Nothing too aggressive but whilst I had the heads off I got the Dremel out and softened the hard edges in the inlet and exhaust ports.
These edges seem to be where the cast inlet meets the machined area in the valve bowls.. With a finger it was possible to feel the lip but with a small amount of grinding and polishing it now feels smooth to the touch.
Other than removing a few minor casting marks I didn’t do much as the ports were already reasonably smooth.
I doubt it’s actually going to improve matters measurably but this was the only opportunity I’m likely to have to do it, it didn’t take long, and I can now say it’s been done.
Visited the Museum of the air battle over the Ore Mountains fought over that area in September 1944 when 60 Luftwaffe fighters (Me 109s and Fw 190s) intercepted a formation of 36 USAF B-17s shortly before they rendezvoused with their P-51 Mustang fighter escort.
They had the wreckage of a BMW 801D engine from a Fw 190A-8/R2 Sturmbock of II.(Sturm)/Jagdgeschwader 4. As this is an air/oil cooled engine of the same vintage as the 2CV the similarities are striking.
Whilst the size is significantly different (2.9l per cylinder as opposed to 0.3l) the cylinder and head assemblies are very similar with a ferrous cylinder and finned aluminium head:
Likewise, inside the head, the domed combustion chambers are very similar with one intake and one exhaust valve, hardened valve seats and the spark plug situated in the same place.
Known as Black Monday, on 11th September 1944 the USAF launched a large number of bombing raids into the Reich. The Luftwaffe put pretty much every available fighter into the air to intercept.
The FW190s involved in the action over the Ore mountains had extra armour and 30mm cannons. They attacked the B-17 boxes in a tight formation known as Sturmbock (battering ram) opening fire at under 200m. The Me 109s were there to mop up any B-17s that were forced out of formation (Herausschuss) and to deal with the Mustang fighter cover which, in this case, arrived after the Surmbock attack.
The Museum is typical of a volunteer only effort: there are a large number of items in very dense displays with very detailed and comprehensive notes.
The longer stud with the thicker band goes on the off side as there is an alternator mounting plate on that side in addition to the breather.
A new low oil pressure sender was fitted, complete with washer.
This one needed a 22mm spanner.
The oil pressure relief valve piston was liberally coated with fresh oil and inserted.
When fully home the only the nose stands proud of the housing.
The spring sits over the nose of the piston and, as I didn’t have a new copper washer, I annealed the old one by heating it until it was red hot and then letting it cool slowly.
The bolt is a 17mm and I don’t have a tightening torque for this so I went with a good strong tweak with the breaker bar which should be enough to crush the washer slightly.
Another SPOG item is the 3/4″ thread oil filter spigot. A bit of thread lock and this was firmly screwed into the oil filter mounting plate.
With a new o-ring and some sillyfoam sealant the mounting plate was re-attached to the crank case with the two alan bolts.
One of the advantages of the much more common 3/4″ thread is that a sandwich plate can be mounted. In this case I’ve got oil temperature and pressure senders – important information to have available for an air/oil cooled engine.
As I’m planning to fit an electric fuel pump I’ve got a stainless steel blanking plate for the standard, mechanical, fuel pump mounting point. This is important as, without the actuator rod, omitting the fuel pump would leave a hole in the crank case.
After applying a generous amount of high temperature sillyfoam sealant the blanking plate was secured with stainless steel M7 nuts.
There are two steps to removing the valves from a 2CV’s cylinder head, you need to remove the rocker arms before you get access to the valves.
The rocker arms sit on pivots that are held in at the top by the cylinder head nuts and at the bottom by a bolt with a special head with two flats. Fortunately an adjustable spanner provided enough purchase to free them off without needing to resort to “advanced” techniques.
Note that the head is upside down in this image.
With the bolts removed the rocker arms come free.
The rocker arms slide freely on the pivots and there are two sets of washers on them, a thick one one at the top and a spring washer and a thin washer at the bottom.
Now to remove the valves themselves. (Not too many pictures of this as it’s a job that requires three hands at the best of times…)
First a digression about how the valves are held in place. At the top of the valve stem there are a set of circumferential grooves which match the ridges on the inside of the semi-circular collets. The outside surface of the collets has a slight taper that seats them in the valve spring retainer plate that sits on top of the spring.
As that taper is constantly under pressure from the spring and will be expanding and contracting as the engine heats up and cools down it’s going to stick so, before compressing the spring, give it a small percussive persuasion to free it.
With a valve spring compressor (effectively a large C clamp) in place and the percussive persuasion having been applied it’s time to wind in the threads. When the collets are clear of the compressor collar you can go in with a magnet and extract them.
After fully unwinding the compressor to remove the tension, the valve springs lift off.
The valves then push though into the combustion chamber and can be removed.
Finally the valve stem oil seals can be removed. With the valve spring seats removed the metal collar can be prised off which allows the seal to be pulled off the valve stem.
With the crank case separated there were a few items that needed removing before they were ready to be cleaned.
First up, the oil pressure relief valve, this is a big 17mm nut on the off side
Inside there’s a spring and a plunger, which needed extracting with needle nose pliers.
On the other side is the low oil pressure sender.
In the front there’s some rubber seals for the oil cooler unions.
The oil filter mounting plate is held on with two alan bolts, one inside the filter mating surface and one at the top of the plate.
There is a rubber o-ring seal in the bottom of the plate where it mates with the crank case.
The head studs are a bit awkward but the standard stud extraction technique of a pair of nuts clamped onto each other should provide enough purchase to get them moving.
As part of the rebuild I’m fitting the SPOG oil filter adaptor, this allows the use of the more common 3/4″ 16 UNF threaded oil filters. The kit comes with a a pair of nuts that fit the M16 thread on the old spigot and, using the same technique as for the head stud removal, it unscrews.
The new SPOG spigot has the smaller M16 thread on the lower half so it fits back into the mounting plate but the larger 3/4″ 16 UNF thread on the upper to attach the oil filter.
Additional displacement has arrived from ECAS in the form of a Burton 652cc big bore kit. This ups the compression ratio from 8.5:1 to 9:1 and adds 25cc to each cylinder (an extra 8%) which should produce both more power and more torque*. Roy at ECAS recommended that a race profile cam from Kent Cams would be a good match for this as the extra breathing the cam provides will be matched by the larger displacement – all providing the fan and tinware are retained to ensure sufficient cooling.
Burton’s bench test shows an increase in torque from 6 to 7 but I can’t work out what the units are :-/
This film shows how to disassemble and assemble a Citroën 2CV engine quickly. The movie is made as an instruction for the ‘engine battle’, that we held at the AutoRai 2015. In the battle, people competed against each other assembling an engine.
This movie can be used as a guide when you’re rebuilding an engine, but be advised; some parts are skipped and missing for the purpose of the Discovery Channel engine battle instruction (for example; no liquid gasket material was used on the crankcase halves of the engine).
After removing some of the external ancillaries such as the fuel pump and the flywheel (with the assistance of Super Crack Ultra, heat, an impact wrench and a breaker bar) and leaving the oil to drain I got stuck into dismantling the engine.
Firstly I got the the jelly moulds off to drain the residual oil and reveal the valve gear.
At this point it became clear why the engine wasn’t fully turning over: one of the head studs on the off side cylinder had sheared at the bolt.
As this bolt also secures the rocker pivot axle it meant the exhaust valve wasn’t able to operate fully thus jamming the push rod, thus jamming the camshaft, thus jamming the crank. Fortunately it doesn’t look like any damage has been done to parts I wasn’t planning on replacing anyway.
With the head stud bolts and the oil feed pipes removed, the barrels and heads came away from the crank case. Whilst the near side head and barrel separated by hand the same wasn’t true of the off side (home of the malfunctioning valve) – despite application of my not inconsiderable bulk via a pry bar!
I applied a large libation of penetrating fluids and left it to marinate whilst I moved on to the crank case.
The crank case splits in half down the vertical longitudinal axis and is held together by four large (14mm) bolts in the centre and half a dozen smaller (11mm) bolts round the outside. However, there are some items that straddle the join so they need to be removed before starting on the crank case bolts.
The oil cooler needs to come off the front of the engine, firstly remove the retaining bolt above the nose of the crank shaft where the fan mounts. Then carefully remove the union bolts and ease the pipes out of the crank case.
Round the back there are a set of five 12mm bolts that hold the cap on the oil pump and below that there are two 8mm bolts that hold the oil strainer in place in the sump.
Work round the outside removing the 11mm crank case bolts – some of which are on through nuts and some on studs so make sure you check which one you’re dealing with.
Buried under the surface gunk I found one of the nuts had a washer with a long tab – not sure why but that was the only item of note.
Next up there are the four large bolts, two on each side, that go through next to the crank bearings. With those removed the crank case separates easily.
At this point it’s worth rotating the crank and looking out for the timing marks and seeing how they appear when aligned.
The timing marks are small lines marked into the gears under certain teeth. The key one (and easiest to spot) is on the crank and, when at the timing point, it will align with the edge of the crank case half at 6 o’clock.
The timing marks on the camshaft are harder to spot but there are two of them, one on each of the teeth either side of the space into which the crank timing tooth fits.
With the crankcase separated the crank and camshaft stay in the off side half and require minimal coaxing to come free.
In the time it had taken to strip the crank case the penetrating fluids had worked their magic on the off side barrel and head and they were reluctantly persuaded to separate.
That’s now the main disassembly complete and with the parts labelled and stashed away in boxes it’s time to call it a day,
As Judith is an original car, once the worn out parts are replaced there’s not going to be much to do. As a result a long term plan has been hatched to build myself a Burton to give myself an automotive toy to play with.
With this in mind an opportunity presented itself in the form of a spares-or-repair 2CV engine on fleaBay. I managed to pick it up with the opening bid as it was collection only. Fortunately it wasn’t too far from TomB engineering so he did the honours for me and reported back with some photos.
Given I’m planning on rebuilding the engine with a 652cc “big bore” kit it looks like a pretty solid foundation and having a rebuilt and bench tuned engine will open up my options when it comes to the time to find a donor car.