REMOVAL & INSTALLATION M20 Engine
See Figures 1 and 2
- Remove the cylinder head.
- Remove the rocker shaft and rocker arms.
- Remove the bolts holding the camshaft retainer and slide out the camshaft. Be careful not to damage the bearing surfaces while pulling out.
- Slide the camshaft carefully into to the cylinder head.
- Check the seals and replace if necessary.
- Install the camshaft retainer, rocker arms and rocker shafts.
- Disconnect the negative battery cable. Remove the oil line from the top of the cylinder head.
Observe the location of the seals when removing the hollow oil line studs. Install new seals in the same position.
- Remove the cylinder head. Support the head in such a way that the valves can be opened during camshaft removal.
- Adjust the valve clearance to the maximum clearance on all rocker arms.
- A tool set 11 1 060 and 00 1 490 or its equivalent, is used to hold the rocker arms away from the camshaft lobes. When installing the tool, move the intake rocker arms of No. 2 and 4 cylinders forward approximately 1 / 4 inch and tighten the intake side nuts to avoid contact between the valve heads. Turn the camshaft 15 degrees clockwise to install the tool. On these engines, to avoid contact between the valve heads, first tighten the tool mounting nuts on the exhaust side to the stop and then tighten the intake side nuts slightly. Reverse this exactly during removal.
- Remove the camshaft by rotating the camshaft so the 2 cutout areas of the camshaft flange are horizontal and remove the retaining plate bolts.
- Carefully, remove the camshaft from the cylinder head.
- The flange and guide plate can be removed from the camshaft by removing the lock plate and nut from the camshaft end.
- Install the camshaft and associated components in the reverse order of removal. Swap over the guide, flange and nut from the old camshaft to the new camshaft if replacing the camshaft.
- After installing the camshaft guide plate, the camshaft should turn easily. Measure and correct the camshaft end play. It should be 0.0012-0.0071 inch (0.03-0.18mm). Replace the guide plate if necessary to bring into range.
- The camshaft flange must be properly aligned with the cylinder head before the sprocket is installed.
- Install the oil tube hollow stud washer seals properly, 1 above and 1 below the oil pipe. The arrow on the oil line must face forward.
- Install the cylinder head. Adjust the valves.
M42 & M50 Engines
See Figures 3 through 8
- Disconnect the negative battery cable. Remove the head.
Special tools are required to perform this operation. Bmw tools 11 3 260, 11 3 270 and 11 3 250 or their equivalents are required for proper removal and installation of the camshafts and for retention of the valve lash compensators. Without these tools the camshafts will be damaged during removal or installation.
- Remove the spark plugs and attach the 11 3 260 (plus addition 11 3 270) camshaft removal fixture. Torque the hold down bolts in the spark plug bores to 17 ft. lbs. (23 Nm).
- Apply load to the bearing caps by rotating the eccentric shaft. This relieves the tension on the bearing cap bolts. Loosen and remove the bearing cap bolts.
- Remove the camshaft removal fixture after releasing the tension from the eccentric shaft.
- Remove the camshafts and the bearing caps. Note that the intake camshaft is marked `E' and the exhaust camshaft is marked `A'. The camshaft bearing are consecutively numbered with `A' or `E' to designate intake or exhaust side.
- Hold the valve lash compensators in place using tool 11 3 250 or equivalent, and remove the bearing plate along with the valve plungers.
- Inspect the camshafts and valve lash compensators for damage and wear and replace as necessary.
- Install the camshafts with the cylinder number 1 intake and exhaust cam peaks pointing at each other. The flats on the sprocket ends of the camshafts should be parallel. The exhaust camshaft is marked with a notch on the flange.
- Install the fixture. Place the bearing caps into position and press the caps down with the tool. Torque the bolts to 10-12 ft. lbs. (13-17 Nm).
- When the camshafts have been removed and reinstalled a waiting period dependent on the ambient temperature is necessary before mounting the cylinder head on the engine. At room temperature wait 4 minutes to allow the lifters to compress fully. At temperatures down to 50° wait 11 minutes. At temperatures lower than 50° wait 30 minutes. This is to prevent contact between the valves and the piston tops.
- The engine may not be cranked under the same conditions as above for a period of 10 minutes at room temperature; 30 minutes for temperatures down to 50° 75 minutes for temperatures below 50°.
S14 & S38 Engines
To perform this operation it is necessary to have a special tool 11 3 010 or equivalent. This is necessary to permit safe removal of the camshaft bearing caps and then safe release of the tension the valve springs put on the camshafts. The job also requires an adapter to keep the camshaft sprockets from turning while loosening and tightening their mounting bolts.
- Disconnect the negative battery cable. Remove the cylinder head cover. Remove the fan cowl and the fan.
- Remove the mounting bolts and remove the distributor cap. Remove the mounting screws and remove the rotor. Unscrew the distributor adapter and the protective cover underneath. Inspect the O-ring that runs around the protective cover and replace it, if necessary.
- Remove the 2 bolts and remove the protective cover from in front of the right side (intake) camshaft. Remove the bolts and remove the distributor housing from in front of the left (exhaust) side cam. Inspect the O-rings, and replace them, if necessary.
- Remove the 6 mounting bolts from the cover at the rear end of the cylinder head and remove it. Replace the gasket. Note that on the S14 engine, 2 of these bolts are longer. These fit into the 2 holes that are sleeved.
- Remove the 2 socket head bolts, located at the front of the head, which mount the upper timing chain guide rail. Then, remove the upper guide rail.
- Turn the crankshaft to set the engine at No. 1 cylinder tdc. On the S14 engine, valves for No. 4 will be at overlap position valves just slightly open with timing marks at tdc. On the S38 engine, valves for No. 6 will be at overlap position valves just slightly open with timing marks at tdc.
The next item to be removed is a plug which keeps the tensioner piston inside its hydraulic cylinder against considerable spring pressure. Use a socket wrench and keep pressure against the outer end of the plug, pushing inward, so spring pressure can be released very gradually once the plug's threads are free of the block.
- Remove the plug from the tensioner piston, and then release spring tension. Remove the spring and then the piston. Check the length of the spring. It must be 6.240-6.280 inch in length; otherwise, replace it to maintain stable timing chain tension.
The timing chain should remain engaged with the crank-shaft sprocket while removing the camshafts. Otherwise, it will be necessary to do additional work to restore proper timing. Keep the timing chain under slight tension by supporting it at the top while removing the camshaft sprockets.
- Pry open the lock plates for the camshaft sprocket mounting bolts. Install an adapter to hold the sprockets still and remove the mounting bolts.
- Using an adapter to keep the sprockets from turning and putting tension on the timing chain, loosen and remove the sprocket mounting bolts, keeping the chain supported.
- Mount the special tool on the timing case, which mounts to the top of the head. Then, tighten the tool's shaft to the stop. This will hold both camshafts down against their lower bearings. Also, mark the camshafts as to exhaust and intake.
- Remove the mounting bolts. Mark the camshaft bearing caps. It is possible to save time by keeping the caps in order, although they are marked for installation in the same position.
- Once all bolts are removed, slowly crank backwards on the tool's shaft to gradually release the tension on the camshaft bearing caps. Once all tension is released, remove the tool.
- Carefully, remove the camshafts in such a way as to avoid nicking any bearing surfaces or cams.
- Oil all bearing and camshaft surfaces with clean engine oil. Carefully, install the camshafts, marked E for intake and A for exhaust, to avoid nicking any wear surfaces. The camshafts should be turned so the groove between the front camshaft and sprocket mounting flange faces straight up. Install the special tool and tighten down on the shaft to seat the camshaft bearings.
- Install all bearing caps in order or as marked. Torque the attaching bolts to 15-17 ft. lbs. (20-23 Nm). Then, release the tension provided by the tool by turning the bolt and remove the tool.
- Install the intake sprocket (marked E), install the lock plate, and install the mounting bolts. Use the adapter to keep the sprocket from turning, and torque the bolts to 6-7 ft. lbs. (9 Nm). Do the same for the exhaust side sprocket. Make sure the timing chain stays in time.
- Slide the timing chain tensioner piston into the opening in the cylinder in the block. Install the spring with the conically wound end facing the plug. Install the plug into the end of the sprocket and then install it over the spring. Use the socket wrench to depress the spring until the plug's threads engage with those in the block. Start the threads in carefully and then torque the plug to 27-31 ft. lbs. (37-42 Nm).
- Crank the engine forward just 1 turn in normal direction of rotation. Now, 1 camshaft groove on each side should face toward the center of the head and 1 on each side should face the case boss on the front bearing cap. Lock the sprocket mounting bolts with the tabs on the lockplates.
- Reverse the remaining removal procedures to complete the installation. Before final tightening of the mounting nuts for the guide rail for the top of the timing chain, go back and forth, measuring the clearance between the sprockets and the center of the guide rail to center it. Then, tighten the mounting nuts.
The camshafts should be inspected for wear and damage. The most common form of wear on the camshafts is flattened cam lobes. It is not uncommon to find 1 or more lobes completely worn into a circle. The camshafts should be checked for wear on the bearing surfaces. The camshaft do not use separate bearing so the bearing surfaces in the head or camshaft housing should be checked. If any damage is found, the head or camshaft housing will need to be replaced.