REMOVAL & INSTALLATION
L18, L20B, and L24 Engines
Removal of the cylinder head from the engine is optional. The camshaft cover and rocker cover are one and the same. Mark and keep all parts in order for correct installation.
- Remove the camshaft sprocket from the camshaft together with the timing chain. Refer to the Timing Chain procedures, if necessary.
- Loosen the valve rocker pivot locknut and remove the rocker arm by pressing down on the valve spring.
- Remove the two retaining nuts on the camshaft retainer plate at the front of the cylinder head and carefully slide the camshaft out (towards the front of the vehicle) of the camshaft carrier.
- Check camshaft runout, end-play, wear and journal clearance as described in this section.
- Lightly coat the camshaft bearings with clean motor oil and carefully slide the camshaft into place in the camshaft carrier.
- Install the camshaft retainer plate with the oblong groove in the face of the plate facing toward the front of the engine.
- Check the valve timing as outlined under Timing Chain Removal and Installation and install the timing sprocket on the camshaft, tightening the bolt together with the fuel pump cam (gasoline engines only) to 86-116 ft. lbs.
- Install the rocker arms by pressing down the valve springs with a screwdriver and install the valve rocker springs.
- Install the cylinder head, if it was removed, and assemble the rest of the engine.
- Start and run engine to normal operating temperature. Remove rocker cover, check and adjust valves if necessary. Install rocker cover with new gasket and check for oil leaks.
Removal of the cylinder head from the engine is optional. Mark and keep all parts in order for correct installation.
- Remove the camshaft sprocket from the camshaft together with the timing chain, after setting the No. 1 piston at TDC on its compression stroke. Refer to the Timing Chain Removal and Installation procedures.
- Loosen the bolts holding the rocker shaft assembly in place and remove the six center bolts. Do not pull the four end bolts out of the rocker assembly because they hold the unit together.
When loosening the bolts, work from the ends in and loosen all of the bolts a little at a time so that you do not strain the camshaft or the rocker assembly. Remember, the camshaft is under pressure from the valve springs.
- After removing the rocker assembly, remove the camshaft. Slide the camshaft carefully out of the front of the vehicle.
Mark and keep the disassembled parts in order.
If you disassembled the rocker unit, assemble as follows.
- Install the mounting brackets, valve rockers and springs observing the following considerations:
- The two rocker shafts are different. Both have punch marks in the ends that face the front of the engine. The rocker shaft that goes on the side of the intake manifold has two slits in its end just below the punch mark. The exhaust side rocker shaft does not have slits.
- The rocker arms for the intake and exhaust valves are interchangeable between cylinders one and three and are identified by the mark 1. Similarly, the rockers for cylinders two and four are interchangeable and are identified by the mark 2.
- The rocker shaft mounting brackets are also coded for correct placement with either an A or a Z plus a number code. See the illustration for proper placement.
- Check camshaft runout, end-play wear and journal clearance as described in this section.
- Apply sealant to the end camshaft saddles as shown in the accompanying illustration. Place the camshaft on the head with its dowel pin pointing up.
- Fit the rocker assembly on the head, making sure you mount it on its knock pin.
- Tighten the bolts to 11-18 ft. lbs., in several stages working from the middle bolts and moving outwards on both sides.
Make sure the engine is on TDC of the compression stroke for No. 1 piston or you may damage some valves.
- Adjust the valves. Refer to the Valve Adjustment procedure.
CHECKING CAMSHAFT RUN-OUT
Camshaft runout should be checked when the camshaft has been removed from the cylinder head. An accurate dial indicator is needed for this procedure; engine specialists and most machine shops have this equipment. If you have access to a dial indicator, or can take your cam to someone who does, measure cam bearing journal runout. The maximum (limit) runout on the L18, L20, L24 and LD28 camshafts is 0.02mm. The runout limit on the Z20 and Z22 series camshafts is 0.20mm. If the runout exceeds the limit replace the camshaft.
CHECKING CAMSHAFT LOBE HEIGHT
Use a micrometer to check cam (lobe) height, making sure the anvil and the spindle of the micrometer are positioned directly on the heel and tip of the cam lobe as shown in the accompanying illustration. Use the specifications in the following chart to determine the lobe wear.
CHECKING CAMSHAFT JOURNALS & CAMSHAFT BEARING SADDLES
While the camshaft is still removed from the cylinder head, the camshaft bearing journals should be measured with a micrometer. Compare the measurements with those listed in the Camshaft Specifications chart in this section. If the measurements are less than the limits listed in the chart, the camshaft will have to be replaced, since the camshafts in all of the engines covered in this guide run directly on the cylinder head surface; no actual bearings or bushings are used, so no oversize bearings or bushings are available.
Using an inside dial gauge or inside micrometer, measure the inside diameter of the camshaft saddles (the camshaft mounts that are either integrally cast as part of the cylinder head, or are a bolted on, one piece unit. The Z-series engines use a saddle-and-cap arrangement. The inside diameter of the saddles on all engines is 48.00-48.01mm. The inside diameter on the KA24E with the camshaft bracket and rocker shaft torque to specifications is 31.5-33.00mm. The camshaft journal oil clearances are listed in the Camshaft Specifications chart in this section. If the saddle inside diameters exceed those listed above, the cylinder head must be replaced (again, because oversize bearings or bushings are not available).
CHECKING CAMSHAFT END-PLAY
After the camshaft has been installed, end-play should be checked. The camshaft sprocket should not be installed on the cam. Use a dial gauge to check the end-play, by moving the camshaft forward and backward in the cylinder head. End-play specifications for the Z20/22 series engines should not exceed 0.20mm. L18, L20, L24 and LD28 camshaft end-play should not exceed 0.38mm.