Big ends and Crankshaft- remove and check

I am rapidly building up a list of items to measure on this motor- been putting that off because my measuring skills aren't that great, but hey will have to come to terms with it soon. However before I can measure the crank journals I have to remove the con rods and bearing panel or ladder retaining the crank itself.
Disconnecting the big ends was fairly simple, I started at no 4 because this is the area where the pistons were marked so presumably any damage would be in nos 4 and 3.

No 4 Big end cap

Hard to photograph but conrods and caps already
identified with number- in this case "4". 

I scratched numbers onto the conrod bolt heads as I  would like to reuse. in the case 4A and 4B, "A" referring to the bolt on the left hand side when motor inverted- ie inlet side.

The caps are undone a few turns breaking the torque with a breaker bar- no too hard, then give the bolt heads a tap with a soft mallet to pop the shells off the journals, unscrew the rest of the way and remove the pistons (CAREFULLY) by sliding piston and attached rod up the cylinder- take care not to scratch the bore with the con rod end. I found that the liner clamps I had made allowed the rings to pop out and I could remove the pistons fully without removing the clamps- they will have to come off for installation though.

No 4 big end journal

... and no 4 big end shells in place

Stamping to rear of shell

Quite frankly this all looked very good to me. The Journals were smooth and unmarked and looked in great condition. The main shells did show some wear but they have to wear as they bed in and nothing here looked excessive, simply well seated. There was no scoring to either the journals or the shells and this was not the cause of the muck in the oil filter. The markings to the rear of this shell suggested that the crank has been reground to -20 and this certainly suggests that some sort of repair may have been carried out in the past.
I removed the other 3 pistons and rods in the same way...

Journal No 4, Note stamping to bearing ladder

Journals 2,3 and 4 Rear of motor to right

Journals 1 and 2

... and all were very similar. I am beginning to think that this motor was reconditioned and is actually in good enough condition to simply reassemble, however I may fit new shells at least. I will check on the meaning of the figures on the shell back before ordering a new set. I still need to get a micrometer on the journals to check for wear and out of round; but as it seems to have been ground to the maximum already I am hoping that there will be no such problems as that would mean a new crank 

Pistons and rods. 

The pistons similarly looked in fair to good condition. All rings free in their grooves, there was no sign of combustion blowing down the skirts below the rings in any cylinder. All pistons did have striations or marks to their lower skirts but these were marks rather than scratches and I couldn't detect any scoring with a fingernail. Similarly there were a few vertical streaks in the cylinders and also a few marks (stains?) but nothing that would catch a nail. I suspect that this is all in good condition with some marks from storage but all might benefit from a hone to clean up the bores a little, perhaps new rings would help too? I still need to measure the bores and check for ovality, check that the rings are standard like the pistons and check the ring gaps- I probably wont do all of them unless there is a problem as rings are fragile and expensive and so far my attentions to this motor have largely been unnecessary- serving only to provide a chance to make things worse! Ah well at least I am learning!

All 4 pistons in plastic tray

Pistons have absolutely no vertical play at the small end/gudgeon pin junction. They do however slide smoothly and easily sidewise. I am satisfied that these are OK and I wont be dismantling the set further- unless I decide to fit new rings.

view up bore, no 4 cylinder, all look really similar.

Main Bearings

So far I have not been able to identify any significant wear in the motor- there is some as there must always be, but not enough to account for the swarf in the oil rose. I will need therefore to look at the mains and thrust washers. The mains are a potential problem as this motor is number 20363. Lotus fitted a modified main bearing ladder from engine number 20875  to prevent premature wear of the thrust washers. Engines earlier than this received a makeshift modification to their bearing ladder performed either by Lotus themselves during assembly (engines 20793-20874); or to be performed by a service engineer whenever the motor was next stripped (engines Prior to 20793). This modification consisted of filing a chamfer to the bearing ladder at no 5 position and installation of a notched main bearing shell not used by motors after 20875. My motor clearly falls into this last category and so I cant tell whether that main bearing was modified or not. Of course this does mean that if the bearing panel has either not been modified at all, or modified but fitted with the more common and incorrect (plain) bearing, that the thrust washers might wear too  rapidly and this would be a very satisfying explanation for the coppery swarf in the oil pick up filter.

 I suspect one way of checking whether the thrusts are damaged may be to check crank end float, although I doubt that this is always definitive and I'm not sure that the state of disassembly that my motor is in currently will allow this test, so overall (and despite my trepidation) I probably do need to remove the crank to see what has been done.


On a practical note it is getting hard to see how I could support the motor whilst I remove the bearing panel or ladder. The engine stand was originally secured in 4 threaded holes. One was in the sump and had to be detached when this was removed. This left three, but now holding a lightened motor lacking head and sump so it has so far been OK. Removing the bearing panel would mean detaching another clamping bolt leaving just 2 which is clearly not going to be enough! I will need to rearrange the clamping bolts if there are suitable threaded holes, or detach the motor and break this joint on the bench- This will be awkward as I really want the crank uppermost which means supporting the motor inverted- but the cylinders are inclined and have head bolts protruding. Further I will need some considerable force to undo the bolts, and off the stand it will be hard to steady the motor. Ah well...  life would be boring without challenges.

Removing the Bearing Panel or Ladder

It took a while to reposition the tear-down stand. In the end I had to re-sling the motor from the crane and reattach the support rods from the stand end plate. It took a couple of attempts but eventually I got 4 good supports. One of the these was routed though a starter motor attachment bolt hole and secured with a nut. I had avoided using these mounts before because I didnt want to bend the motor end plate. However now the motor is so much lighter- and will be lighter still when I remove the bearing panel and crankshaft I think I should get away with it.

Re-slung motor fastenings reallocated so all attach to cylinder 

block leaving the bearing panel free for removal.

 Now attached the motor could be inverted and the crankshaft end float measured. This was surprisingly easy, connecting a dial gauge as shown, although the reading face is positioned down and away from the camera. End float was determined as 0.21mm which is just over the recommended range of 0.08 - 0.2 mm, but still below the maximum permissible wear of 0.3. mm.

End float determination, gauge reading face downmost

 I was then able to remove the nuts from beneath the bearing housing taking the smaller nuts off first, loosening from the edges diagonally towards the centre. These were surprisingly dirty/corroded but none-the-less unscrewed easily with the breaker bar. One stud came out with its nut and will need to be detached.

Loosening bearing panel nuts

Before removing the panel I took note of how the oil splash shield had been fitted, although this was difficult to photograph, these pictures show engine inverted and from the rear

Note bent locating tab

End of flange cutout

The bearing panel needed a tap to release the seal but could be removed easily revealing the main bearings below. The upper shells remained attached to the panel and the crank remained in the block.

Bearing ladder inverted after removal, note main bearings in order with plain bearing in centre- mains 5-2

Mains 4-1, plain bearing in position 3.

There was no appreciable wear to the mains although they did seem to be in worse condition than the big ends. Number 5 main had the rear grooves plugged with sealing compound which might have impaired lubrication, I'm not really sure whether this channel is intended to allow oil movement.

Note sealant blocking the oil drain channel (?)

and partially blocking the opening on the other side.

The bearing panel had not been modified as per Lotus instructions, both sides of No 5 bearing cap were unchamfered and the expected notched shell was not fitted. Close ups of both edges to the no 5 position are shown below. Photo taken from underneath the panel from the rear

No 5 position in Main bearing panel (shell removed). 

Note that there is no chamfer to the edge of the bearing recess. 

No 5 position in  Main bearing panel (shell removed), 

panel inverted, note lack of chamfer to edge.

It was possible then to lift the crankshaft out of the remaining bearing shells in the block, leaving the shells behind.  The oil deflector fell out at this stage so just as well I had noted its location. The main bearings in the block were in similar condition apart form bearing shell 4 lower, this did show some evidence of scoring. However the crank was undamaged in this position o I assume that the bearing material has performed one of its tasks and accepted the wear caused by some contaminant protecting the crankshaft itself. 

Lower Shells 5 and 4

Lower shells 3 and 2

Lower shell no 1 main bearing

Scoring visible on lower shell no 4, this could catch the 

edge of a nail!

However the corresponding journal was undamaged

In fact all the main bearing journals on the crank looked to be in good condition but will need to be measured to be sure they have not worn.

Crank lifted out, all journals look good to me

The rear of all mains shows a value of 010 so the mains have presumably been reground to 10 thou undersize

Thrust washers were present and showed some wear, however this was confined to very specific areas at the corners.

Inner thrust washer in situ

... and removed, note wear to upper edges

Rear of thrust washer marked STD

The rear thrust washer was more worn, measuring it showed some 3-4 thou of material had been worn awayand this might account for some if not all of the coppery material noted in the pick up filter.

Copper face of rear (outer)  thrust washer, note wear pattern to surface.

In conclusion there was still nothing to account for all the fragments in the oil pick-up filter. I think it is possible that these are old materials but in any event I am currently hopeful that the motor can be reassembled fairly simply. I need to determine whether to fit new shells and I probably will, however the mains do present a problem as the expected modification to the panel and shell wasn't present. It is always possible that  the panel itself has been changed for the modified later version in which case no modification is necessary so I will check before I can be certain which bearings I actually require in the no 5 position. The crankshaft looks very nice but still requires checking for size and roundness. The most significant crank wear is actually in the region of front and rear oil seals so I will try to reposition the seals on reassembly such that their lips avoid these wear marks. This I am hoping is the lowest point of the rebuild. The engine is just about as far apart as it can get- and certainly as far as I want to strip it, so hopefully from here on things will be going back together.