Lubricate the camshaft cams and bearing journals with molybdenum grease (see photo).
24. Install the camshaft in place.
25. Turn the camshaft so that the pin is in the 9 o'clock position (see photo).
26. On 4.3L engines since 1994, install the balance shaft gears (see below).
27. Install the timing chain and sprockets.
28. Lubricate the tappets with clean engine oil and install them in the cylinder block. Install the removed tappets in their original places.
29. Then assembly is carried out in reverse order.