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 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 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.


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 …


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).