Author: Website Administrator

87/16 February ’96

GENTLE WARNING

This series of technical articles has been designed for the “mechanically minded” reader who feels capable of carrying out his own maintenance to this degree. If you have doubts about your ability to cope with the instructions you are earnestly advised to leave the job in the hands of an experienced mechanic. During the combustion of the petrol air mixture of an engine, deposits of carbon are formed. Although the majority of these deposits are ejected through the exhaust system, a certain amount remains and collects on the walls of the combustion chamber, valves and piston. This build up of carbon prevents the engine from breathing and robs it of its performance, in the same way a fire loses its brightness when the chimney becomes blocked with soot.

Very high temperatures are also produced during combustion, which are necessary for the running of the engine. The high temperature and heavy loads exerted on the valves will sometimes cause them to burn after very big mileages. The question now arises as to when a decoke and valve grind are necessary. To give an answer in terms of mileage on this question is virtually impossible, as no two engines are alike. The best guide is in the symptoms; the loss of compression is the key. Loss of compression will cause loss of power, heavy petrol consumption, difficult starting and uneven running, and even misfiring. As the fall in performance is gradual it is often not noticed until the condition gets very bad.

EQUIPMENT REQUIRED
1. A set of ring and open-ended spanners from 3/8″AF to 3/4″AF.
2. Valve grinding stick.
3. Screwdrivers, one large and one small.
4. Grinding paste, coarse and fine.
5. A scraper or rotary wire brush if available
6. Valve spring compressor.

SPARES REQUIRED
1. A set of decoke gaskets.
2. A set of exhaust valves.
3. Spark plugs, points, and hoses etc. as and if required.
Obtain your spares from a Triumph parts supplier and always quote your engine or commission number you are then certain of getting the correct parts.

REMOVAL OF THE CYLINDER HEAD

Whenever working on an engine the first safety precaution to be carried out is to disconnect one of the battery leads.

There are quite a lot of components connected to the cylinder head and other parts of the car, these all have to be removed or disconnected. Drain the Cooling system by the tap on the lower tank of the radiator (if fitted). All the hoses can then be removed including the heater hoses and manifold heating hoses on the Triumph 2000. After unscrewing the clips, give the hoses a twist to break the seal. This will make them easier to remove. Slacken off the dynamo / alternator mountings and remove the fan belt. The water pump can now be removed by unscrewing the three securing bolts, the top right hand bolt also secures the dynamo / alternator stay, the left one the petrol pipe. All three are just above the water pump pulley.

There are only a few electrical points which require disconnecting. These are simply the water temperature gauge, if one is fitted, and the H.T. leads to the sparking plugs. To save damage, remove the distributor top. It is also a good idea to number the leads, thereby preventing them from being connected to the wrong plug.

The carburettors can be removed with the manifold as a complete unit or separate. Disconnect the throttle, and choke controls, remove the air cleaners and disconnect the petrol and vacuum advance pipes. If the manifold and carburettors are being removed as a unit, disconnect the exhaust pipe. A single row of bolts and two nuts, one at each end secures the manifold to the head, these can be removed and the manifold lifted off.

Having removed all the controls and components from the head we can now start removing the head. Unscrew the nuts securing the rocker cover; these have fibre washers and plain washers under them, the fibre washers to prevent oil leaks. Removal of the rocker cover gives us access to the rockers themselves. The rockers are mounted on a shaft and are removed as a complete assembly which is secured by 9/16″AF nuts, one on each pedestal. From each rocker there is a push rod connecting it to the cam follower. When removing the push rods give them a shake, this will free them and prevent dislocation of the cam followers.

With the rocker shaft and manifold assemblies removed we can now have access to the cylinder head nuts, which can now all be removed. The cylinder head nuts are all high tensile nuts and should not be mixed up with other nuts of the same size, so keep them separate. If in doubt about the correct nuts, the high tensile nuts are identified by the letter “R” on the upper face.

The lifting can sometimes be difficult to start with, as sticking sometimes takes place between the faces of the head block and gasket. A slight sideways tap with a piece of wood or soft hammer sometimes helps. The cylinder head removed and on the bench, we can now concentrate on the valves. Removal of the valves from the head is one of the most difficult tasks to be encountered on the decoke.

A special tool is used to compress the spring; this relieves the pressure on the two collets allowing them to be removed. After releasing the spring compressor, the valve cap, springs and valves can be removed. If the compressor is not available the springs can be compressed by placing a block of wood under the valve heads and using a strip of metal pivoted on one of the rocker pedestal stands. When removing the valves from the head, mark them so they can be replaced into the same guide. When new valves are being fitted this is not necessary of course. Clean off the deposits from the valves and combustion chamber, and clean out the ports. A rotary wire brush in an electric hand drill is a useful tool for this job. Wash all loose dirt from the head so it is nice and clean for examination.

Inspect the valve seats for bad pitting. If the seats are too badly marked, they will have to be cleaned up with a special cutting tool; this is best done by a garage. The valve guides are also best removed and replaced by a garage if they are worn at all. Worn valve guides cause heavy oil consumption and reduce valve life considerably. To check a valve guide, place the valve into the guide so it is about 1/8″ off its seat. Then try rocking it from side to side. There should be no more than .020″ movement. A worn guide can also be detected by looking at the stem of the valve; a dull black deposit of carbon on the stem indicates wear on the guide.

Assuming the valve seats and valve guides are in order, we can start grinding in the valves. This is done by smearing the valve seats with grinding paste. Before putting the valve into the guide, lightly oil the stem. Using the valve grinding stick rotate the valve back and forward using the palms; rotate the valve occasionally allowing the paste to return. While grinding in the valves gradually rotate them so they are seated all the way down. Ensure after grinding in, that all the grinding paste is washed off, as an abrasive will produce wear if left in. Inspection of the seats will show if the valve has been ground in correctly. The seat both on the valve and head should have an even mat grey mark all the way round about 1/10″ wide. Too wide a seat will collect foreign bodies.

(Were there any Mk1s factory fitted with non-six cylinder engines? – Uncle Stan Part)

ANDY ROBERTS 45/08 April ’89

The manual says that oversize thrust washers were not fitted to the 2500 engine, and therefore some engine reconditioners only supply standard thrust washers. There is no reason why you can’t fit oversize thrust washers to a 2500 engine, and if the end-float is outside limits with the standard washers every reason why you should. Note that the allowable endfloat on the 2000 is 0.006″ to 0.014″, whereas on the 2500 engine it is only 0.006″ to 0.008″. This is what the book says, but I am a bit sceptical! Certainly 2500 engines seem more prone to dropping their thrust washers than 2000’s, but I would not worry until the end float exceeds 0.014″ in either engine. Thrust washers are available 0.0025″ and 0.005″ oversize, which of course reduce the endfloat by 0.005″ or 0.010″ respectively, since there are two of them.

(Ed’s note -You can use a standard one and an oversize one to give endfloat reductions of 0.0025″, 0.005″, 0.075″ or 0.010″!). (Other oversizes are also available – Uncle Stan Part).

GEOFFREY SHOTTER 16/04 June ’84

Don’t rush out and remove the entire front suspension as some manuals suggest. Merely remove the front crossmember leaving the struts in position, and avoiding the necessity to disconnect the brake-lines. This then becomes a straightforward nut and bolt job. Power steering does add slightly to the work, but air expulsion is very much easier than brake bleeding. Please do change big end bearings at 30,000 mile intervals. It’s only a days’ work and it will pay dividends in crankshaft life. If you do the mains as well, don’t remove them all at once and let the crankshaft drop – it damages the oil seals which then leak profusely and that means another Saturday under the car. (You don’t actually need to remove the cross-member, just undo it and pull it forwards. Disconnect the anti-roll bar, if fitted. – Uncle Stan Part).

MARK UNDERWOOD 12/10 October ’83

Tuning means different things to different people and is therefore a rather difficult subject on which to write. Generally speaking tuning means:
– greater performance with greater efficiency without too much detrimental effect on fuel consumption;
– greater reliability
– greater speed capabilities with an increase in torque
– better handling of the vehicle.

It is pointless to tune any motor car by adding on bits or improving the characteristics of an engine with large increases in horsepower and torque, without improving the handling and braking of the vehicle, without which the full benefit of the extra power cannot be properly utilised, and is therefore wasted. (The post-68 2000 has the same brakes as the 2.5PI – Uncle Stan Part). With the general introduction over, it is absolutely imperative that no penalties whatsoever can be assumed by myself or the Register, nor is it my intention or the Register’s to recommend that any individual owner carry out any modification that would be contrary to the law, i.e. the Road Traffic Acts or Construction and Use Regulations.

Members must also be aware that in any modification of a motor vehicle, certain risks are inevitably involved. Only those who believe they are mechanically competent, with the necessary tooling to undertake the suggested modifications and procedures are advised to do so. This is mainly because neither I nor the Register can assume or accept any responsibility for any damage or injury that may occur as a result of following the procedures and modifications.

It is also imperative that when working with the engine, gearbox, or axle, that absolute cleanliness be observed. Prior to working with these units have them steam cleaned if possible. Ensure that your working surfaces are clean and that you have a plentiful supply of clean rags. For safety’s sake ensure that the working area is well lit and also ensure that you have a plentiful supply of hand cleaner as frequent washing of one’s hands whilst working with oil and grease will leave them not only presentable at the end of the day, but will make handling of awkward items that much easier. It is also a good idea to have a large dust sheet available to cover up the units while you are not working on them.

THE CRANKSHAFT

The crankshaft is one of the weak points in the “Big Six” engine, being only a four main bearing crank and therefore not very well supported. It is therefore limited in its capabilities as to the amount of power it can take. Despite this weakness the crank has proven itself to be very resilient to abuse, and breakages are very rare. The most common problem is that the thrust washers when worn, and sometimes when fairly new, have a nasty habit of dropping into the sump. You may have guessed the end result… not a pretty sight. Manual transmission cars suffer engine “knocking” (bearing wear) within rather low mileages due to continual clutch movements, clutch judder etc, whereas auto transmission cars hardly suffer from this problem until high mileages are encountered, as a result of the transmission, so to speak, being able to soak up violent crank movement.
On removing the crank first visually check for signs of scoring or deep scratches which may make the crank unsuitable. Scratches can be felt by running your nail across the journals. The next step is to measure each of the journals to ascertain that they do not have an out of round condition (in other words not oval) not exceeding 0.0010″, or that they are not flat exceeding 0.0005″. Once checked that the crank falls within these specifications it is than safe to reuse it after it has been crack tested, micro polished and balanced. However, if the unit does not fall within the specifications given (which is normal on a worn engine) proceed as follows:
– have the unit crack tested,
– machine to an appropriate undersize,
– micro polish and balance.

Your local engineering firm will advise you on what other parts are required for them to complete the balancing procedure.

Before assembling crank into block, carefully clean all the oil passages with a small fibre brush, such as a fine rifle bore brush. Use copious quantities of cleaning solvents (paraffin or Gunk) for the initial cleaning, and repeat to finish off with hot soapy water. Blow the crank and its passages dry with compressed air. At this stage DO NOT oil the journals and throws unless you intend to refit the crank into the block immediately. If you do oil the crank, and leave it lying around the oil will merely attract dust and grit and other nasties which can prove extremely harmful. Keep the crank clean and dry until ready for reassembly. Do not wipe the journals with a rag as they leave traces of lint that can enter and foul the lubrication system.

On the assumption that the block is ready to receive the crank, slide new (Vandervell) main bearing shells into position. Lightly oil the shells with a fifty-fifty mixture of good grade oil (GTX) and STP, or alternatively engineers lube, and lower the crank carefully into position.

Next fit the rear crank thrust washers suitably lubricated, followed by the other half of the main bearing shells fitted into the bearing caps. Just before fitting, with a can full of oil, squirt a few shots of oil into each of the oil passages in each journal. Once the caps have been fitted using BRAND NEW bolts, torque down each cap in turn according to the specified torque settings. (New bolts may be required on 2.5 engines, but they are not usually necessary on the shorter stroke, lower stressed 2000 – Uncle Stan Part). After all main bearing caps have been tightened rotate the crankshaft to ensure that it is not binding. Then check crankshaft end float with the use of a dial gauge. Oversize thrust washers are available if the float is found to be excessive (more than 0.010″).

Also essential in a tuned engine is that the crankshaft is hardened after the machining process. This hardening process is essential for long life of the unit (See Stu Harvey’s article 7.2.1, 12/14 – Ed). Either Tuftriding or Nitriding can be used, both having the same end result, with an increase in the wear and fatigue properties of the unit being treated. My own engine had covered 180,000 plus miles on a standard crank so treated without any problems whatsoever. (Nitriding can only be used on EN40B billet cranks. Don’t tuftride new cranks; the residual stress can lead to distortion – Uncle Stan Part).

THE CYLINDER BLOCK

The block is immensely strong and as such does not require any modification. For outright competition high power applications, or for the real enthusiast, it will be necessary to establish zero surface clearance – the distance between the top of the block and the top of the pistons at top dead centre. It is a complicated procedure requiring skill and a lot of patience, with the aid of special gauges. The process is the same whether old or new pistons and con rods are being used, both requiring the engine to be assembled in order to take measurements. Firstly thoroughly clean the top of the block so that every trace of gasket and carbon are removed. Next, mount a dial gauge in such a manner that each piston TDG (top dead centre) can be ascertained, bring No.1 piston to TDG and measure the depth with a depth micrometer between top of piston and top of block. Also measure NO.6 piston at the same time, and record the measurements in tabular form. Rotate the crankshaft to obtain readings for No.2 and No.5, and then No.s 3 and 4. It will now be seen that you have a record of all depths obtained. Again I stress that this operation must be carried out with the engine assembled, using either old or new parts. You cannot take measurements with the old pistons, and then install the new ones, and vice-versa otherwise you will be in a terrible mess. The idea behind all this, as you may have now figured out, is to correct these measurements so that they are all exactly the same, and that all parts will be the same length or height, and takes into account the differences in con rod lengths and piston compression heights (and crankshaft stroke throw – USP) during manufacture. The average clearance on a standard block is around 0.015″ to 0.017″. From the measurements obtained, find the highest value and add 0.005″, and have this resultant figure skimmed off the face of your block. This will ensure that further measuring and machining will not be required at a later stage. Once all machining is completed the block can be taken to bits and faced off.

As far as reboring and fitment of new pistons is concerned, refer to your factory manual for guidance and clearances. On this subject, ask for the bores to be finished off by hand honing with fine stones. If the block is not to be rebored and merely re-ringed, again have the bores honed by hand so that a clearance of 0.004″ to 0.005″ between piston and bore is achieved. This will ensure that any slight tapering of the bores is removed, and it also provides an excellent surface for the bedding-in of the new rings.

CAMSHAFT BEARINGS

Unfortunately in its standard form the block of the 2000 and 2500 does not have removable camshaft bearings. The camshaft itself runs in straight cast iron bores in the block. However it is possible to fit sleeve type bearings of the removable type, although this is really only necessary for real outright power applications. The procedure for fitting these bearings is really quite easy and is not overly expensive. (Necessary for a tuned 2000, if you use more than 6000 rpm with strong valve springs. 1995 cost £200 approx. – Uncle Stan Part). To start with you will need 2 pairs of Triumph Spitfire camshaft bearings (Vandervell part number 142648). These have the same internal diameter as the camshaft journals. The next stage is to take your bare block to the engineers and ask them to line bore the block to the required diameter using the camshaft as a dummy thereby ensuring the correct fitment and clearance after the bearings have been fitted. Don’t forget to fit a new cam core plug at the back of the block, using a good epoxy glue such as Araldite Rapid. We can now consider that all the machining work is complete, and we come to the most important procedure there is when rebuilding an engine – the cleaning procedure. The motto here is to scrub, scrub, and clean, clean until spotlessly clean. To enable this to be carried out with the minimum fuss, remove, and I mean remove, all brackets, oil plugs, all studs, and ancillary equipment. Scrub outside and inside the block faces so that all the oxidised oil deposits and other rubbish are removed, and all faces should end up having a nice dull sheen about them. Again use a rifle bore brush to clean out all the oilways etc. Scrub the bores and oilways with copious amounts of hot soapy water and paraffin so that all swarf, grit, dust, etc. is removed. This is absolutely essential, as if this procedure is not carried out properly it can only mean short engine life, thereby causing extra work in another rebuild, extra expense, and a general drain on your resources. Just be patient and take your time, otherwise you’ll end up in the long term pulling your hair out. All too often I’ve seen some eager beaver just merely wipe down the block, assemble it quickly, and out on the road again, only to find that the nice new engine is back out of the car again in 500 miles. Post mortems have revealed that swarf had not been properly removed. You have been warned …

Reassembly consists of replacing all oil plugs using Loctite Studlock or similar, as this will prevent vibration causing the plugs and studs coming loose in later life. This should only take place after all the oilways have been blown out with compressed air. At th is stage it is a wise move to paint the block with either Hermetite Engine Lacquer or Finnegan’s Smooth rite to the colour of your choice. My personal preference is for about 4 coats of engine lacquer, red at that, resulting in a beautiful finish that is hard wearing and doesn’t fade with the heat produced. Red is chosen quite simply as it shows the slightest trace of oil leak from the engine, and it motivates me to keep it clean. Once the block has been painted, cover it with a cloth and allow the paint to harden for a few days. The airing cupboard is the best place, when the wife is out! If she creates you can always use the excuse that your back has suddenly “gone” and you need a few days rest before removing it.

Follow all the engine reassembly procedures in your manual and you can’t go wrong. Remember, take it easy, don’t rush things, and recheck what you have just done, and you will soon end up with a handsome unit that will give you many thousands of miles trouble free motoring. Good luck …

THE OIL PUMP

I have little to offer on the excellent article written by Chris Witor (1.1.5, 10/17). I’m glad he has done this as it has saved me a lot of time and energy. One vital point to remember is that the oil pump and the oil are the heart and blood of your engine. Any dirt that is picked up by the blood soon finds its way back to the heart with the end result that the pump has a coronary, and bang. If you have not fitted an oil pressure gauge then go out and buy one, and fit it. It is a very useful instrument that can tell you much about the state of your engine and oil. Frequent “reading” will give you ample warning of any impending disaster. (Alternatively, use a 20psi oil pressure warning light switch, instead of the standard one which works at 3 to 5 psi. Use running-in oil if you have fitted new pistons or rings – Uncle Stan Part).

STU HARVEY 10/15 June ’83

Rod Barber, our worthy Chairman (Ed’s Note – and Editor!) has just been obliged to strip his PI engine after only 32,000 miles since a total rebuild. Having examined the main and big end shells I can see an advanced state of wear for such a low mileage. Assuming that the machining and reassembly was correctly carried out – it ran very well and quietly up to a few weeks ago – what exactly happened is a mystery.

The only explanation I can put forward (and have seen like before) is that some residue of “swarf” from the machining process has remained in the oilways of the block (from a rebore) and / or the crankshaft (from a regrind). In my experience some engineers specifically tell you to clean out all the oilways yourself, and some say “nowt” , and some say that the remachined units are ready to be rebuilt. Being a cynic (and a coward) I always thoroughly clean all the oilways and channels etc. I was told once by an engine specialist that the best method is to use a hot water, high pressure jet. If possible I use this but have resorted to garden sprays, bicycle pumps, etc. as available. The main thing is to get all the muck out of the oilways as it is a mixture of emery dust, carborundum grit and particles of the metal removed by the machining process – not the ideal “running in” compound. The hot water for cleaning can be blown out with compressed air or displaced by pumping clean oil through the oilways (an ordinary pressure type oil can will suffice).

While carrying out this operation don’t forget the small holes that feed the rocker shaft. Also remember that the hole is continued up through the cylinder head and any valve lapping paste or grit from valve reseating operations must be removed . This of course may have nothing to do with Rod’s trouble, but it does seem possible that something nasty may have been left behind.

When discussing this aspect of Rod’s engine at a recent Chiltern Group meeting, Chris Witor inspected the bearing shells and whilst agreeing that my theory could be the possible cause, asked why we were using Glacier bearings and not Vandervell, which he reckons are of much better quality and last a lot longer, but do not cost any more. (They do cost more nowadays! – Uncle Stan Part).

By the way, I heartily endorse the advice given in the last issue to replace the oil pressure relief valve plunger and spring periodically. The seating does wear, in which condition it could contribute to “late” oil pressure delivery.