CHRIS WITOR 117/29 February ’01
How to make a really clean start, plus some advice on lubrication and oils
I would regard cleanliness of the components as the most important aspect of an engine rebuild, in particular the block and its oil galleries. Any residual machining particles or dirt in the oil galleries can get pumped straight into the bearing journals of the mains, big ends, camshaft and rocker shaft. Damage can be costly in terms of either premature wear or even total bearing failure resulting in another rebuild.
Crankcase
Dirt in the crankcase should not find its way into the oil galleries, as no particles below 15 – 20 (metric) microns (i.e. 0.0005906 – 0.000787 inches) should pass through an industry standard oil filter, unless the filter is so clogged that its by-pass valve opens. I have seen an instance where the inner O-ring was not fitted to a spin-on oil filter conversion, resulting in rapid wear to the bearings on a rebuilt engine, as the oil by-passed the filter picking up more and more debris, as more and more wear took place! Apart from this, dirt in the crankcase small enough to pass through the strainer of the oil pump will wear the lobes of the pump rotors.
Another less obvious place that crankshaft dirt particles end up is embedded in the seat of the oil pressure relief valve in the block itself, preventing the valve plunger from seating properly. The valve itself can stick open even further off seat. Soft, substandard reproduction valves are especially prone to this as particles embed into the soft metal more easily. The Original, and properly remanufactured, valve plungers have a hardness of around 40 Rockwell B. A stuck open valve can result in a sudden large loss of oil pressure, whereas particles on the seat in the block cause consistent low idle pressure, particularly when the engine is hot. A good rebuilt engine should idle at between 25 and 30 psi when hot. If less, and the rest of the engine is in good condition, it is worth cleaning the oil pressure relief valve seat in the block.
I had this tool made to clean the seat. It is made from a 9/16 inch drill bit shortened and reground to 118°, the angle of the pressure relief valve seat in the block. The cutting edge angle was reduced, so that this works more like a scraper than cutter. The tool is turned by hand using the wrench shown. It is surprising what granular debris comes off the seat in some blocks. The more dirt that comes off, the larger the increase in oil pressure.
It is not only the block itself that will harbour dirt. The following components should also be cleaned thoroughly:
Rocker cover (including internal gauze in later versions)
Rocker shaft assembly
Cylinder head
Engine front plate
Timing cover
Bridge piece across n01 main bearing cap
Timing sprockets
Sump
Rear oil seal housing
Crankshaft
Connecting rods
Main bearing caps and bolts
Pistons
Camshaft
Pushrods
Cam followers
Distributor/drive gear and pedestal
Petrol pump (where used)
Oil pump
Oil filter adaptor or housing
Cleaning the Crankcase
Some engine reconditioners offer a service where the whole block is immersed in powerful cleaning agent. H T Howards of Slough use a “decarbon fluid” which removes all external traces of oil, gunge and even paint from the block. This saves a lot of physical scraping, scrubbing and brushing, especially if the block is covered in thick, sticky, black gunge.
After degreasing, I mount the block on an engine stand, and remove any surface rust with a rotary wire brush, so that the block is ready for painting later. The core plugs are also removed at this stage. I prefer to use an oxyacetylene cutting torch to remove the plugs, simply heating around the edges to red heat and blowing a hole in the middle of the plug. When cooled, they will have lost their interference fit. A screwdriver is inserted into the hole, then the plugs can simply be levered out. I prefer this to any hammer and chisel method, as there is no risk of scoring their housings.
Oil pressure relief valve, spring and nut in special blue anodised alloy. Steel nut weighed 110g (Alloy 40g)
However, despite the block being clean externally, it is never to be assumed that the internal oil galleries will be clean enough for use. The main oil gallery that runs the full length of the block should be thoroughly cleaned. The distributor/oil pump drive bush should be drifted out using a 1/2 inch shouldered drift such as a 1/2 inch socket cap bolt. This is drifted up out from its underside.
Left – late Mkl & all Mkll Right – early Mk I
The 1/4 inch BSP plug (O/E no 118632) is removed from the rear of the block using a suitable Allen key. The plug at the front of the block is a bit more tricky to remove. I drill a 1/8 inch hole through the middle of the plug. I then use an oxyacetylene torch with its intense localised heat on the aluminium plug until it just starts to melt. The plug tries to expand but has to expand inwards as the block prevents expansion outwards. When it cools it contracts leaving a loose fit in the block. I then lubricate the thread with penetrating oil, drive a flat bladed screwdriver into the soft plug and simply undo it.
The six 1/8 inch BSP plugs (O/E no 118686) can be removed from the side of the block using a 3/16 AF Allen key. If struck a sharp blow with a hammer and punch, they will normally break their hold. If this fails heat up as with the front plug.
With all the plugs removed, a rifle brush and extension can be passed through the main gallery. Wash the brush in degreaser after each pass. Rifle brushes can be purchased from a gun shop. I made my own extension out of a piece of 5/16 inch old and 24 inch long rod. I use a combination of appropriate drill bits – turned by hand – and thread taps: 1/8 and 1/4 inch BSP to clean out the cross drillings to the cam and main bearings. A 5/16 inch UNF tap is useful to clean out the many other threads of this size on the block.
Next, the block is given a thorough flush as follows:
The oil pump bush is drifted back in with a shouldered bush. Don’t drive the bush too hard as the flange nears the block as the flange can be broken off. The old pump is refitted and the block placed in a domestic water tank (cost less than £10 from a DIY superstore). The block is supported on some wooden blocks so that the strainer of the pump is just above the bottom of the tank. The oil filter and the pressure relief valve and spring are also refitted.
Twenty-five litres of new degreaser (available from any good motor factors) are emptied into the tank.
A shaft will be needed to engage the tongue and groove drive of the oil pump. A PI distributor/metering unit shaft with the gears removed is ideal. If not available make a shaft out of a 6 inch length of 1/2 inch old bar with a groove cut out to engage in the tongue of the pump. The pump turns anticlockwise when viewed from above, so a reversible electric drill with a 1/2 inch chuck will be required. I usually run the drill for about 10 minutes, swapping gallery plugs around to divert and intensify flow of degreaser through the galleries.
Remove the oil filter and pressure relief valve. The engine can be removed from the tank and put on a table, or ideally, on an engine stand to wash with hot water. Dry with a blowlamp and paint with engine lacquer. I usually put a magnet in the bottom of the tank to see how much ferrous matter has been washed out of the block. The degreaser can then be salvaged for more basic tasks. When the paint is dry the gallery plugs can be refitted to the block.
I always use a drop of Loctite pipe sealer (available from engineering or bearing suppliers) on their threads. Refitting the plug to the front of the block isn’t so straightforward. The intended stick of thread (PS1103) tends to wind far further into the block than the original, which is not reassuring. I use the 1/2 inch alloy rod that comes with a Kenlowe fan kit and run about 3/8 inch of 1/2 inch UNF thread onto the end of the rod with a circular split die and die stock. By this method the thread is more tapered. It can be wound into the block after being covered with pipe sealant, cut off flush and filed flat.
Other useful tips
If the engine has had the bores honed, or has been rebored, and new piston rings fitted always run the engine in on special running in oil. This helps the piston rings to wear/bed to their bores preventing glazing and thus premature oil consumption problems. Normal oils contain anti-friction additives which are detrimental to running in. I use Comma R05L. When the engine is installed in the car and filled with oil the reversible drill and pump drive can be used to prime the galleries, pumping oil into all the bearings and the rocker shaft before the engine has even turned.
When the assembled engine is first run with new piston rings on honed bores, a lot of ring swarf will be deposited when the peaks of honing marks wear into plateaux as the rings and bores bed in. At this stage a magnetic sump plug is highly beneficial which will pick up a lot of grey metallic paste, especially for the first 1000 miles after which the running-in oil should be changed.
Oils
Mobil 1 5w/50 synthetic oil is great for our engines, but has been superseded by thinner 10w/40 which I first tried on a high mileage 2000 engine. Oil consumption became unacceptable! My (since rebuilt) 2000 is now on Comma (who own Mobil) synthetic 5w/40, which I am evaluating. Oil consumption is no longer a problem. Modern engines use thinner synthetic oils because they create less drag, improving power output and fuel economy. If f were going to use a 2.5 engine to do a lot of heavy towing in a hot climate I would use Castrol RS10w/60. 2.5 engines run a higher crank bearing load with their longer stroke than the shorter stroke 2000. One can, of course, use cheap old 20w/50 non-synthetic oils which are relatively high in tars and waxes creating drag and thus need replacing more frequently than modern synthetic oils. Semisynthetic oils offer a good compromise.
Engine – Engine rebuilds
I don’t regard any of the oils I know of as being totally ideal. There are many compromises involved. I would ideally prefer to try 5w/45 on my 2000, which, as far as I know. doesn’t exist. However. the oil pressure does not drop below 20 psi when hot on 5w/40. The greater flow rate of a thinner oil will help cool the bearings more than a thicker oil, but a thinner oil has a lower film strength. The lobes of a high lift cam would be my greatest concern, if the oil were too thin.
It will be interesting to hear what oil other club members are trying.
Oil Coolers
These are less necessary with modern synthetic oils which are designed to cope with lubricating a hot turbo charger. A temperature gauge can be used to evaluate the situation. Cleanliness of oil cooler. hose and thermostat is essential as any dirt will be pumped straight into the oil galleries and bearings. In most cases the oil is filtered before it passes through the cooler.
Oil Pump
Very much at the heart of the matter, I wrote about this in my first Technical Article seventeen and a half years ago. (See first Register Service Notes page 1.151.) The key point for attention is rotor end float. Getting down to one thou of end float was a bit optimistic. 0.001 – 0.0025 inches is more realistic. If you have a new pump with more end float than this (0.004 -0.006 inches isn’t uncommon) then it will be beneficial to have the body machined or simply use a blue printed pump to start with.