Refitting the Sump

Sump mating surfaces, baffle (both sides) MBP and sump-pan needed to be cleaned. The baffle had already been cleaned but was given a polish with the ro-loc bristle brush.
The MPB sump bolt holes are positioned badly in use; they point upwards and allow general muck to drop onto them. Although I had thought these were clean, I discovered this was far from the truth and I had to scrub them out using a pipe-cleaner and carb cleaner spray. At this time it also became apparent that many of the threads were damaged, partially stripped or blocked. All threads were re tapped or chased with an M8 tap. Blind holes were an additional problem because many of the bolts present were shorter than those specified in the parts list. This created a dead space in the end of blind holes which had become full of silicone from the jointing compound. This had to be carefully removed and the holes re threaded using blunt ended taps.

Using a tap to clean and repair threads in sump holes

Mating flange polished

Since some of the bolts were shorter than they should be (by about 0.5 Cm) this had probably placed too much strain on that part of the thread that they did contact. Since this was now potentially damaged I ordered new bolts of the correct length so that there would be more threaded alloy to accept the load.

Once these had arrived I was able to go ahead. I refitted the oil pick up pipe olive and torqued it down.
The sump is sealed to the motor using  a gasket sealant, but there isn't much information on how to do this as the baffle also fits in this position. I decided to apply sealant to both alloy cases, refit the sump baffle and then fit the sump+baffle to the MBP.

Sealant applied to sump, note it is placed as a bead inboard of the bolt holes. 

Sealant applied to MBP, again inboard of bolt holes

I applied sealant around any openings that would be covered by the baffle plate.

 The exact pattern in which sealant should be applied isn't given in the manual- that seems a real omission as there is a multitude of openings in the MBP and Sump and its not clear which should be sealed and which not. Some are (I think) just blind cavities but others communicate and its not clear whether they are oil or water passages and whether they need to be separated from one another by sealant forming an impervious join. I adopted the policy of sealing any cavities that would be closed by the baffle when its in position and the layout I came up with is shown above... fingers crossed!

Sump refitted- position slightly to the rear of the motor, lower and slide forward to engage oil dipstick pipe and allow oil pickup rose to slip though the baffle.

I

Refitting Pistons, rings and conrods

Old rings in position

Overall the pistons were in good condition but there was certainly some cleaning required and also the top ring had a gap which was far too large. This seemed to be due entirely to the ring rather than wear in the groove so I went ahead to order and fit new rings.

Piston as removed- 

First step was to remove the old rings which was much easier than those of the smaller pistoned motorcycles I am used to. There is plenty of flexibility and they can be slipped off by hand.

Grooves without rings- muck in top ring

The ring grooves were pretty clean apart from the top one which was dirty with a lot of sticky carbon deposit. Presumably this groove had suffered most because its closest to the combustion chamber and also had the least well fitting ring.

I cleaned the grooves using this Laser tools groove cleaner- great bit of kit and now highly recommended. I then cleaned the pistons using a ro-loc bristle brush in a hand drill.

Cleaned piston ready for new rings

I had ordered a new set of piston rings for the low compression motor (std pistons) from SJsportscars. (Steve's non Lotus alternative). The new top ring was 1.55mm in thickness instead of the previous ring (1.49) and successfully restored the correct ring gap in groove no 1. I am pretty sure that these rings are those described in the handbook as for the 907, but having checked with Steve I was assured that these are also correct for the LC 912. They do however differ from the rings removed; Ring one has no internal chamfer and can be fitted either way up. Ring 2 has an external (note not internal) step which must be oriented downwards and ring 3 is a 4 part system rather than the three part I removed. The lower oil control ring is fitted first. I had never used a 4-part ring before but the instructions I found here:
http://www.deves.com/oilring_inst.html

The set consists of an internal expander (with angular bends), a spacer ring and two rails.

Oil ring set unpacked

Fit the angled expander ring first, aligning the gap with the gudgeon pin (wrist pin)- 12 Oclock

Feed in the convoluted spacer ring, placing its gap at the other end of the gudgeon pin 6 Oclock

Feed in the lower rail, positioning its gap between the others 3 O clock

Feed in the upper rail position its gap at 9 Oclock

This is ring no 2- note the step on the outside of the ring which must be oriented downwards when fitted.

 Add the second ring followed by the top ring orienting their gaps at 1:30 and 7:30 O clock

Ring set in situ.

New  ring set in position, they were all  much more springy than the old rings  and it was particularly hard to keep the oil-ring rails in position in the groove. they tend to spring out easily and have to be checked for correct positioning several times. I checked that non of the ring gaps were in alignment and although there are probably better ways of clocking the rings I was pretty satisfied with this plan.

I removed the old shells from Top and bottom caps by pushing them sideways before clipping in the new ones...



I fitted an oiled ring compressor- checking the ring clock yet again. Its also necessary to check that the compressor does fit closely all the way round so that you can be sure that none of the rings have poked out of their grooves and become trapped on the body of the piston. Note that here the compressor is not aligned at its base (left) - this will allow the rings to spring out when they reach the bottom so make sure that the compressor looks like picture two (right). Remove the liner clamps, oil the bore and add more oil on top of the piston inside the compressor. Insert the con rod into the bore- care not to scratch the liner walls and guide the piston skirt in.  Press the compressor base firmly onto the cylinder liner edge whilst slipping the pistons down to make sure that  the rings have no gap to poke through. However be warned: The compressor does have sharp edges and from experience I would recommend gloves! Tap the piston down gently with the handle of a mallet so that it slips into the cylinder.

As soon as the piston is inside the cylinder refit the liner clamps- you will need to move the piston up and down as you fit the conrod caps and so its essential to make sure that the  liners cannot move.

Add assembly grease to the crank journals and feed the con rod down from the top by pushing on the piston whilst guiding it onto the crank with the other hand. Here the conrod has met the crank...

Before fitting the base cap and tightening the nuts- snug at first. You will need to rotate the crank to get at the nuts cleanly- so make sure the liners are clamped before you do so!

I fitted all pistons and nipped the end caps onto all. Once all were in position I removed the bolts one at a time to oil the threads. Finally I torqued down the bolts to the required 85 ftlb and checked that the crank can still rotate. Its not easy but it did turn.

Here are all 4 pistons inserted and the liners reclamped...

...and all 4 conrod caps tightened down. This motor is an early 912 but despite this it didnt have the oil breather pipe which was left off later models, I left well alone and dint attempt to fit one.











One thing I noticed though was that there was an area of damage on the alloy web of the lower MBP adjacent to the oil pickup pipe.

Some scuffing to alloy edge

This I know wasn't caused by me and checking older photos showed that it was present when I first removed the sump. I think some previous owner has struggled to get at conrod cap bolts by reaching under the oil pickup pipe at some point in the past-. I cant think why as its easier to either remove the pickup pipe or rotate the motor for access but there it is. I need a good seal here as this web will separate an oil from a water filled compartment. I checked that there are no projecting points that would prevent a good fit with the sump/baffle. The sealant should have no problem dealing with these which are not that deep and none of which go right across the web. They were there in the past so presumably had not caused a problem before.

Next job- clean up sump and baffle mating flanges.

Here we go again... refitting the modified main bearing... twice!

Well the amalgamated wisdom from both the Lotus 4seater forum and Steve at Sjsportscars was that I had indeed overdone the size of the notch in the rear lower main bearing! A triumph of enthusiasm over wisdom! When I think about it its now pretty obvious that the groove in the bearing forms a ring around the journal which is filled with oil under pressure. As there is no ready exit for this oil, it is forced out of the bearing between the bearing surface and crank journal thus lubricating the bearing. Obviously any exit of oil through the new notch would decrease the oil pressure in the groove ring and thus reduce the amount of oil spreading out across the raised parts of the bearing. Its not the depth of the groove that matters as oil can only leave where the MBP has been filed and that dimension is fixed, however the width is significant and the wide notch I had produced could allow too much oil through and drive the internal bearing pressure too low. There was nothing for it then but to take the assembly apart again and replace the bearing with one featuring a much smaller notch. Luckily the stripping was relatively simple and the MBP (main bearing panel/bearing ladder) came off again in about 30 mins.

I finally received a new grooved bearing and filed a new notch using a much smaller needle file.

Previous grooved bearing (left) and new one filed with a smaller needle file.

(right) Note that the notch no longer extends right across the groove to help

maintain oil pressure in the "ring" around the journal.

Before reassembly it was necessary to remove any old sealant and this sadly took rather a long time. I had been worried about the thickness of a layer of sealant between the MBP and block but on disassembly it was clear that in fact it had spread out really thinly forming a film across the surface of the metal over the low spots. There was nothing visible at all when the metal contacts were closely fitting. One problem was old sealant around the base of the outer (8 mm) studs). This was tricky to remove and in the end I opted to remove all the studs with a 8 mm stud extractor of the "thread-grabbing" type. This was really successful . Once the studs were out any old sealant was easily removed and I could clean up their shafts easily. I could then use the same thread grabber to re-fit the studs (with oiled threads) and torque them in to the specified setting.

8mm stud in process of unscrewing, note ring of old sealant.

 I was then able to refit the crank by laying it into the inverted block in the engine stand.  BUT... at this stage its essential to refit the spray shield. I actually missed this step the first time through; the shield must be fitted at this stage as it cannot be installed after the MBP is bolted on. Yet another strip down then!!  Fortunately the sealants weren't yet dry and it was a relatively simple matter to separate the block and panel and reseal after installing the spray shield.

This is the stuff to stick the sprayshield
onto the block. Don't use too much as it
 squeezes out when the shield is fitted

Sprayshield installed. It has to be slipped up 

from the MBP direction (step facing the block) and then 

rotated before being pressed into the housing in the block 

behind the flywheel mounting flange and lined up with the 

block on the left hand side (RHS ie out of shot in this 

view as block is inverted) 

Sealant applied to MBP

One other point that came to light since I had assembled this part of the motor was that sealant should not be applied to the main bearing pads but only around the "periphery" of the joint. Sadly this isn't defined or illustrated anywhere, and it is not a completely clear distinction since the front and rear bearing pads actually join to the "joint periphery" so who is to tell where to add sealant and where not? I made a "best guess", and extended the sealant where it seemed to form a natural line, but thinning the film across front and rear bearing pads. Since I now know that the sealant will spread out to a simple thin film I wasn't so worried about it this time around. I refitted the MBP and torqued it down (again). Hopefully this is now the last time! I still need to replace the nylon olive on the oil pick up pipe as I've had to remove it when I separated the panel and block again.

I'd intended to replace the dipstick tube grommet anyway but was surprised to find that the grommet fitted was incorrect. I found three O rings stacked up on the tube to achieve the desired thickness. Luckily I had ordered a new one anyway which I installed. I will need to check that the mating flanges are clean and not distorted so that this will seal.

Three O rings (right) found slipped over the dipstick tube and the 

single correct grommet (left) that I replaced them with.

I left the assembled block and panel to set, having checked that the crank rotated freely and turned my attention to the pistons...