REMOVAL & INSTALLATION
See Figures 1, 2 and 3
The rocker arms and shafts are retained by the camshaft bearing journal caps. Four shafts are used, one for each intake and exhaust rocker arm assembly on each cylinder head. The hollow shafts provide a duct for lubricating oil from the cylinder head to the valve mechanisms. The rocker arms are lightweight die-cast with roller-type followers operating against the camshaft. The valve actuating end of the rocker arms are machined to retain hydraulic lash adjusters, eliminating valve lash adjustment.
- Disconnect the negative battery cable. Disconnect and label the spark plug wires.
- Remove the air cleaner assembly. Remove the accessory drive belts, and detach the vacuum connections.
- Remove the valve cover.
- Before removing the rocker arm shaft assembly, a function check can be made of the auto lash adjusters. Use the following procedure:
The auto lash adjusters are precision units installed in machined openings in the valve actuating ends of the rocker arms. Do not disassemble the auto lash adjusters.
- Check the adjusters for free-play by inserting a small wire through the air bleed hole in the rocker arm.
- VERY LIGHTLY push the auto adjuster check ball down.
- While lightly holding the check ball down, move the rocker arm up and down to check for free-play. If there is no free-play, replace the adjuster.
- Install Lash Adjuster Retainers MD998443 or equivalent, on the rocker arms.
- Loosen all the camshaft bearing cap bolts. Do not remove the bolts from bearing caps. Remove the rocker arms, rocker shafts and bearing caps as an assembly.
- Remove the bolts from the camshaft bearing caps and remove the rocker shafts and arms. Keep all parts in order. Note the way the rocker shaft, rocker arms, bearing caps and springs are mounted. The rocker arm shaft on the intake side has a 3mm diameter oil passage hole from the cylinder head. The exhaust side does not have this oil passage.
- Inspect the rocker arm mounting area and rocker for damage. Replace if worn or heavily damaged. Check oil passages for clogging and clean, if necessary.
- Lubricate the rocker arms and shafts with clean engine oil prior to installation.
- Identify No. 1 bearing cap, (No. 1 and No. 4 caps are similar). Install the rocker shafts into the bearing cap with notches in proper position. Insert the attaching bolts to retain assembly.
- Install the rocker arms, springs and bearing caps on shafts in numerical sequence.
- Align the camshaft bearing caps with arrows (depending on the cylinder bank).
- Install the bolts in No. 4 cap to retain assembly.
- Apply silicone rubber sealant at bearing cap ends.
- Install the rocker arm shaft assembly.
Be sure the arrow mark on the bearing caps and the arrow mark on the cylinder heads are in the same direction. The direction of arrow marks on the front and rear assemblies are opposite to each other.
Tighten the bearing caps bolts to 85 inch lbs. (10 Nm) in the following order:
- No. 3 cap
- No. 2 cap
- No. 1 cap
- No. 4 cap
- Repeat the previous step, increasing torque to 180 inch lbs. (20 Nm).
- Remove the lash adjuster retainers.
- Install the distributor drive adapter, if removed.
- Install the valve cover. Tighten the valve cover retaining bolts to 88 inch lbs. (10 Nm).
- Reattach all vacuum connections. Install the accessory drive belts and adjust to the proper tension.
- Install air cleaner assembly. Reconnect the spark plug wires.
- Reconnect the negative battery cable. Run the engine and check for leaks and proper engine operation.
See Figure 4
- Disconnect the negative battery cable.
- Remove the upper intake manifold assembly. Disconnect and label the spark plug wires.
- Disconnect the closed ventilation system.
- Remove the rocker arm cover and gasket.
- Remove the four rocker shaft retaining bolts and retainers.
- Remove the rocker arms and shaft assembly.
- If disassembling the rocker shaft, be sure to identify all components so they can be reinstalled in their original locations.
- Inspect the rocker arms and shafts for wear and/or damage; replace components as necessary.
- If necessary, remove the pushrods. Identify each pushrod as it is removed, so it can be reinstalled in its original location.
- Inspect the pushrods for wear and/or damage. Roll each pushrod on a flat surface to check for a bent condition. Replace pushrods as necessary.
- If removed, install the pushrods in their proper locations. Lubricate the pushrod ends with clean engine oil, prior to installation. Be sure the pushrods are seated in the lifters.
- Lubricate the rocker arms and shafts with clean engine oil, prior to installation.
- If the rocker shaft was disassembled, reassemble making sure all components are installed in their original locations.
The rocker arm shaft should be tightened slowly, starting with the center bolts. Allow 20 minutes, for tappet bleed down after installation, before engine operation.
- Install the rocker arm and shaft assembly, using the four retainers. Be sure the pushrods are seated in the rocker arms. Tighten the retaining bolts to 250 inch lbs. (28 Nm).
- Install the rocker cover with a new gasket. Be sure the cover gasket mating surface is clean and smooth. Tighten the rocker cover retaining bolts to 105 inch lbs. (12 Nm).
- Install the crankcase ventilation components and reconnect the spark plug wires.
- Install the upper intake manifold assembly. Reconnect the negative battery cable.
- Run the engine and check for leaks and proper engine operation.