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...