Service Bay
The life and times of the engine which was developed for the avant garde Rover p6.
Inside the four-cylinder engine which provided the power for the innovative and still popular Rover P6.
I t’sa mystery why the Rover P6 has taken so long to climb in value when it was so highly regarded for so long. Perhaps it’s the high survival rate compared to others, but either way, the 2000 has been around forever as a decent useable classic car.
The Rover 2000 engine was a pretty sophisticated bit of kit for 1963, and whilst it lacked the smoothness of the six-cylinder Triumph 2000 engine, power outputs of 90 bhp at 5000 rpm for the 2000 and 114 bhp at 5500 rpm for the twin carburettor TC were very good for the era - torque was 126 lbf.ft at 3500 rpm. Launched in late 1963 and winning the first ever Car of the Year trophy in 1964, the 2000 was intended to be a standalone model but Rover were always going to develop a higher performance twin carburettor version – this was launched in 1966 for export markets only but by late that year, Rover relented and launched the 114 bhp TC model in the UK.
Basis of the 2000 engine is a cast iron block with 85.7 mm bores and supports for a five bearing crank. The crank was a forged steel item (no cast iron here) with a stroke of 85.7 mm also, making this engine completely ‘square’ with a capacity of 1978cc. Up top was a cast alloy crossflow cylinder head with a single overhead camshaft that runs in five bearings and which is driven by a Reynolds two stage duplex timing chain. The SC (single carb) version had part of the inlet manifold cast into the head - in essence, there is still a removable manifold but the cam sits so far to the left that there are very long inlet ports, all of which help the 2000 engine develop excellent torque.
To aid quality control (this is before BL don’t forget), the iron block had detachable steel side covers so that the quality of the block castings around the waterways could be monitored. The timing chain is tensioned by hydraulic tensioners and the TC versions have double valve springs and all 2000 engines had a flat cylinder head and pistons with both deep dishes and generous valve cut outs. Pistons varied from the SC to the TC with compression ratios of 9:1 for the SC and 10:1 for the TC that famously required the use of five star fuel.
Sturdy connecting rods are used, made from EN16 steel and which have horizontally cut big end caps that are secured by high tensile studs with nuts - another mark of a quality engine when most mass produced stuff used bolts with steel lock tabs.
The finishing touch was a smooth cast alloy cam cover secured by three nuts that act on
three studs integral with bearing caps 1, 3 and 5. Likewise, the sump is cast alloy as well whilst the distributor runs off the auxiliary shaft. Fuelling was taken care of by an SU HD8 carburettor on standard cars, and twin SU HS8 carbs on the TC version.
Designed from scratch with no parts taken from the P4 or P5, the new P6 engine was a superb thing built to high standards and capable of a long life.
For 1973, the 2000 was replaced by a new 2200 model, both as an SC and a TC. The extra capacity of 2205 cc was achieved by enlarging the bore to 90.5 mm whilst the crankshaft stroke remained as before. Power was about the same as before and the 2200 majored on torque rather than a power increase - the SC developed 93 bhp at 5000 rpm on a 9:1 compression ratio,and 126 ft.lb at 2500 rpm whilst the twin carburettor 2200 TC developed 115 bhp at 5000 rpm, and gave 135 ft.lb of torque at 3000 rpm on a compression ratio of 9:1 also - by the this time the carburettors being used were of the new HIF (horizontal integral float) type, the SU HIF6.
In production until March 1977 when P6 production finally ended, the P6 engine was built for 14 years yet didn’t see service in other Rover products.
The 2000 and 2200 were effectively replaced by the SD1 2300 and 2600 cars that appeared six months after P6 production ended, but they were blighted with reliability problems and never gained the reputation built up by the four cylinder P6.
FIVE CYLINDERS, A DECADE BEFORE AUDI
In 1964, a year after the 2000 launch, Spen King along with Gordon Ashford, Jack Swaine and Bryan Silvester as well as Mike Lewis and Erin Branson looked into a six cylinder version of the 2000’s engine to be made on the same tooling as the four. However, the 2000 engine was already fairly heavy for a four and a straight six version was just too long and too heavy. So five cylinders became a compromise idea and the first blocks were made simply by cutting up two 2000 blocks: one had only cylinder cut off the front and the other was cut in half with the two sections being sent to Barimar to be specially cast iron welded together before being machined. At four inches longer than the four cylinder and 100 lb heavier, the new 2500 engine was a production reality and it could be fitted into a standard 2000 body without modification. Whilst two complete engines were built and tested, Rover was still some way away from getting the engine to run smoothly enough. With four-cylinder engines, a power
stroke occurs every 720 degrees, or every two turns of the crank and there its no overlap between power strokes. Straight six engines are in virtually perfect balance and pistons move in pairs with cylinder 1 mirroring number 6, 2 mirroring 5 and 3 mirroring 4. On a straight five though one piston in effect is the odd man out and there are always large overlaps in power cycles and that’s what gives a straight five its distinctive ‘thrum’.
Rover engineers got over a lot of this by experimenting with engine mounting positions and also attaching the engine mounts at the engine’s centre of gravity - Rover took out a patent in 1972 (1293135) but this was long after the whole idea of a five-pot engine had been dropped. There’s no doubt the 2500 five cylinder engine would have been a success because it was developed by very clever engineers and built by Rover when things were made properly.
However, the fly in the ointment was the purchase by Rover of the rights to build the all alloy V8 and suddenly there was just no need for the 2500 engine. Of the two that were built, one is known to exist still, an interesting look into what might have been.
STRENGTHS AND WEAKNESSES
The Rover 2000/2200 engine is one of those units that has an indefinite lifespan - if it’s serviced on the dot with good oil, it will just plod on until it wears out and there are very few, if any, real weakspots. One problem is that the pressed steel side covers on the block can rust through and weep coolant, and if that is left unchecked overheating can result. Failure to use the correct 50/50 water and anti-freeze mix can cause corrosion of the alloy head and that will require welding so a good used head is a better idea if you can find a good one. Timing chains can rattle a little on start up as well as a weird ‘ringing’ noise at just over 1000 rpm. That’s not a problem as such but replacing both the upper and lower timing chains is quite a big job although the top one isn’t too bad. Worn out SU carbs on the TC models are common now and worn spindles result in air leaks that can cause idle problems. The 2000 TC cars with the 10:1 compression need Super Unleaded with a lead replacement additive. A strange tinkling noise heard from within the inlet manifold on TC cars will possibly be an errant carburettor to inlet manifold adaptor, and you need to remove the manifold and fish this out before if gets where it shouldn’t.
But that’s pretty much it – such was the design of the unit and the quality build that there really are very few problems.