|6 Cylinder tappet adjustment|
he sixes have a bit of a name of being less reliable than the V-8.
This however is not really necessary, with careful maintenance a six cilinder can also give many
troublesome miles! You have to be prepared to lift the cylinder head every
60,000 miles (100.000 km) to replace the head gasket. After about this time the
sixth cylinder (the one against the bulkhead) eventually finds a way to dispose of its
gases in an alternative way by blowing its hot gases through the gasket.
Off course the valve clearances should also be set and maintained properly and because of the amount of work involved this is often neglected. Yes....to set the tappet clearances the camshaft has to come off....but it really isn't so difficult as it sounds....just read on.
First make sure the engine is cold, otherwise you will get the wrong clearance settings and measurements! Getting the valve cover off is the simplest job off course but then things start going. First measure carefully the clearance of the inlet and outlet valves on the points indicated in the picture beneath. Make sure the cam is in the right position! In the drawing the cam is set to measure the inlet valve clearance. Another 180 degrees and you can measure the outlet valve clearance. This positioning has to be done carefully otherwise your clearance will be off the mark.
The inlet and outlet clearance should be 0,46 mm (0,00181inch). If the measured values for each valve are not within these limits the clearances have to be adjusted. Sadly this means the camshaft with rockers and rockershaft has to be removed.
This engine has a somewhat strange head construction. It is not just a valve cover and a cylinder head. No Rover has a separate construction in which the camshaft and the rocker shaft are mounted. This separate construction is the camcarrier. Thanx to this camcarrier we don't have to dismantle the entire camshaft construction with rockers etc. This makes changing shims somewhat easier as with a jaguar to name a brand which is famous for its overhead camshaft construction. Also notice how one lobe of the camshaft operates the inlet and the outlet valve. The inlet valve is operated directly with the use of a cam follower. the outlet valve with the help of a rocker and rockershaft construction. This is the same setup as used in the Triump Dolomites (16 Valve versions). Quite some clever guys there at Rover!.....or should I say Triumph?? because this engine was developed by Triumph engineers actually.
Preparations before measurement
Remove the timing cover and the vacuum connection and the heater pipe. Remove the Timing belt. Undo the seventeen bolts of the cam carrier and carefully lift the carrier about 4 cm. Then support the camcarrier with four wooden blocks of 4 cm height. So the blocks come between the cylinder head and the camcarrier.
Then press the cam followers onto the valves. Now the camcarrier can be removed, make sure no follower is sticking in the carrier. Check if the followers are all placed on the valves and that the shims are properly located on the exhaust valves.
Now carefully clean the camcarrier (now is the time to get rid of some sludge!) Then upon assembly grease the cam followers with multi purpose grease so that they'll stick in the camcarrier. Put the crankshaft on 45 degr. before TDC. Refit the camcarrier and tighten the seventeen bolts evenly working from the inside to the outside like fitting a cylinder head. Tighten with a torque wrench to 45 Nm.
Determination of the clearance
Carefully note for each cylinder and each valve the exact clearances. Measure the clearance of the inlet then 180 degrees further of the cam and measure the outlet of the same cylinder. This is a precise job so be careful! Then it's time to measure the thickness of the inlet and exhaust shims. Ehm....yes the cam carrier can be removed again. As I said this is a lengthy job. Now measure the thickness of the shim for each valve. Make sure that when calculating the new needed shims that if the clearance was to small you need a thinner shim. In formula form
New shim = Old shim thickness + measured clearance - wanted clearance (0,46 mm).
To make things easier here we have a tappets clearance calculator, It will work off line so don't worry of the phone bill, just save this page and use it later :
ow you know the thickness of the new shims. To the right you'll find a list
of the available shims for your 6 cylinder (in inches for mm multiply with 2,54). Never,never!
make the existing shims thinner by grinding.This is false economy. You will
go right through a wear resisant layer and within no time you will have to set the clearances again...
Fit the new shims on the right valve location, don't mix it up! Again use some grease to prevent the cam followers from dropping. Use Locktite to seal the cam carrier on the head. Again tighten the seventeen bolts with 45 Nm in the right order (from inside to outside).
Make sure to generously oil the camshaft, rockers and rockershaft. Now turn the cam until the markings align on the cam carrier and the timing wheel. Check if the position of the rotor arm corresponds with cyl. no 6. Then refit the timing belt to the correct tension. Now that your engine is open already why not replace the timing belt? It will be a long time before you need to access these components again...... (at least we hope so!). Then the rest can be refitted (valve cover, heater hose, distributor cap, etc.)
The big moment......turn the key and listen for the engine....Oh, that beautiful 6-inline sound.... why bother for a rough and uneven running V8???
Oscar Bakker "The Sixes"