Norfolk Garage
Ex-militarylightweights dominate the workshop this month
The ups and downs of workshop life
while Dave the landlord has been reassembling the engine on the 1975 Series III Lightweight that he bought a couple of months ago, I have had two examples of these angular beasts in for attention.
I have always liked Lightweights, mainly because a very rough 1973 Lightweight was the first vehicle I ever owned.
Of this month’s projects, Lightweight number one was a very, very late example, VIN number in the 220,000 plus range and registered on a B-plate (1984-5). The youngest Lightweight I had previously seen was an A-plated 1983 example, built for the Royal Air Force, 12 volt and to a fairly stripped down specification with no oil cooler, civilian style gauges and various other odd features. The B-plater was a full-fat 24 volt FFR (Fitted For Radio) with all the trimmings, and I am really surprised they were making the things that late on, since this one must have been going through the Solihull factory about the same time as the first of the Ninetys to be delivered into Army service.
The vehicle had been off the road for a number of years: the engine had been removed and either lost or discarded, and the rear crossmember was in a desperate state. Various engine bay fittings were missing, the windscreen was broken, the vehicle came with a civilian hard top loosely plonked on top and the doors were piled in the back along with several boxes of random bits. It was also filthy, and the tyres were flat.
Not a promising prospect, but a quick prod around underneath revealed that apart from the crossmember and a rotten bulkhead outrigger it was actually a good, solid, largely original and unmolested Lightweight and well worth saving.
The first task was to get it mobile which meant sorting out an engine for it. I had in the workshop a 2.25 petrol engine removed from an early One Ten, and therefore of similar vintage to the Lightweight. It had been a runner when removed from the One Ten, but not an especially happy-sounding runner I must confess.
Just a few years ago 2.25 petrol engines were two a penny. I must have scrapped 20 or 30 of them over the years, because no one wanted them. Needless to say I now regret this, and I find myself having to try and salvage engines which at one time I would not have bothered with.
So I scraped the worst of the caked mud and oil off, put it on the stand and got to work.
The results were not as bad as I had feared. The older 2.25 engines (petrol and diesel) tend to suffer badly from bore wear, with the bores becoming badly stepped at the top. This engine had a bit of a wear ridge on the bores, but I’ve put the head back on much worse engines. My theory here is that bore lubrication on these engines was always a little inadequate, which is why the bores can wear shockingly badly without oil consumption increasing too much. The later 2.5 engines with the oil spray jets in the block rather than the conrods seem much less prone to bore wear. But more of spray jets in a minute.
The head was not as good as the block. 2.25 petrol heads are prone to developing cracks which start on the sharp edges around the combustion chamber, then gradually spread across the face of the head until they reach the bore sealing ring
“The air was filled with the tinkling sound of broken piston rings”
on the head gasket, at which point the engine will start eating gaskets. This head had not so much cracks as deep canyons on cylinders two and three where the hot gases had eaten away the metal around the cracks, and although they had not reached the sealing ring yet it was only a matter of time. So I set the head to one side. I will not scrap it at this stage: the damage is almost certainly repairable by a cast iron welding specialist, and although such a repair would not make economic sense right now when these heads are still fairly plentiful, I suspect that in a few years time the mathematics of repair will look rather different. I had another head acquired as part of a job lot of spares which turned out to be good, so this went away to Cambridge Rebores to be fitted with hardened exhaust valve seats and phosphor-bronze liners for the valve guides.
Removing the sump revealed no grey sludge in the bottom (bearing shell coating material) nor odd broken fragments of metal floating about. I pulled number four conrod bearing cap off for inspection and found two things: firstly the shells were newish replacements, and secondly, the upper shell had been incorrectly fitted in the conrod, with the locating tab slightly out of line with its notch. Fitting the bearing cap had squeezed the end of the shell into position, but it wasn’t right, and that meant I had to pull all the bearing caps to check for problems. None found, and the main bearings were fine as well, so I broke open a new pack of conrod bearing shells and set about fitting them.
As I mentioned above, these engines have oil spray jets built into the conrods to lubricate the pistons and bores. These are intended to point towards the camshaft side of the engine, and the relationship between the oil jet and the locating notch for the bearing shell is always the same. Each bearing cap is stamped with the cylinder number (one to four) which corresponds to the same number on the conrod, so you cannot get them mixed up.
My heart sank when I came to fit the bearing cap to the last conrod (number four cylinder), thinking I was on the home straight, and realised that the locating notch on the conrod was on the opposite side to the other three. Someone had clearly had the pistons and conrods out of the block and (I thought) carelessly refitted number four the wrong way round. To correct this the piston and conrod would have to be removed and that posed a new problem: the rings would snag on the wear ridge at the top of the bore, and trying to knock the pistons out of ridged bores has a nasty habit of breaking the rings. And you can’t just fit new rings, as the old top ring will also have developed a slight step to match the bore ridge and a new unstepped top ring will shatter the first time you start the engine. At one time you could buy special stepped top rings to deal with exactly this problem, but that was back in the good old days when engine oils were rubbish and piston rings were a service replacement item. I haven’t seen these stepped rings for sale for a long time now.
So I skimmed the sharp edge off the ridge with the Dremel as best I could without risking gouging the bore, took a deep breath, drove the piston and conrod upwards with my special tool (the wooden handle of a heavy lump hammer) and the whole lot came out with the rings intact. I double-checked the workshop manual to ensure that I had the orientation correct (oil jet towards the camshaft), refitted the piston and conrod assembly to the block, and found that the conrod notch was still the opposite side to all the others. Number four conrod and piston had been fitted correctly: it was numbers one, two and three that were the wrong way round. So I knocked out those three assemblies and the air was filled with the tinkling sound of broken piston ring fragments hitting the floor, followed by a great deal of swearing.
There comes a point at which you really should just cut your losses and give up, and I thought I had reached that point. Then I remembered something. If you read last month’s column you may recall that my work neighbour Lee had a piston disintegrate on his Series III, and that I dug up a piston and conrod salvaged from a dismantled engine. I still had the other three pistons and conrods, the bore size was the same (standard) as the engine I was working on, and being secondhand these pistons had, as you might say, pre-stepped top rings. I dug up the pistons and conrods, cleaned and checked them, fitted them and in no time at all I had the sump back on and the engine all ready to drop in.
By the end of the following day I was pouring 15W/40 oil into the rocker cover ready for start up. Fingers crossed, say a short prayer and turn the key. With the new Chinese Zenith-copy carburettor already primed, the engine burst into noisy (holes in the exhaust centre pipe) and healthy life: the oil pressure light went out after a few seconds and it settled down to a happy, stable idle. No smoke, no leaks and as smooth as these late five-bearing engines get.
There is still some work to do: with the vehicle now movable I have tackled the welding, had an initial look at the brakes, dealt with two catastrophically worn propshaft joints which must have made the vehicle pretty nasty to drive when it was last on the road, and spent a good deal of time trying to persuade various electrical items to function. The 24 volt indicator unit and hazard flasher switch seem to work perfectly happily on 12 volts, as does the heater now I have bypassed the two large resistors in a tin box on the input side. Hopefully it will be ready for MOT in the next few days: I am rather looking forward to driving it.