Norfolk Garage
Why it’s sometimes better to repair rather than replace
Ever since childhood I’ve been fascinated by internal combustion engines of all shapes and sizes. There’s something magical about the way an engine converts fuel into forward motion. The variety of ways in which this can happen is almost endless – petrol, diesel, rotary, four-stroke, two-stroke, supercharged, turbocharged. Everything from a single-cylinder lawnmower engine to the 28-cylinder, 3500 hp Wasp Major aero lump operates on the same basic suck-squeeze-bang-blow principle.
As soon as I was old enough to walk I was helping my father to repair whatever scrap yard refugee we had as our family car at the time. Helping, at that age, consisted mainly of picking up some oily bit of Ford Anglia or Bedford Beagle that my father had placed on the ground, gazing at it in wonder and then dropping it into the gravel. By the time I reached my tenth birthday my father had found a way to distract me: I unwrapped a large box to find a Keil-kraft balsawood model aircraft kit, and a small single cylinder diesel engine which ran on a mixture of ether, castor oil and amyl nitrate, was a pig to start and had a habit of shaving off your fingertips on the sharp-edged propellor if your starting technique wasn’t quite right. It did nothing to cure me of my addiction to engines.
My £250 Triumph Herald
I spent much of my teens fiddling around with old lawn mower engines, so by the time I bought my first car I already had a pretty good idea of what the inside of an engine should look like, and some understanding of the principles on which it worked. When my £250 Triumph Herald turned out to have no oil pressure and a horrible death rattle from the bottom end I had no hesitation in dropping the sump and pulling all the bearing caps. The bearing shells were worn down to the backing metal so I bought a new set and learned two things. First, it is possible to change the main bearings in a Herald without removing the engine. Second, if a component (in this case a bearing cap) does not locate itself the way it should, the correct approach is to remove it again and investigate. Instead I tightened down both cap bolts, not realising that the locating tongue on the upper shell was out of line with the corresponding notch in the block. The result was a badly-bent bearing shell, which meant that I had to order another set. I had gouged the crank as well, so the new bearings lasted a month. At least I had learned something.
Series IIA diesel
By 1991 I was well into old Land Rovers, and built up a 2.25 diesel engine outside on the grass on a beautiful spring day. It ran a lot better than it should have done, being put together using the least-bad bits from three old engines. The best way to become familiar with a particular type of engine is to dismantle a few of them, and since those early days I must have pulled apart a couple of hundred fourcylinder Land Rover engines ranging from early 151 petrol engines to 300Tdis. The Land Rover pushrod four evolved over time, and you can trace a direct line of descent from the original 1957 Series I diesel engine to the 300Tdi, even though the two engines only share a single component (the spigot bush in the back of the crankshaft).
As a result I can sometimes mix and match components from engines of different ages and types, and I’ve had a couple of good examples of this approach come into the workshop of late.
The first was the Series IIA diesel that I mentioned last month. The original plan for this was to use the block from a type 12J naturally-aspirated diesel engine, with a 2.25 five-bearing crank and the cylinder head from the dead 2.25 that had come out of the vehicle. After further discussion with the customer we agreed to build the engine up as a 2.5, since diesel Series vehicles are a bit underpowered in standard form. So I ended up building a 2.5 diesel with chain-driven camshaft and vertical injection pump. This turned out to be surprisingly easy, but you need to have the correct type of engine block. Early 12J engines had the front end of the block fully machined to take a Series-type timing chain tensioner: all that’s required is to extract a small blanking plug from the oil way that feeds the tensioner, and tap in two locating dowels either side of it. Later engines don’t have the slot for the tensioner nose and cannot be converted in this fashion.
The Series timing cover will fit straight onto the 12J block although new bolts will be needed: almost all Series engines were assembled with Imperial fasteners, whereas 12J engines are metric. When fitting the sump you then have to remember that the front three sump bolts
(the ones that screw into the timing cover) need to be Imperial threaded. The Series timing gear drops straight into the 12J block and is timed up in the usual way, with intense concentration and a certain amount of swearing. It’s a horrible design, and I would love to know how the Solihull engine plant workers managed to cope on the production line. The gear needs to be fitted so that the master spline for the pump drive is at 20 degrees to the centre line of the engine. It’s a skew gear and rotates as it’s lowered into position, so you have to guess the starting point required to achieve the 20 degree end result. The gear has a rounded top and is very difficult for pliers to get a good grip when you find it is one tooth out and need to extract it and start again.
The gear runs in a brass bush that’s retained by a grubscrew that passes through the block from the outside and locates in a hole in the bush. As the gear is lowered, the bush has a nasty habit of rotating in its housing, so that once the gear is in the correct position the locating hole is no longer in line with the grubscrew, and there’s no way of seeing where it is, and no easy way to realign the bush in its housing with the gear fitted. Meanwhile, as you’re wrestling with all this nonsense, you’re also trying to locate the splined driveshaft for the oil pump into the bottom of the skew gear. And it’s only when everything seems to line up and you triumphantly wind the Loctited grubscrew into place, that you remember that the gear needs to be fitted and aligned with number one cylinder on the compression stroke, and realise that you have just fitted it 180 degrees out. Or thereabouts: the gear has an odd number of teeth, which means that if you fit it on the exhaust stroke you will not be able to set the injection pump timing within the range allowed by the slotted holes in the pump mounting flange. So you’ll know you have got it wrong at that point.
Timing the injection pump normally requires a special tool that is inserted into the pump drive gear with the crankshaft correctly positioned. The pump is timed at anything between 13 and 16 degrees before top dead centre depending on the age of the engine, and the 2.25 diesel engine has a timing window in the flywheel housing to achieve this, with a pointer that aligns with a scribed mark on the flywheel. Luckily I had an early five-bearing flywheel housing on the shelf: later ones do not have the timing window, although most 2.5 flywheels seem to have the scribed timing marks. The special timing tool is then used to set an adjustable pointer which is bolted to the side cover plate adjacent to the injection pump mounting flange. The tool is removed, the pump fitted and the scribed line on the pump flange aligned with the pointer. If you don’t have the special tool, there are timing marks on the pump rotor that can be viewed by removing the timing window. Instead of the approved special tool I have a dead injection pump with the timing window removed, and this does exactly the same job. This particular engine was missing the timing pointer so I scribed a line on the block in the appropriate place instead.
After the usual struggle to purge all the air out of the fuel system the engine fired up and sounded sweet, but took a fair bit of cranking from cold, misfired off-load at high speed and felt a little bit down on power. I had already suggested to the owner that the injection pump was probably past its best. Having driven the vehicle his comment was that most of the bad habits of the old engine had been carried over to the new one. So the pump has been sent away for overhaul, and will have the fuelling tweaked slightly to optimise it for the slightly larger capacity engine. While waiting for the new pump to arrive I got on with the next oddball.
Another problematic 2.5 engine
This is another naturally aspirated 2.5, this time going in an ex-military One Ten which is to be shipped to the United States later this year. A couple of years ago US Customs started rigorously enforcing the import regulations on old vehicles, and there are now plenty of horror stories about vehicles being turned away at the ports because they have non-original engines.
My American customer had bought a One Ten that had been retrofitted with a 200Tdi: the vehicle had come with a dead 2.5 non-turbo engine in the back, which he dropped off at the workshop in the hope that I could resurrect it. The engine turned out not to be the usual 12J military 2.5, but the rather rarer 11J variant which was fitted to the last few batches of vehicles built for the MOD before the 300Tdi-engined Wolf entered production.
Anyone who has driven a 2.5 non-turbo Defender will know that these vehicles are not especially quick. Military One Tens had a low ratio (1.667) transfer box, which helps a little with acceleration, but a 12J-engined One Ten is still slow enough to be annoying. The US import regulations rule out anything other than a standard 2.5 engine being fitted to the vehicle when it enters the country, but once it has cleared Customs and been registered, engine modifications are no problem. So I looked at the 11J engine that my customer had dropped off, and I looked at the dead 19J turbodiesel that has been sitting in the corner of the workshop for ages, and I had an idea.
The 11J engine is a military-only variant of the 12J, built in fairly small numbers using the turbodiesel block with MODspecified steel liners. I have had a couple of these engines apart before and found that they had the stronger turbodiesel pistons and conrods, although this particular 11J was a service exchange unit and had non-turbo pistons. The crankshaft and camshaft are the same on the 11J/12J and 19J, and the head is also the same although the 19J has sodiumfilled exhaust valves. The 2.5TD has an oil cooler built into the radiator, as do most radio-fitted military vehicles.
So the plan is to build up the 11J with turbodiesel internals and send the vehicle out with a TD injection pump, turbo and manifolds in a box. This will meet US Customs requirements (the vehicle will look 100 per cent standard under the bonnet) and provide an extra 20 or so horses for a couple of hours’ work. The engine is in better shape than I expected, with a perfect, unmarked crankshaft and nice clean bores with the honing marks still visible all the way up.
I will have to raid my stash of parts, as the engine is missing various bits including the flywheel and front pulley. The injection pump has been left with the ports uncovered and is seized solid, and someone has had the valve rocker assembly to bits and lost a couple of rockers. Given how good the wearing parts are, it would be interesting to know what problem the previous owner was trying to solve by partly dismantling the engine. Still, it’s kept me busy!
“You can mix and match components from engines of different types”