Frequently Asked Questions
THERE are a few questions which I am asked time and time again. I don’t mind people contacting me for advice, although it can be a little annoying when I am trying to do something really fiddly like aligning the timing gear on a two and a quarter petrol engine, and the phone rings for the fifth time in a hour: “Hello mate, saw you on the internet and I wondered if I could just pick your brains for a minute…” Email is better for that sort of enquiry. So I thought I’d deal with a few of the more common queries via this column, starting with the old favourite – does my Series have a three- or five-bearing engine?
Back in 1957 when the plans for all-new Land Rover petrol and diesel engines were drawn up, most four-cylinder engines had just three bearings supporting the crankshaft. Traffic speeds were low and there was no expectation that the new engines would be run at high speeds for long periods. The bearings were amply dimensioned by 1950s British motor industry standards and the three-bearing engines did excellent service.
But as traffic speeds increased and the motorway network expanded, three bearings started to look like too few. The problem was a tendency for the long, heavy crankshaft to try to flex at high speed which wore out the centre bearing in particular, making the engines rough and rattly. The diesels, despite running at lower speeds, were starting to earn a reputation for breaking crankshafts when worked hard. Something had to be done.
That ‘something’ was the introduction in 1980 of a new cylinder block and crankshaft, now with five main bearings rather than three. The troublesome rear crankshaft seal was redesigned and the flywheel bolts beefed up. The top half of the engine was unchanged. Five-bearing Series engines are without doubt smoother and more durable than three-bearing ones: the two types of engine are fully interchangeable, and I suspect that most surviving Series vehicles will have had at least one engine change by now. The age of the vehicle is not a reliable guide to the type of engine fitted. So how do you tell the two types apart?
One way is to check the serial number which is stamped on the left side of the block just behind the outer edge of the water pump. There is a list of serial numbers on my website (glencoyne.co.uk/ engno.htm). But not all engines have a serial number: on factory rebuilt units the original number was removed and replaced with a stamped brass plate which tells you precisely nothing about the engine. There is, however, a simpler way to tell the difference.
Look at the left-hand side of the engine block below the manifolds. Five-bearing blocks had reinforcing ribs cast into them, including a distinctive large X shape near the alternator. X marks the spot: if your engine has these ribs it is definitely a five-bearing engine. If it has no ribs it is without doubt a three-bearing lump. There are no exceptions.