Kugelfischer fuel injection

August 28, 2011 at 2:59 pm
filed under Fuel injection
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One comparatively rare fuel injection system fitted to some cars is the Kugelfischer system and, although it has a good record for reliability, it should nevertheless be checked and serviced at regular intervals.

Kugelfischer fuel injection is a German-made system which is fitted to certain BMW, Peugeot and Lancia models. The BMW 2002 Tii and 520i, for example, use the Kugelfischer B and C systems whereas early l,800cc Peugeot 504’s and Lancia Flavia models of the 1960’s use the Kugelfischer KF6 system. Fuel injected Peugeot 404’s use the KF1 and KF2 systems whereas the later two-litre, Peugeot 504 TI models are fitted with the KF5 system. This last system is probably the most common and is the one on which most servicing work can be carried out properly by the careful DIY mechanic.

Operating principles of Kugelfischer injection systems Kugelfischer fuel injection systems all incorporate mechanically-driven fuel injection pumps in contrast to the Bosch L-Jetronic system which is operated electronically. The type of Kugelfischer injection most likely to be encountered is the KF5 which differs from other popular systems in that it is part mechanically and part hydraulically operated.

In common with other fuel injection systems, the KF5 draws petrol from the fuel tank by an electric pump, the fuel passing through an in-line filter before it reaches the pump. There are two outlets from the pump, one going to the main filter, which is mounted on the engine bulkhead, and the other allowing excess petrol to drain back into the tank. The main filter incorporates a water trap and, like the fuel pump, has two outlets. One outlet feeds fuel to the injection pump, which is a combined metering and distribution unit, the other sends excess fuel to the tank.

The injection pump is the heart of the system. Inside the body of the unit is a camshaft which is separate from and driven by the engine camshaft via a Sedis belt. This is a flexible, toothed belt similar to the type used to drive the overhead camshaft on some cars. The pump camshaft has one cam for each cylinder and they are timed to deliver a squirt of petrol at the beginning of each induction stroke. The pistons which deliver the petrol to the injectors in the inlet ports are operated hydraulically.

As a cam on the pump shaft turns it presses against a plunger which, in turn, moves a piston to displace the hydraulic fluid. It is the fluid which moves another spring-loaded piston in the hydraulic head to push the petrol out to the appropriate injector. To control the amount of petrol delivered there is a metering arm which determines the piston’s stroke and, thus, the amount of petrol that goes to the injector itself.

Operation of the metering arm is controlled by two linkages. First, to regulate fuel delivery under normal running conditions, there is a pneumatic device housed in the dome which can be seen on top of the injector pump. Inside the dome there is a spring-loaded diaphragm which is able to move under the effects of the vacuum or depression in the inlet manifold on one side and atmospheric pressure on the other. The diaphragm bears on a regulator piston which is connected to a control rod and as the diaphragm is deflected in one direction or the other, so the rod moves up or down and regulates the travel of the metering arm.

The second linkage affecting the mixture control is the automatic choke which is attached to the side of the injection pump. The choke consists of a water jacket, fed from the car’s cooling system, inside which there is a thermostat element and a spring-loaded piston. The piston and the thermostat are both linked to an enriching lever on the side of the injection pump by a rod and the lever is linked to the metering arm. Through this mechanical linkage the enriching lever is drawn back towards the choke unit when the engine is cold. This moves the metering arm so that more fuel is delivered to the injectors in order to provide a rich starting mixture. As the engine warms up and the thermostat element reaches a temperature of 40CC , the enriching lever is automatically returned to its normal running condition.

A further sophistication on the KF5 system is the provision of an altitude corrector. This is a sealed unit which has one flexible tube connecting it to the air cleaner and another that is connected to the upper chamber of the pneumatic regulator on the injector pump. When a car is being driven on roads that are well above sea level, it is possible that the higher altitude will make the atmosphere more rarified. This means that, unless some sort of compensator is incorporated into the fuel injection system, the air/fuel mixture will alter as the engine “breathes” in the thinner air. This would lead to a richer mixture. The necessary compensation is provided by the altitude corrector. This bleeds extra air into the upper chamber of the pneumatic regulator, the amount being controlled by an atmospheric pressure-sensitive capsule inside the unit.

The basic operating principles and the layout and design of the various injection components of the KF5 system are essentially the same as those of the KF1, 2, 6, B and C designs. However the KF1 system is fitted with a manual choke attachment and the metering of the fuel with the KF1, 2, 6, B and C systems is achieved mechanically instead of pneumatically. Also, the only systems to be fitted with an altitude corrector are the KF5 and those fitted to the BMW 2002 Turbo.

Checking the engine tune

In comparison with some fuel injection systems, the Kugelfischer designs are very reliable and require the minimum of attention. Certain injection settings, such as the injection pump mixture adjustment and testing of the automatic choke assembly are usually only carried out at the car’s first service. These adjustments are critical and, consequently, should your car’s engine begin to perform poorly or be difficult to start, you should take the car to a specialist for attention. Never, under any circumstances, attempt to make the adjustments yourself.

However, as with all fuel injection systems, the state of the engine’s tune must be checked before any work on the injection system is undertaken.

First check that the air filter is clean and is in good condition. The Peugeot 504 TI models have oil-bath air filters so check that the oil level is correct and that the oil is not dirty.

The ignition timing must also be accurate and ideally it should be checked with a strobe light. The final stage of engine tune is to check and, if necessary, adjust the valve clearances.

Injection system maintenance

The first maintenance job that can be carried out is to check the oil level in the injection pump. On the KF5 system this can be done by removing an hexagonal plug on the side of the pump body. If necessary, top-up the level with a 20W oil until it just begins to dribble out the level hole. Replace the plug. The oil filler is alongside the pump body and can be readily recognized by its red plastic screw-in top.

On the KF1, 2 and 6 systems, the oil filler plug has a built-in dipstick arrangement instead of a level plug and this can be used to check the oil level in the pump. Unscrew the plug, wipe the end of its dipstick then screw it back into the pump housing. Unscrew the plug once more and note the oil level mark on the dipstick. If the oil level is far too low, 20W oil must be added through the dipstick hole until the level is correct. The recommended lubricant for these early injection pumps used to be oleo fluid but as you may experience difficulty in obtaining this, ordinary 20W oil can be used instead. However the two fluids cannot be mixed, so if you are in any doubt about the fluid in the pump, it is a wise precaution to drain out the existing pump oil and re-fill it with new 20W engine oil.

To do this, undo the drain plug on the underside of the pump, holding a container ready to catch the old oil. This drain plug may prove difficult to reach but one way to undo it is to lie underneath the car and use a socket spanner with a long extension and a universal-joint. Take care not to lose the small washer on the body of the drain plug. When all the fluid has drained out, replace the plug and re-fill the pump with clean, unused, 20W oil.

This procedure can be applied to the KF5 system as well and the job of changing the injection pump oil on all of the systems should be carried out every 48,000 km. The one exception to this rule is the B and C pumps fitted to some BMW models whose oil supply is fed from the sump. With these there is no facility for checking or draining the pump oil.

Every 20,000 km the injection air hoses should be inspected for cracks and then cleaned out as they can become partially clogged This will affect the running of the engine and its fuel consumption. To do this, remove the hoses by loosening the hose clips and pulling the hoses free. Take a suitable length of wire with a piece of cloth attached at one end, soak the cloth in petrol and pull it through each hose in turn. When replacing the hoses, make sure that the clips are tight since air leaks will adversely affect the car’s running.

Changing the fuel filters

There are three fuel filters which must either be cleaned or replaced, as necessary, every 14,000 km. The first is an in-line filter which is fitted in the fuel line between the fuel tank and the electrical fuel pump itself. Use a pipe clamp to block the fuel line coming from the tank then undo the filter retaining clamps and then pull out the filter. Reverse this procedure to fit the new replacement filter but note the arrow on the body of the filter; this must point in the direction of fuel flow.

The second filter is mounted in the engine compartment. On the KF5 system the filter casing is mounted with the altitude corrector. The water trapped by this filter should be drained out every 5,000 km. To do this, place a small container underneath the filler drain pipe, then undo the filtei drain tap. Slacken the central nut on top of the filter casing sufficiently for the filter to drain completely. Then tighten the drain tap and the central nut. Every 14,000 km the filter should be

changed. This involves draining the filter as described above but undoing the filter central nut fully to allow the filter casing to be pulled down and the filter to be removed and then replaced.

The third filter is at the fuel intake of the injection pump and is a wire mesh filter at the end of a simple banjo connection. However, since the fuel supplied to the injection pump has passed through two large filters to reach the pump, this filter should remain rela’ively clear. To clean it, undo the banjo connection, pull out the valve and clean the filter with petrol. When re-fitting the valve and the filter, make sure that the connection is tight.

When you have checked all three filters, start up the engine and closely watch all of the connections for any leaks.

Setting the idling speed

To alter the engine’s idling speed, the air bleed screw must either be screwed in or out. But before you do this, it is a good idea to remove the bleed screw and to clean out the air channel in which it operates. On the KF5 and 6 systems this bleed screw is situated at the front of the air chamber but on the earlier KF1 and 2 designs this screw is located at the back of the injector pump and is difficult to reach. The B and C injection systems fitted to some BMW models do not have this facility and consequently the engine idling speed of these cars must be set up by a BMW garage or a Kugelfischer service agent.

To clean out this air channel, undo the bleed screw lock nut and remove the bleed screw completely counting the exact number of turns that are required. A garage doing this job will now use a small brush soaked in petrol to clean the air channel but an acceptable DIY alternative is to use a thin piece of wire doubled back and covered with a clean fluff-free rag. Soak the wire and rag in clean petrol then run it up and down the air channel until the channel is free from dirt. Also, clean the end of the bleed screw then re-fit it to the air channel and screw it in by the same number of turns that were required to remove it. Then start the engine and allow it to idle until it reaches its normal running temperature. With most Peugeot models this will be indicated by the cutting in of the electro-magnetic fan for the cooling system. You will now need a tachometer to set the engine’s idling speed and if your car has a fascia-mounted tachometer this can be used. If there is no tachometer you can either fit one or use an engine function analyser. Turning the air bleed screw anti-clockwise will increase the amount of air being bled into the system and consequently the engine’s idling speed will increase. Conversely, screwing the bleed screw clockwise will cause the idling speed to decrease. The idling speed limits may be given in your car’s handbook but if they are not consult your local dealer. When adjustment is complete, tighten the bleed screw lock nut.

The air bleed screw adjustment procedure is the only way that the engine’s idling speed should be altered. On no account should you ever alter the position of the throttle stop screw as this will affect the position of the butterfly in the air chamber and will alter the minimum throttle opening of the injection system. This is a critical adjustment which calls for special tools and expertise and is a job which should be left to a garage or, preferably, to a specialist Kugellischer service agent.

Adjusting the injection pump mixture

The injection pump mixture setting should not usually need adjusting and should only be altered if the engine is performing badly or is using too much petrol. On the B and C series injection systems this adjustment cannot be altered by the DIY mechanic and should be left to a specialist who will have the necessary equipment such as a carbon monoxide meter. Similarly, on the KF2 and 6 systems, the injection adjustment screws are sealed and must not be tampered with. However, mixture adjustment is possible on the KF5 system but you will need an accurate tachometer for this job as this adjustment procedure calls for accuracy to within a tolerance of plus or minus 30rpm.

Start the engine and allow it to idle until the electro-magnetic fan cuts in. Then slacken the air bleed screw lock nut and adjust the screw until the engine speed is 900rpm for a new engine or 850rpm for a unit that has been run-in. Next, insert a long-shanked Allen key into the mixture adjustment screw which is located at the side of the injection pump close to the point where the fuel return pipe comes out. Raise the Allen key very slowly by about 3 mm. The engine speed of a new engine should now increase from 1020rpm to 1050rpm or 950rpm to 970rpm for a run-in unit. If the idling speed does not reach these figures, the engine mixture is too rich. To compensate for this, undo the lock nut and unscrew the adjustment screw a quarter of a turn. The engine’s speed will now be altered so adjust the air bleed screw to bring the engine speed back to 900rpm or 850rpm as applicable. Raise the Allen key once more and note the reading on the tachometer. Continue altering the position of the mixture adjustment screw until the correct engine speed is achieved when the Allen key is raised. Finally, do not forget to tighten fully the lock nuts which secure the air bleed and mixture adjustment screws.

Renewing the injectors

The injectors for Kugelfischer injection systems are screwed in place and to remove them, first disconnect the battery. Next, undo the clamps which hold the injector pipes together. The large nuts which secure either end of the injector pipes should now be undone. A specialist will use a purpose designed tool to do this job but, if you are careful, a good-quality, open-ended spanner can be used in its place. When the nuts of the nine have

been undone the inj xxov pipe can be lifted away. Seal the ends of the injectors and the delivery valves on the injection pump to prevent any dirt from entering. The fuel injectors can now be unscrewed but note the position of the washer between the injectors and the inlet manifold as you remove them from their seatings.

Special equipment is needed to check the injectors and this must be undertaken by a garage or a Kugeinscner service agent. But, in contrast to Bosch and Lucas injectors, a Kugelfischer injector can, in some cases, be repaired. Again however, this work can only be carried out by a fuel injection specialist.

When you fit a new injector, always renew the sealing washer between the injector and the inlet manifold. Re-fit the injector holder then tighten it to 2.0 kg’m. The injector pipes and their clamps can now be replaced. The connection at both ends of the injector pipes should ideally be tightened to a torque of 2.5 kg/m but as it is not possible for the DIY mechanic to tighten these to the correct torque without the use of a special tool, the pipe unions can only be tightened with a spanner. Take great care as these unions only need to be tightened to the extent that they do not leak when the engine is running.

If the connections leak when the engine is running, first try slackening the union and re-tightening it. Should this not cure the problem check that the connection is free from dirt. As a last resort, a new injector and pipe may have to be purchased and fitted.

Checking for fuel delivery

If the engine is running badly or misfiring at either highspeed or when idling, the fuel delivery to the cylinder may be at fault* Checking the fuel delivery is a straight-forward procedure. With the engine running, slacken the injector pipe union at the suspect injector. This should cause fuel to leak out and the engine to misfire. Tighten the union and then repeat the test with the other injectors. If the fuel delivery to one cylinder is faulty, the engine’s idling characteristics will not alter noticeably when you slacken the relevant injector pipe union nut. If the engine misfires as soon as you slacken this nut, then the fuel delivery to that particular cylinder is satisfactory.

To check whether it :s the injector or the injection pump which is faulty, interchange the suspect injector with one of the oihcrs. If die engine now misfires on the cylinder to which the suspect injector has been fitted, it is the injector that is malfunctioning and it must either be repaired or replaced. But if the engine misfires on the same cylinder as before, the delivery valve on the injection pump may require bleeding or may be faulty.

Testing the delivery valves

To check the delivery valves on the KF1,2, 6 and 5 systems, you must obtain a special tool cither from your local agent or from a Kugelfischcr service agent. This is very important for the valve has two flats on it and the only way to remove it is with the special tool. Under no circumstances should self-locking grips be used as this can damage the valve. If you cannot obtain the delivery valve tool, do not attempt to improvise but have the job carried out by a specialist. However, the delivery valves fitted to the B and C systems do not need a special tool and can be satisfactorily removed with a good quality spanner.

The delivery valves are located on the top of the injector pump and there is one valve per cylinder. To bleed a delivery valve, clean the area surrounding it thoroughly, to prevent the ingress of dirt and then remove the relevant injector pipe. Next, slightly slacken the delivery valve and then have an assistant switch on the ignition. This will cause a small amount of petrol to slowly leak from the valve, due to the action of the electric fuel pump. Then, with the ignition switched off, tighten the valve to 5.0 kg m. Re-fit the injector pipe and start up the car. If the engine still misfires, the delivery valve may be faulty. To check this, remove the injector pipe once more and switch on the ignition. Then make a note of the time it takes for the recess in the delivery valve to fill with petrol. If the valve is filled immediately or takes less than a minute to fill up with fuel then it is faulty and must be replaced.

Renewing a delivery valve is simple. Unscrew the faulty valve and screw in its replacement. It is a good idea to clean the recess of the new valve before fitting the injector pipe together with its clamps.

If, when the new delivery valve has been fitted, the engine is still misfiring, the injection pump suction valve for that particular delivery valve may be faulty. The suction valves on the KF1, 2, 5 and 6 systems are situated underneath the injection pump whereas on the B and C types of pump these valves are on top of the injection pump and are partially located by Allen screws.

A faulty suction valve cannot be repaired and instead must be replaced with a new valve. To do this, first clean round the suction valve then unscrew it from the injector pump body itself. On the B and C pumps the Allen screws must be removed before the valve can be removed. Do not forget to retrieve the filter and the “O” ring from inside the fuel injection pump once the appropriate suction valve has been carefully removed.

Clean the filter and re-fit it, along with a new “O” ring, into the suction valve aperture. Then fit the new valve but do not fully tighten it. Have an assistant switch on the ignition while you slacken off the suction valve sufficiently for petrol to flow from it. When this happens, fully tighten the suction valve. You now have to bleed the delivery valve once more on the appropriate cylindei and a quantity of suitable valve grinding paste and a valve grinding stick.

Preliminary work

Start by disconnecting the battery and, after making sure it is cold, draining the cooling system into suitably-sized containers. If one is fitted to your car, remove the fibre deflector plate from under the radiator and undo the radiator drain plug and the cylinder block drain plug. If the water and anti-freeze mixture is less than a year old, keep it in a clean container so that it can be used again. Some models may not be fitted with drain plugs on either the radiator or cylinder block in which case you will have to slacken the clips and remove the bottom hose. Whichever method of draining is used, remove the radiator cap first as this will allow the coolant to drain more easily as it will prevent a vacuum from forming. When all the coolant has drained out, disconnect and remove the top hose from the thermostat housing , die heater hose where it connects to the inlet manifold and the by-pass hose from its connection at the thermostat. Make a note to replace any hoses which are worn or perished.

Remove the air cleaner from on top of the carburettor, then disconnect the fuel pipe at its connection on the side of the carburettor and the crankcasc breather pipe from the rocker cover. Now disconnect the throttle and choke cables. The accelerator cable is released by sliding the small spring clip off the ball and socket housing , and then releasing the spring clip holding the outer cable to its bracket. Loosen the clamp bolt on the side of the carburettor and undo the small screw on the side of the choke linkage then both cables can be moved out of the way and wired to a convenient point. On some models the method for disconnecting the choke and throttle linkages may be different. If a brake servo unit is fitted, disconnect the vacuum pipe running to it. Some models, particularly those with automatic transmission, have an automatic choke. If this is the case, you must remove the heater hoses from the automatic choke unit. Now undo the two or four bolts that secure the carburettor and carefully lift it off.

Remove the fan belt and undo the bolts that secure the alternator or dynamo to its bracket. There is no need to remove the bracket with the unit but, if you do, it will give you a little more room in which to work. Now disconnect the electrical leads and take off the dynamo or alternator. Most Ford’s have a water temperature gauge fitted, so disconnect the lead at the temperature sender unit. Label the high-tension leads to the spark plugs and pull oft’ the leads, including the lead to the coil, then undo the single bolt securing the distributor and lift off the unit complete with the leads. If the coil is bolted to one of the cylinder heads undo the bolts and carefully lift it off after disconnecting and labelling the LT leads.

Removing the manifolds

Both the inlet and the exhaust manifolds must now be removed. Start with the two exhaust manifolds and undo the clamps securing the exhaust downpipes to the manifolds. Penetrating oil should help to release any nuts that are stiff. Undo the nuts that secure each manifold a little at a time, until they are all loose. If the manifolds do not come off immediately, tap them with a soft mallet or a suitable piece of wood until they become loose.

Now move to the inlet manifold. Slacken the two centre bolts first, then the four bolts at the corners, again undoing each bolt a little at a time to avoid distorting the manifold. If the manifold sticks to the head never be tempted to lever it off. Tap it gently with a block of wood or a soft mallet until it comes free. Carefully lift off the manifold and put it out of the way where it will not get damaged.

Removing the rocker gear

Undo the four bolts that secure each rocker cover to its respective cylinder head and put the covers aside. From now on, all components removed from each head must be kept in order because it is essential that all of the parts are replaced in exactly the same position because they will have bedded-in with their individual counterpart components. Start by placing the covers, with their screws, on separate pieces of clean paper marked “Left” and “Right”. The right and left-hand sides of the engine are determined from the driving scat.

The procedure for removing the rocker gear varies according to whether you are working on a British or German engine. The British engine is manufactured with the rockers mounted on separate stud pivots for each /alve. Undo the nuts on top of each stud , then lift off the small hemispherical rocker pivot assembly and, finally, the rocker arm itself. Each item should be carefully laid out in the exact order in which it was removed before being cleaned with paraffin and a soft brush.

On German Cologne engines there is a rocker shaft fitted to each cylinder bank, mounted on two pedestals on the top of each cylinder head. Undo the two securing bolts evenly, a turn at a time, until they are free and the rocker shafts can be lifted off. Clean the assemblies with paraffin and a suitable soft brush.

If the rockers are worn, on the British engine they can be replaced individually; on German engines, the rocker assembly has to be dismantled. Individual rockers are also available for the German engine but Ford recommend that if any of the rocker gear components are worn, the complete assembly should be replaced. However, if you do decide to replace rockers individually, the procedure is as follows. First take out the roll pin from one end of the shaft followed by its spring washer. You will now be able to slide off the rockers, the supports and the springs but make a careful note of their order so that the shaft can be re-assembled correctly. When re-building the shaft take care that the oil holes are clear and that they point downwards towards the cylinder head. You can check whether you have it right because there is also a notch on one en”d of the face of the shaft and this should also be nearest to the cylinder head. On both models lift out the pushrods. The most convenient way to ensure that you do not get confused is to push them through a piece of stiff card marked “Top”, so that the rods go back the right way round and “1 to 6 right-hand bank” and “7 to 12 left-hand bank” so that they go back into their original positions.

Removing the cylinder heads

It is most important that the cylinder head bolts are slackened in the correct order and a little at a time to prevent possible distortion of the head.

Undo each bolt progressively no more than half a turn at a time until all of them are loose, then slowly lift off the heads. If the heads do not come free immediately, try tapping them with a block of wood or a soft hammer. If this does not work, turn the engine over by hand, with the spark plugs still in place and the pressure generated by the pistons in their bores should free the head. On no account should you try levering the heads off as you will almost certainly damage their faces and the face of the cylinder block. This will result in the need for expensive machining work to re-face the components. Making sure that you do not confuse the left-hand and right-hand heads, move them to your workbench and then remove the old head gaskets from the cylinder block.

If you have noticed that your engine consumes large quantities of oil now would be a good opportunity to check the cylinder bores for wear, using a Vernier gauge. If you find that they are worn beyond the manufacturer’s recommended tolerances, which you can get either from your handbook or your local dealer, a re-bore or a re-conditioned engine may be necessary. If you do need a re-conditioned engine there is no point in continuing with the decoking operation, as you will have to exchange your car’s existing engine unit when you buy the replacement.

Removing the valves

To remove the valves you will need a valve spring com-pressor. A special tool is available from Ford but a universal C-shaped compressor is an equally effective device for this purpose.

The valve must be held against its seat while the valve spring is compressed so that the spring retaining collets can be removed. Fit the compressor and tighten the screw thread until the spring is compressed far enough for the two split collets to be lifted out. The two collets are fitted into a small groove in the top of the valve stem and you may find it helpful to use a screwdriver or a pair of long-nosed pliers to get them out. Once the collets have been removed carefully unscrew the compressing tool until the tension on the valve spring is released then remove the tool and lift off the valve spring, the collar and the valve stem oil seal. Now carefully push the valve down its guide and out through the combustion chamber. As with all other mechanical components, keep these in the correct order so that they can be re-assembled in their original positions.

Decarbonizing the cylinder heads

Remove the spark plugs from the heads and you can then begin the work of decarbonizing. This is often an extremely dirty operation so lay down plenty of old newspaper first. Clean one head at a time, starting with paraffin and a soft brush to remove any oil or grease from the outside of the unit. This will also help to soften the carbon deposits. It is possible to use a blunt scraper to clean off the carbon but this is an extremely laborious process; a far better method is to use a rotary wire brush fitted in a portable electric drill. Before starting push wads of tissue into the valve guides to prevent any carbon dust from entering, then use the wire rotary brush to clean all carbon from the combustion chambers and the exhaust ports. Take care that the chuck of the drill is not allowed to come into contact with either the valve seats or the exhaust port lips as damage may be caused. Use a soft brush to clear all of the loose carbon dust and finish the job by cleaning the heads in paraffin once again, then lightly rub the head over with fine-grade, wet-and-dry paper before giving them a final clean with a soft, paint brush.

Cleaning the valves

The valves will also need careful decarbonizing and for these the best tool is again a rotary wire brush. Put each valve in a vice using soft jaws or blocks of wood to protect the stems, then carefully clean all of the carbon deposits from the stems and the valve heads; you will certainly find that the exhaust valves have a thicker build-up of carbon as they

reach a far higher temperature than the inlet valves. When you have finished cleaning the valves lay them out in the original order so they can be re-assembled correctly.

Cleaning the cylinder block faces and the pistons

All traces of the old cylinder head gaskets must be removed from the cylinder block faces before the new gaskets and the heads can be replaced and it is best to complete all of the cleaning work before you commence re-assembly. First, protect the cylinder bores with tissue, clean fluff-iree rags or a layer of grease, then use a soft scraper in order to remove any traces of the old cylinder head gaskets from the mating faces of the cylinder block.

It is possible to clean the carbon from the top of each piston as well but this is not really necessary. If you do decide to do this, only clean the centre of the pistons, leaving a perfect ring of carbon round the outside. This is important particularly if your engine has a fairly high mileage, because there is bound to be a certain amount of wear in the piston rings or the cylinder bores and this ring of carbon will help to act as an oil and compression seal.

Examining the components

Once all the components are clean you can inspect them for wear or damage. Remember that if you do find wear in one component, you must decide whether it is worth replacing the one unit, or whether it would be better to replace a complete assembly altogether.

Start by inspecting the valves. If any are cracked, seriously burned or pitted you will certainly have to buy new ones. Small degrees of pitting on the edges of the valves can be rectified when the valve is ground in. Check also on the condition of the valve seats in the cylinder heads. If they are heavily pitted you will have to re-cut them. Check with a steel rule that the cylinder head faces are completely true and check the complete head for any signs of cracking. If any cracks are apparent you may be able to get the cylinder head repaired by taking it to a specialist, otherwise it will have to be replaced. Place each valve in its guide and, taking hold of the stem, attempt to rock it. A small amount of play is acceptable but if it is excessive the cylinder head will have to be taken to a specialist to have new guides fitted. On the Ford V6 engine this is not a DIY job. Finally, check the rocker assemblies for wear or pitting and then the pushrods to make sure that none of them are bent.

Grinding in the valves

To grind in the valves you will need a valve grinding stick and some coarse and fine valve grinding paste. Now take each valve in turn and place it in its original position in the cylinder head. Attach the suction cup of the grinding stick to the head of the valve and smear a small quantity of coarse grinding paste around the valve seat. Now carefully rotate

Valves open

1 and 6

8 and 11

2 and 3

7 and 10

4 and 5

9 and 12

the stick backwards and forwards between your palms, lifting it slightly every few seconds to distribute the grinding paste evenly. Use a clean rag to wipe off the coarse paste and then finish oft’ using fine paste. The valves and valve seats should have an unbroken light grey appearance when you have finished. It is most important when you have finished grinding that every trace of grinding paste is removed using clean rags and paraffin because if any is left behind it will cause a great deal of damage when the engine is started because of the abrasive nature of the paste. Repeat the grinding in operation with each valve.

Re-assembling and re-fitting the cylinder heads

Firstly, re-fit each valve, in its original position, lubricating its stem with clean engine oil. Fit the new oil seals from the decoke gasket set. If any of the valve springs are broken or weak they will have to be replaced but if the car has done a high mileage since the last top-end overhaul, say 32,000 km it is best to replace all the springs as a matter of course. Place the valve spring over the valve stem, ensuring that the three close coils are fitted next to the cylinder head assembly, then fit the collar over the spring with the centre boss facing downwards. Now carefully fit the valve spring compressor on to the valve and tighten it until the spring is sufficiently compressed to allow the split collets to be fitted into the groove in the valve stem. The easiest way to position the collets is to hold them on the end of a small screwdriver with a blob of grease. When both of the collets are securely in place, slowly release the tension on the valve spring compressor, checking that the collets remain in place as the spring collar comes past them. If the collar is slightly off-centre it could dislodge one of the collets.

Thoroughly lubricate the “tappets” and replace them in their original positions if removed earlier. The heads are now ready to be re-fitted. Position the head gaskets on the block; they are marked cither “Top Front” on British engines or “Oben Vorn” on German engines and this lettering should be positioned at the front of the engine. Now re-fit the cylinder heads. The two heads are identical but you should always fit them in the original positions because otherwise the pushrods and rocker gear will be subject to excessive initial wear as the two unmatched components become bedded-in. Tighten the cylinder head bolts as far as possible by hand. Use a torque wrench, tighten each bolt a little at a time to 7 kg m , then 8.4 kg m and finally to 9 to 9.7 kg,m.

Re-fit the pushrods in their original positions with the cupped end uppermost and re-fit the rockers over each stud or re-fit the rocker shafts on German engines, making sure that all the components are well lubricated. Tighten die rockers or rocker shafts evenly. Place the inlet manifold gasket in position and apply jointing compound to the mating face of the manifold to ensure a

good seal. Next, position the manifold between the cylinder heads, with the thermostat housing at the front as before. The six securing bolts should be tightened progressively, a little at a time to a torque of 0.7 kg m , then 1.4 kg in and finally to 1.8 to 2.2 kg m. Do not over-tighten the bolts as you may crack the manifold which is made of alloy.

Adjusting the valve clearances

The valves are numbered 1 to 6 front to rear on the right-hand bank and 7 to 12 front to rear on the left-hand bank. All valve clearances are checked when the valves are fully closed and the table below shows the relationship between the fully opened valves and the closed valves to be adjusted.

Adjust

10 and 7

5 and 4

9 and 12

6 and 1

11 and 8

2 and 3

The clearances should be set at 0.254 mm for the inlet valves and 0.457 mm for the exhaust valves. These clearance figures are the same for a hot and a cold engine and should be re-checked after the engine has been run for a short length of time.

Re-fitting the ancillaries

Basically, re-fitting the ancillaries is the reverse of the removal procedure but you should always fit new gaskets where applicable and, to ensure the best possible performance and economy from your engine, you should fit a new set of contact breaker points and spark plugs, properly set to the manufacturer’s specifications. Check the condition of the distributor cap and the HT leads and examine the radiator and heater hoses for any signs of damage or perishing. If necessary, fit new items at this time.

Re-fill the cooling system with the recommended quantity of water and anti-frcc/.c and check the oil level, topping it up if necessary. You can now start the engine and allow it to reach its normal running temperature. Re-check the torque of the cylinder head bolts and the valve clearances after 15 minutes of running time then re-fit the rocker covers, using new gaskets. Re-connect the crankcasc breather pipe. Your car is now ready to be road tested. You should immediately notice an improvement in both power and economy if the overhaul has been carried out properly in accordance with the instructions given in this article.

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