Decarbonizing the head

This is  a follow up to the cleaning the valves post and its my experience with the Utube recommended method from that post. https://www.youtube.com/watch?v=7GEmuQa3dPY

I used a brass wire brush fitted into a Dremell flexible shaft drive. Overall it worked well but the job really needs a beefier driving system. Mine is battery operated and kept stalling, needing a few moments to reconfigure.

Starting condition, exhausts (top) much dirtier than inlets

Dremell flexible drive

Brass brush fitted into drive.

The Dremmel works well on the valve seats, when using it be careful to avoid in-out motions that might score a line right across the seat- try and stick to circumferential movements. The seats cleaned up easily and very well, the brush was also useful for polishing minor blemishes off the alloy inside the chamber. It was also possible to try and get the carbon off the ports... this is a VERY messy job. Dremmel or no, there is no way of avoiding getting extremely dirty and spattering the stuff everywhere! I found liberal use of diesel EGR cleaner immediately followed by the Dremelling could swirl the cleaner around the port and help to loosen the carbon- but it comes off as a sticky paste- really Yukk!

Exhaust ports nearly done...

OK- well an observation- for effective decarbonising with a Dremmell- make sure its fully charged! Overnight on the charger helped the performance of mine no end!

Lapping (Grinding) in the valves.

This spare head isn't perfect but it seemed to me that getting it ready for use might at least let me use it in emergency- or alternatively at least it keeps all the bits together in case I need any spares! I decided therefore to lap in the valves before refitting them to this head.

I started with the inlets- nos 1 and 2 went really well, the amount of grinding needed was very small- in fact "fine" paste only was needed and the effect was to create a lovely smooth grey area encircling both vales and seats.
I ground these using a hand grinding tool and using the spring under the valve approach to aid in lifting the valve between grinding sessions.

I used the time-honoured spring-on-the-valve-stem approach to aid lifting the valve for partial rotations between grinds.

Valve in position- spring lifts it from its seat

Finished effect- smooth and even circular grey region around valve and seat seen here for number 2 inlet

However it was only when I moved to valves 3 and above that the significance of something I had noticed earlier on struck me: Valves 1 and 2 are different from the other 6. They have been replaced! It seems likely that these valves have been changed (possibly their guides as well) and in all likelihood their seats have been recut at that time. I don't think the other valves received this attention and my attempts to grind the remaining valves proved far more difficult.

Inlet valves 1 and 2 (left) and 3 and 4(right)- valves are different design, although all have Lotus numbers on their stem tops. Nos 1 and 2 differ from the remaining 6.

Inlet valve 2- wide, even and smooth seat

Inlet valve 4- seat narrower than that on cylinder 1 and not even: it's narrower on one side (app 10 O'clock) than the the other (app 5 O'clock), some pitting still evident at 11 O'clock

Although I could get a nice smooth grey colour to the seats and valves it took much more work. Furthermore the seats didn't seem even, they were narrower than the bands around the valves in no 1 chamber in all places, but worse, seemed to be wider on one side than the other. Its hard to see in the pictures because the flash makes them look pretty shiny all over but it seemed clear enough to me. The chances are that these valves would seal all right but it was clear that their seats were more worn and possibly out of concentric alignment with the guides. If I was to use this head I think at the very least I would want to recut all the seats in cylinders 2-4 and probably renew valves and guides as well.

Grinding these seats is laborious and there is probably nothing to be achieved in doing so. I decided therefore to thoroughly clean the head and valves and reassemble for storage against future need. I have however got a drill-mounted lapping tool on order so I may try this when it arrives just to see if it improves matters but for the time being I'm going to stop any work on head 2 and return my attention to the reconditioned head returned from Southern Rebore.

Cleaning the valves

I decided to clean the valves of my spare head before reassembling  and  storing it. The valves were heavily carbonised but as I forgot to take any pictures I have re-photographed the process using one of the bent-ish exhausts from the other head for illustration purposes.

This valve isn't too dirty but carbon can be seen on the back of the valve, stem and some on the face. The valves for my spare head were much worse.However I've already cleaned those without pics so I'll use these for illustration only.

I got this method from a U tube video, it works really well although I'll let you know how the valves fare in use! I recommend looking at the original vid though (no its not mine and I don't get royalties!)
Check out:
https://www.youtube.com/watch?v=7GEmuQa3dPY

Wrap masking tape around the top of the stem and also just above the stem carbon deposits. Its probably best to wrap the whole stem to protect it but I found this worked fine.

Hold the valve in a pistol hand drill, make sure its straight. Grip on the protective masking tape only.

Running both the driell and a wire brush in a bench grinder angle the valve to allow the brush to remove the carbon

Rotating the valve in the drill as well as the wire brush ensure that the rubbing is even. The method is very effective and very satisfying to see. The carbon just flies off. However you must use a brass wire brush as a steel one will mark the valve.  Avoid any contact at all between the brush and the the polished valve stem.

Clean head by applying valve vertically to the top of the brush

Remove tape- clean back of valve and stem

 This is one of the actual cleaned valves from the spare head itself. It was filthy at the start but has cleaned up in a very satisfactory manner

Net result lovely clean and polished valves, all ready for grinding in (lapping) once I have cleaned up the seats.

The valve is actually better than the pictures suggest because the flash causes a distracting reflection.

I will clean the seats and ports using a small brass wire brush in a Dremmel- a flexible drive should help and I'll put some pictures up when I have tried this job.

Reconditioning the Lotus 912 cylinder head

Having removed the head from the motor in the car, it seemed to me that only the exhaust valves were damaged, the inlets being in first class condition. I should therefore only need to replace half the fittings in the head. I do of course also have the head that came with the spare motor, and although this is in good condition it has done 12k more miles and I dont think has had any new parts. It should therefore be cheaper to recondition the head from the car rather than that which came with the spare motor.- provided that a) I am right in my reasoning, and b) the head hasn't already been skimmed to its limit.

I wasn't going to do this job myself but this is a record of what was done.

Firstly I wanted to check that the head had not yet been fully skimmed so I measured its depth from the pads between cylinders 2 and 3 and also between valves 1&2 and 7&8. This value should be 82.04 mm +/- 0.254 mm. Given a maximum skim permissible of 20 thou (0.5 mm) this means that the minimum depth of head (before it's scrap) must be 82.04 - 0.254 - 0.5 which comes to 81.286 mm taking into account max manufacturing variation and max skim.

Problem: my value was only just over 80 mm!!! I was getting values around 80.2 - 80.35 mm between these three determinations.

This would suggest that the head is already too skimmed to be worth any more effort, but on checking the measurement pads between  two heads it did seem that those on this head had been deliberately ground down and now sat below the level of the cam carrier housing mating flange. This would obviously reduce the reading and if this had been done by hand might well account for variation between the three pads as I had observed.

Pad between cylinders 2 and 3. Pad seems to have been ground down; there is no flat surface to get a micrometer anvil on and the pad itself is recessed well below the gasket face for the cam carrier house.

The other head- note height of measurement pad. Grooved machined area for accurate measurement

I have no idea why this might have been done, but it does mean that perhaps I shouldn't condemn this head too soon. I will experiment with other ways of measuring the head depth. Luckily I do have a second head where I can compare measurements made in different ways. The depth of this spare head could be measured using the pad above to derive a depth of 82.18 mm. (... as an aside only Lotus would position the measurement pad opposite an opening in the gasket face making perpendicular measurements almost impossible!)

Die fitted into circular recess, can then use a micrometer to determine the head's depth.

The cam house mating surface is inclined and so lacks a clear reference point from which to measure. The surface of the head inside is flat and there is a handy machined circular  depression, but sadly the geometry of  the head prevents micrometer access to the head surface between the valves. So, as an approach to an alternative means of measuring the head, I  found that I could insert a spare threading die into the round recess between these springs as above. This has a machined surface and raises the low point so that a micrometer can now be used. Its then possible to measure the depth of the head from the top of the die to the gasket face of the head.  Measuring both heads this way shows that the measured depth to this point of the spare head (ie with the undamaged pads) is 72.28 mm meaning that the inserted die to pad height is 9.9 mm. Measuring the head with the ground down pads in the same way gives a value of  72.18 mm. The heads are thus  82.18 mm and 82.08 mm and both are still within manufacturing specs so if necessary both heads could be skimmed.


I have since also removed the valves from the second head, all are unbent although there is clear wear in the guides and/or valve stems as some sideways movement is detectable. I do not need to restore this head so I will simply clean and regrind all valves and seats before storing the head against future need.

I ordered valve guides and valves from Kemp High Performance Engines and arranged for them to be delivered straight to the engineering shop. Now its a case of waiting... but at least I can get on with the cam housing and camshafts.

Lotus Excel 912 Stripping the cylinder head

Removal of exhaust manifold. 
A few nuts were missing but the manifold came off relatively easily, two nuts coming out with their studs attached, but separated easily once out.

I cleaned the manifold and resprayed it with aluminium effect VHT paint.

The first thing I noticed about this 1984 head was that there was a line of 8 Allen screws along the exhaust manifold side

The head before dis-assembly, note row of Allen screws.

2 Allen screws per combustion chamber... what are they for

 I stripped the head by removing all of the studs using a thread-grabbing stud extractor- this worked really well and allowed me to clean around the stud bases where there was a lot of excess sealant or corrosion.

Most studs came out easily, blunt end inserted into the block first

Only one stud was actually damaged- this one had previously been repaired with a helicoil insert, but the repair unscrewed with the stud and will need doing again.

Used a motorcycle valve compressor

 I had a Sykes Pickavant valve compressor, but this turned out to be too small. I was lucky in that my Laser motorcycle valve compressor fitted well.

Compression released, collets easily removed with a magnet

Removed valve

 Here I was in for a surprise... amazingly the valves were in excellent condition! There was hardly any wear to them and most were really clean. Its as if the motor had just been reconditioned before something went wrong soon or immediately after the refit. This is hopeful and perhaps the motor had been well cared for before it had some traumatic outcome following reconditioning and then started to sink through misuse before ending up in the hands of the LBPO. Some hope perhaps?
However, all exhaust valves were very tight; All but one needed a mallet to remove them, 2 in fact were very badly bent.

Bent exhaust valve

No 1 exhaust valve spring seat was distorted (visible here at 5 O'clock position) and the seat wouldn't come out of the head. It was eventually pulled out with pliers but the head will need attention here and a new spring seat is needed.

  No 7 exhaust valve was difficult, the collets wouldn't release easily although they came out eventually, the valve guide was actually fractured across the line of the mounting circlip, half of the guide remaining in the head.

Broken Valve guide

I stored all the components in a head rack- I could have used holes-in-cardboard but this seemed nicer! It keeps all the components in the correct order and as long as I don't drop it or kick it over then all should be well.

In contrast to the exhausts, all inlet valves were perfect, nice and clean, no slop in guides and all slid in and out smoothly and easily!

Valves, springs and tappet buckets stored in head rack

I cleaned up the head with degreasant prior to measuring its thickness. However the line of screws/bolts is mystifying and given the catastrophic turn of events shortly after this head was fitted, I suppose I do have to consider that this is somehow unsuitable for the block. I really need to know more about it, so I posted a question to the Lotus excel forum... currently awaiting info. However as regards identifying this head it does have some marks...

On one end it has the lotus number: C907E0311Y on the left and a second number LN(or M)25WP above the core plug. The large number 21351 is inscribed towards the bottom of the head.

On the other end:

... a large number 83 and in a much smaller font 19KDB19 with a large letter "B" stamped at an oblique angle.

I think the Lotus No "C ...etc." is  a part number and these were numbered from the first time that the part was used... so this is a 907 head. However the part number is slightly different from that given in the manual (C907E0703J). I don't know if this is significant. Presumably 21351 is just a casting number and the large "B" a size range spec (?). That leaves me confused about the LN(M?)25WP and the 19KDB19!

Well thanks to all on the forum who helped with this. It seems these screws are blocking a line of ports used for an emission control system not fitted in the UK. They were apparently standard on all US motors and introduced to all heads sold as replacement stand alone units  and  later motors in the UK. My car is an early car so this must imply that the head at least isn't original to the car. Replacement heads sold as "stand-alones" wouldn't usually have the large casting number so this looks like a head swapped from a later UK motor. I need to check and see whether the whole motor was actually swapped at some time in the past or if it was simply the head. The  LN... number specifies a grade of aluminium for the casting. The 19K... number remains a mystery!

Back to the car... removing the head Excel 912 motor

Well- as work on the spare motor is drawing to a close and the bottom end just about done, its time, with some trepidation, to turn attention back to the car. So far I've been working in the garage and now I have to deal with all the access and positional problems inbuilt by Lotus!

Opinion is divided as to whether its best to remove the head with the engine in position or to remove the motor first. However there are 2 good reasons why I need to remove it in position:
Firstly, I don't actually know what's wrong with this motor apart from a severe and almost total loss of compression- perhaps it is fixable simply by a head overhaul and so perhaps the motor wont need to come out at all!... and secondly, I've sold my hoist with the intention of replacing it with a Sealey long-reach crane- which I don't yet have. Consequently removing the motor is out of the question at the moment... so time to tackle the head in situ.... For this I'm following (roughly) the manual plus the guide from the lotus4seater forum

Luckily for me (?) since the car has been fiddled with for a while, it came to me with some of the initial parts removed already.

Bonnet held on by two Allen cap screws, 1 each side

 I removed the bonnet- beware this is really a two-person job as its unwieldy to get the second one out without scratching the bonnet,  and then drained the radiator. The battery was already disconnected.

Radiator drain screw bottom left of radiator- hey! There really was some water left in this basket case!

The air box/trunking and the cam belt guard were already off and in the boot! Consequently the first step was then to remove the intake manifold complete with carbs.

(NB... if I was doing this job again I would NOW say... The first job is to remove the Vee belts and then the Alternator and water pump. Its sort-of suggested in the manual that you can get away with leaving these in place, but in reality you cannot! You will find it impossible to release hoses from the manifold unless the water pump is off, and you cannot access the cam belt tensioner locking nut and adjustment screw until the alternator is off. These are dealt with below when I finally realised this, but be advised- do it now!)

Overview before starting

Choke synchronisation wire fixed nicely to forward
 hand carb but...

Mounting screw nut missing from rear carb. I replaced it temporarily with the body from a cable solderless nipple to hold everything in

I disconnected the throttle cable from the rearmost carb and noted that the fixing screw lacked the rear pillar nut. I replaced this temporarily with the body from a solderless cable nipple.

Choke cable detaches from inside the car- I opted to leave it in position and move the manifold over as there is plenty of spare length to allow me to move it. Note solderless nipple now installed on rear carb choke lever. Fuel pipes are lacking outer cover so I will need to source new ones.

 I left the choke cable in position and started removing the nuts, those across the top were easy, the two at either end were more difficult.

Fuel lines were undone- the car has been standing for years and there was no fuel to spill out.

 The forward nut is behind the thermostat and has a cross bonding connection. In order to remove this its necessary to remove the front (blocked) vacuum hose fixed to the manifold and the thermostat cover... it would probably have been simpler to remove the water pump entirely at this stage but I hadn't yet removed the V belts.

Front nut behind thermostat

Remove the front  vac take off spigot to access and remove the manifold nut, very nasty looking thermostat!

Rear manifold nut is hidden beneath the rear vac take off (upper hose) for the brake servo and the HT leads and sandwiched behind the heater hose which attaches at the back of the inlet manifold

Working from the other side of the car, Remove vacuum pipe to inlet manifold in order to access the rear nut which is seen here beside the heater take off hose. Note the second cross bonding strap here- currently disconnected- need to see where that should go for reassembly.

 Even after removing this pipe take-off, the nut was still awkward- finally got it with a 1/4 inch drive socket on a wobble extn bar. Turning attention back to the pump at the front of the block in order to remove the manifold I obviously needed to detach the hose from the manifold to the water pump

Hose between inlet manifold and water pump, note water temp gauge sender inserted into thermostat housing.

This hose is virtually impossible to remove unless done at the same time as removing the pump- not at the same time as removing the manifold! I got it in the wrong order and had to cut the hose to remove it- definitely a better idea to remove the water pump before the inlet manifold. In fact this is obligatory on some cars before the head can come off anyway. I didn't think it applied to my model but I was wrong. Anyway this pipe was the last attachment and the inlet manifold could then be removed complete with the carbs. One observation is that this pipe looks like a plain straight length of pipe (as indeed it is shown on the parts list)  and not the rather more expensive pipe with a slight bend sold as a replacement for this position- a straight one being listed only for the HC motor. Has the wrong one been used here? I am  not sure which would be the best when rebuilding.

Inlet manifold removed.

 Before starting on the belts I put the motor in the timing position..

Crank timing mark aligned at TDC

... and at the same time the camwheels also aligned their timing marks and...

This is a slightly later picture (Vee belts removed) but it shows the alignment of the ignition timing mark on the auxillary pulley (hard to see but at the bottom in pic above) with the centre line of that pulley and crank pulley when engine is in timing position.

 I have no idea what will eventually be refitted, but in case I do end up refitting this head I used the paint method to simplify timing restoration. Two paint marks are placed on teeth of the ignition and exhaust cam sprockets. These are positioned in areas where the belt makes good contact with each sprocket. I could then count the belt teeth between the White marks (24 teeth) in this case. If I refit this head then making sure I have the same number of teeth between these marks should preserve the timing, however its more likely I will end up refitting a different head and re-timing from first principles.

Timing paint marks added to ign (aux housing) and ex cam sprockets, 24 teeth on belt between the marks.

I took some general views of how the vee belts were fitted...

Alternator drive belt, fitted to rear crank pulley groove and ...

Vac pump belt fitted to front groove, water pump and vac pump

Alternator was loosened and slipped inwards allowing the Alt drive belt to be removed from the pulleys although it cant come off until the vac pump belt is removed.

Lower alternator pivot bolt, loosen this and the top through bolt, push down to relieve belt tension.

Vac pump pivot bolt- loosen with a hex key socket

 Vac pump loosened at the Allen bolt and slipped inwards to loosen the belt- it remained tighter than the alternator belt but could be removed.

Crank nut loosened

Crank pulley bolt was removed by putting the car in gear and then using a breaker bar I could hit it with a mallet to shock the bolt loose against the engine and rear wheel movement. This also showed for the first time that I have a functioning clutch! The bolt came out surprisingly easily and then...

Crank pulley removed 

 To my amazement the crank pulley simply pulled off with hand pressure alone! Of course this process moved the motor from the timing position so I will have to refit and return it to that point before removing the cam belt (see on). I then tried to remove the exhaust from the manifold. Access is very limited. There are three nuts holding the exhaust to the manifold. This was good news as the manifold that came with my spare motor was broken and only really supported 1 fastening properly. I jacked up the car but couldn't even see all of these bolts and had to proceed by touch. The first nut is fairly accessible and could be removed with a socket on an extension bar.

First bolt, nut has been (relatively)  easily removed. Note engine mounting bracket above exhaust.

Second nut wasn't visible inside the curve of the exhaust but I could feel it  and eventually removed it using a stubby spanner

Second nut was invisible! But I could remove it by "feel" using a stubby C spanner

Third nut hidden behind exhaust pipes and access is blocked by the engine mounting bracket.

 The third nut was undone (eventually) using a "C" or obstruction spanner fitted around the descending exhaust pipe. I could only get a few degrees of movement and a ratchet C spanner would have helped a lot. I had expected this step to be a nightmare but I suspect firstly that these nuts (brass) were installed with a lot of anti-seize copper grease, and secondly that they may have been fitted only loosely to prepare the car for sale after the LBPO discovered that the problem was more severe than he had hoped... call me paranoid but my experience has so far taught me to distrust most of what I was told....

Water pump
Belatedly (perhaps) I removed the water pump- 5 bolts, but in my case only 4 were fitted. There should be one behind the auxillary shaft pulley but that one was missing. Tim Engel points out that this bolt is often difficult to fit or remove because it can be fouled by the auxillary shaft pulley. This has obviously happened here and rather than deal with it the LBPO simply left the bolt out. Tim suggests replacing it with a hex head cap or button bolt which has a lower head and should be accessible through the pulley. This is the pre '86 pump (note the flat area in front of thermostat housing). The pump is held on by three small upper bolts and 2 larger ones which also fit the power steering pump bracket at the bottom of the pump.

heater return hose joining to front stub pipe, short junction pipe pump to aluminium elbow to right

Hold one nut whilst undoing the next and work your way round.

Pulley removed, hoses are next

Hoses disconnected, heater pipe off, lower junction pipe detached. The inlet manifold to pump pipe was behind the pump in this view I simply cut it as it was stuck really firmly. Thermostat hose and housing was already removed.

Pump removed

Its fairly hard to get at some of these bolts and at least one looked like it will need rethreading as it was very worn. The pump sits behind the power steering pump bracket along its lower edge. This means you cant pull it forward to remove it, so break the seal by tapping downwards and then lift it up and out. This model of pump should have a gasket but was fitted with sealant alone.

Next step was to remove the tensioner and belt... however before this the tensioner needs to be slackened off. Unfortunately the tensioner adjuster is hidden behind the alternator so although I thought that I had got away with not removing it, it now had to come off.

Pictured before belt removal, The alternator(left) sits beside the tensioner(visible centre right with the cam belt going over its pulley). The alternator belt adjustment bracket is actually fitted using the tensioner-retaining bolts. In this position it  blocks access to the tensioner adjustment screw and its locking nut.

Alternator
Again this is the early type of fastening and lacks the triangular bracket, its a much simpler system. Its mounted by two bolts on the sliding bracket underneath and a single pivot bolt above. I undid these...

Alternator, lower bracket mounting bolts

... and disconnected the wiring to the alternator.

Disconnect electrical cables

There are 2 electrical connections to the alternator; a thick brown cable serving the starter motor which can be removed by folding back the rubber boot and unscrewing the nut. The smaller wire was at first a bit of a mystery, but it simply pulls off a ridged mounting stud.

Alternator upper bolt

 The upper bolt also attaches  the belt cover mounting bracket. It has a washer and spring washer in front of- and a second washer behind- the forward mounting lug. The rear lug has a sleeve/spacer which can retain the alternator once the bolt has been removed. A little fiddling was needed to get the alternator out but it came fairly easily. As usual I refitted the bolt with its washers etc in order for safekeeping.

Alternator mounting bolt reinserted for safe keeping

Tensioner
I put the motor back into the timing position and then turned it back to 90 deg btdc. This moves the pistons well down the bores and safely out of the way of anything embarrassing that might otherwise happen to them. Once the alternator was removed I could slacken the tensioner adjustment lock nut and then unscrew the adjuster- NB no more the 12 mm of  thread in  total should protrude from the tensioner body or the internal spring may fire the adjuster backwards at you.

Tensioner adjustment screw and locknut.

 The tensioner has to be retracted and locked before the cam belt can be removed or it will use its internal spring to self-destruct when the belt is taken off and fire its contents forward and all over the engine bay... good luck finding that lot! It can be locked with a 4 mm locking pin which will hold the teflon piston back against the spring... the idea being that you push the tensioner back into its body- simplest way is to press down on a run of the belt until the locking pin hole aligns with the groove in the teflon piston. However in my case...  I couldn't find the locking pin hole! The tensioner cross bonding wire is broken off as well.. I need to find out where that would usually attach on the block.

Since I couldn't use the locking pin I pushed the tensioner bearing inwards against the spring to relieve belt tension, and held it there with a plastic ratchet tie.

Ratchet tie to hold tensioner wheel in the compressed position.

I could then slide the cam belt off the pulleys; the tensioner bulged a little but remained intact. I then removed the through mounting bolt below the tensioner and the nut from the large stud to remove the tensioner itself. Note the spacers on long stud (1 at the rear, one at the front) and through bolt (1 at rear). The two rear spacers being of equal thickness, that in the front  being thinner. This explained the difficulty in finding the locking pin hole as this turned out to be hidden behind the large stud nut and washer. Having removed the tensioner I was able to press the piston back a little further in the bench vice until the hole and groove coincided. I could then fit the locking pin properly. Here the tensioner is shown fitted loosely back in position with the pin protruding.

Cam covers and cam housings
It was now possible to get on with the job of removing the head itself... and hopefully solving the mystery of the non-existent compression in the cylinders. I removed the one remaining mounting bolt from the inlet cam cover- most were missing, cams looked better than I remembered, and then removed the exhaust cover which still had all but one of its bolts... although none of the SELOC washers.

Inlet cam cover removed

Both cam covers removed, unscrewing the cam housing retaining bolts.

Once the covers were off , it would be usual to determine the tappet clearances with a feeler gauge. However I am anticipating that all the valves will be at the very least reground, and some will very likely need to be replaced, or have new guides and their seats recut. In this case all the  shim requirements would need to be redetermined anyway so I didn't bother to determine these clearances before removing the housings. The cam housing retaining bolts were undone- I used a deep 1/2 inch socket on all but a few and those that the deep socket wouldnt fit could be reached with a 1/4 inch drive socket. I was a bit concerned as these are meaty and torque-y nuts for such a small drive socket... but luckily the drive didn't break.  Before I lifted the cam housings  I placed small magnets on the tappet buckets beneath the cams to retain both tappet bucket and valve shim magnetically to the cams. I used the small magnets from a kit used to make plaster of Paris fridge magnets... my daughter got it for Christmas but only made one magnet! (See on).

All the valve shims lifted off with the cam housings, 

 Well surprise no 1- I have all the valves! I had suspected that one or two might be missing completely. I stored the tappet buckets and shims in order in a head rack (nice bit of kit that) - just in case I refit any of these components.

Magnet on top of tappet bucket...

...and valve shim retained inside tappet bucket

Cylinder head
Having removed the cam housings I could undo the head nuts in sequence as advised in the manual. These were still very tight- surprisingly as so many of the bolts I had encountered so far were either loosely tightened or absent! The rear water pipe connection has also to be removed from the head. However the head itself still couldn't be removed as there is insufficient clearance between the chassis members and the exhaust manifold. It may be possible to remove the head if (as the manual advises) you remove the exhaust manifold first; however as far as I can tell this is simply not feasible so its necessary to deal with the head/manifold combination.

There are two (related) methods for getting enough room to remove the head and both involve moving the engine.
The first requires that the left hand engine mounting be undone and the motor can then be jacked up, tilting it to the right to allow the head and manifold to clear the chassis.
The second is more drastic, the left hand mounting is undone as above but then the right hand is removed entirely. This isnt as bad as it sounds as access to this mounting is really good given the inclination of the motor. Of course you need to support the motor on a wheeled support or jack before you can do this. The whole motor can then be pushed to the right of the car on the wheeled jack to provide enough clearance. I decided to try the least complicated method first..

Viewed from under the car behind the front wheel, These are the two bolts securing the left engine mounting. One can be undone with a socket and extension but the other will need a ring spanner as the chassis blocks direct access.

 The engine mounting bolts were surprisingly loose and came off easily. The first time I tried jacking up the motor  I left the nuts on loosely at the end of their bolts as I was worried the mounting wouldn't come down in the correct place to align the holes if it were not left with some connection to guide it back down. However this doesn't give enough room, its necessary to remove the nuts entirely and then jack up the motor, Luckily the engine does drop back into the same position (almost) although it needed a little persuasion to position the mounting with a lever. I lifted the motor using a low profile trolley jack (with a plank to spread the load) positioned under the left hand side of the sump.

Engine before jacking

Jacked to right to provide extra room.

 At last I was able to remove the the cylinder head. It was however clear that the block hadn't drained fully (probably as the car is on a slight slope) and there was some escape of coolant as I raised the head. This flooded the cylinders and needed to be soaked up. I aspirated the rest out of the block using an old syringe.

Looking at the underside of the head, I had at least a partial answer to the lack of compression. Combustion chambers three and four had stuck exhaust valves- this motor has definitely thrown a cambelt at some time!

No 3 combustion chamber, jammed and bent exhaust valve

No 4 combustion chamber. One valve also stuck in raised position, nasty deposition of some form of crud along the edge of the chamber.

The bores were all very grubby and rusty at their tops. They have probably got wet, either by leakage in the head gasket, or since the car was left in the rain with no plugs in and an open bonnet. I cleaned them out with WD40 and a tissue but they still don't look great. I suspect that the rings might be rusty themselves and its pretty much impossible the clean down the side of the piston without removing them. I sprayed the bores liberally with WD40 and kept wiping it off and respraying. The jury is still out as to whether the block could be usable as it is. However, piston no 4 has also sustained some damage. There is a definite depression in its surface where its contacted the bent valve. I cant see any actual penetration but I suppose I cant rule out the possibility that the piston has been cracked, damaged or weakened. I don't really want to strip this motor as well as my spare, and anyway changing pistons will prove expensive as they should be changed as a matched set. I haven't fully decided but at the moment I think I favour swapping the motor  for the recon unit I have produced. Luckily this motor does seem to have all the ancillaries needed to fit that although I will need to sort out a head to fit.

Well  that finally reveals the LBPO for the liar he was. Throughout this strip I have found loose nuts, tricky bolts missing, peculiar threads wound around bolts to help  them grip, gaskets missing or bodged- here is a piece of cardboard used to pack the exhaust manifold for heaven's sake!

I think its pretty obvious that this motor was stripped to find the problem, and then when it was identified as a large and expensive job the motor was simply put back together (with the cam belt in the right position) for sale. I don't think its possible that the LBPO could not have known the problems with this motor and his description at the time of sale was a pack of lies!