Rover's Vikingship V8 Tuning.....Incrasing capacity. Rover's Vikingship

There is no subsitute for cubic inches. A bigger engine simply means more power because it burns more air and fuel in the same time than a smaller engine. The big advantage of the Rover V8 is that you can increase the capacity of an existing engine or get another larger Rover engine with the same dimensions and mountings without much increase in weight...

There are not only 3,5 litre Rover/Buick engines around but also 3,9/4,2/4,6/4.9/5.0 and even 5,6 litre versions!

The bore, stroke and torque of the various V8 engines are
Capacity Bore Stroke Comp Ratio Torque/rpm Used in
3.528 l
215 cu.in.
3.50
(88.9 mm)
2.80
(71.1 mm)
8.13 cr240nm @ 2400SD1 AU,USA, Swiss
3.528 l
215 cu.in.
3.50
(88.9 mm)
2.80
(71.1 mm)
9.35 cr280nm @ 2600SD1 Europa
3.528 l
215 cu.in.
3.50
(88.9 mm)
2.80
(71.1 mm)
9.75 cr285nm @ 4000SD1 Vitesse
3.947 l
240 cu.in.
3.70
(94.0 mm)
2.80
(71.1 mm)
8.13 cr285nm @ 3250Range Rover
3.947 l
240 cu.in.
3.70
(94.0 mm)
2.80
(71.1 mm)
9.35 cr312nm @ 2600Range Rover
4.275 l
260 cu.in.
3.70
(94.0 mm)
3.03
(77.0 mm)
8.90 cr340nm @ 3250Range Rover
4.414 l
270 cu.in.
3.50
(88.9 mm)
3.50
(88.9 mm)
9.00 cr421nm @ 2500Leyland P76
4.554 l
277 cu.in.
3.70
(94.0 mm)
3.22
(82.0 mm)
8.90 cr375nm @ 3250Range Rover
4.554 l
277 cu.in.
3.70
(94.0 mm)
3.22
(82.0 mm)
9.34 cr395nm @ 3250Range Rover
4.997 l
300 cu.in.
3.75
(95.2 mm)
3.40
(86.4 mm)
9.00 cr465nm @ 2400Buick 300 2 barrel
4.997 l
300 cu.in.
3.75
(95.2 mm)
3.40
(86.4 mm)
11.0 cr502nm @ 3000Buick 300 4 barrel
5.650 l
340 cu.in.
3.75
(95.2 mm)
3.85
(98.0 mm)
9.00 cr510nm @ 2400Buick 340 2 barrel
5.650 l
340 cu.in.
3.75
(95.2 mm)
3.85
(98.0 mm)
11.0 cr547nm @ 2800Buick 340 4 barrel

When the stroke is longer than the bore we have a long stroke engine (Buick 300 and Buick 340).
The P76 is called a square engine with the bore and stroke being equal. As a rule of thumb the bigger the bore in relation to the stroke the more willing the engine is to rev. If it's low end torque you want, go for a longer stroke.

P76 Engine 19,6 kB

So what power can be had from a larger capacity engine? We have to start somewhere so here are some power quotings for standard 3.5 litre Rover engines and the average pressure (bar) on the piston that go with that particular engine.

Capacity, Power, Rpm, and Compression Ratio for some Rover engines
CapacityPowerRpmComp ratioUsed in
3.5 litre155 hp52509.35:1 CRSD1 (standard)
3.5 litre194 hp52509.75:1 CRSD1 Vitesse
3.9 litre132 hp50008.13:1 CRRange Rover
4.2 litre202 hp50008.90:1 CRRange Rover
4.4 litre192 hp42509.10:1 CRLeyland P76
4.6 litre225 hp52509.35:1 CRRange Rover
4.9 litre210 hp46009.10:1 CRBuick 300 2 Barrel
4.9 litre250 hp480011.0:1 CRBuick 300 4 barrel
5.6 litre220 hp40009.10:1 CRBuick 340 2 barrel
5.6 litre260 hp400011.0:1 CRBuick 340 4 barrel

a Buick 340 V8 in a Rover SD1
Engine development 1950-1985 7,5 kB

The average pressure in the cylinder is dependend on:

  • compression ratio, higher compression means higher average cylinder pressure
  • camshaft profile, long duration and/or high lift cams give higher cylinder pressure
  • Inlet resistance, the lower the inlet resistance the more air enters the engine giving higher pressure
  • Outlet resistance, lower outlet resistance also allows air to enter more quickly
  • Combustion effiency, a good location of the plug and good flame travel let's all the air/fuel burn giving high pressure

Let's take the average pressure of the standard SD1 engine (7,4 bar). Now we increase the capacity of the engine while keeping the average pressure on the piston constant at 5250 rpm. Let's see what power we can expect of those big engines.

Expected Power of a Rover engine with increasing capacity at 7,4 bar and 5250 rpm
Type of CarCapacityPowerrpmAverage piston pressure
Rover SD13.5 litre15552507,4 bar
Range Rover3.9 litre17352507,4 bar
Range Rover4.2 litre18652507,4 bar
Range Rover4.6 litre20452507,4 bar
Buick 3004.9 litre21052507,4 bar
TVR5.0 litre22252507,4 bar
Buick 3405.6 litre23552507,4 bar

Now 4.6 litre with 204 bhp. It is a lot of power but not impressively so. Let's increase the average pressure on the piston to 9,4 bar as is the case in a Vitesse engine.

Expected Power of a Rover engine with increasing capacity at 9,4 bar and 5250 rpm
CapacityPowerrpmAverage piston pressure
3.5 litre19052509,4 bar
3.9 litre21052509,4 bar
4.2 litre22852509,4 bar
4.6 litre25052509,4 bar
4.9 litre26352509,4 bar
5.0 litre27052509,4 bar
5.6 litre29152509,4 bar

Well these figures are more like it! By improving the breathing of the larger engines to Vitesse standard we can get the higher average pressure of 9,4 bar and thus more power. Companies like TVR are easily extracting even more power from the larger size engines, as the next figures show:

Power for some Rover/TVR tuned engines
CapacityPowerrpmpressure / CRUsed in
3.5 litre190 hp5250CR 9.75:1350i Wedge series
4.0 litre240 hp5750CR 10.5:1V8S
4.3 litre280 hp5500CR 9.8:1Chimaera
5.0 litre340 hp5500CR 10:1Griffith

Now 340 bhp from 5.0 litre is remarkable! certainly if you take into account that we're still talking about an engine with only two valves per cylinder and not even equipped with an overhead camshaft! The Griffith will just give every Porsche a run for his money!

TVR Griffith 7,6 kB

What we see is that fitting a bigger engine with standard heads, camshaft and carbs will see some power increases. Going to uprate a standard engine to Vitesse spec's with it's improved breathing will spice up things considerably and going even further like TVR with a different camshaft and some extra attention to the heads and inlet will make a real powerhouse!

So when thinking of putting in a bigger engine in your SD1 remember that it's not just the engine. But also the inlet and outlet system that needs attention to get real power! A bigger engine at the same speed needs a lot more air than a smaller engine. For instance the 4.6 litre needs 30% more air at the same engine speed than the standard 3.5 litre. This means that the inlet, valves,etc. also need to flow 30% more air.

The larger air requirement also explains the relatively big increases in power which can be achieved by using uprated stage-1 or stage-2 cylinderheads with larger valves and a sharper cam on the big engines. The advantages of a flowed head are bigger with a large capacity engine than with a smaller one.

Lotus Elise 12,0 kB
Light weight and the screaming Rover K-series VVC engine makes the Lotus Elise 111S one of the worlds best sports cars

A bigger engine needs more air and fuel. The needed amount of air and fuel is linear with the engine size at the same speed. Double the engine size and you will need twice the amount of air and fuel (and get roughly double the power). But if you use the same inlet system the double amount of air will lead to a larger drop in pressure which is not linear but increases with a power of two!. This means you will get less than twice the power you expected.

Increasing from 3.5 litre to 4.0 litre will give an increase in the needed amount of air by 30% but if you do nothing in the inlet system the pressure drop will be 1.3^2 = 1,69 Thus a 70% increase! This will mean you will not be able to get the full performance of your engine!

At lower speeds the engine will be breathing ok but the larger engine will soon run out of breath at higher rpm. This non-linear effect makes it so important to also carefully select your inlet configuration when going to a bigger engine.

Thanks to: Adriaan Briene


The P76

Well it's not one of the world's best looking car's but what it does have is one of the nicest engines! The Australian built Leyland P76 had a 4.4 litre version of the Rover engine.

The car in the pictures was owned by Henk Bruurs.

The Australian P76  7,8 kB The Australian P76 9,3 kB

From Short to Long stroke

Almost every Rover engine is a short stroke engine. This means the diameter of the bore is bigger than the stroke of the crankshaft. Only with the P76 with a bore and stroke of 88.9 mm and the Buick 300 with a bore of 95.25 mm and stroke of 86.36 mm and th buick 340 with a bore of 95.25 mm and stroke of 97.80 mm did the SD1 come close to a long stroke engine

The aluminium V8 was designed by Buick as a short stroke engine right from the start. This was quite modern as in those days most engines were long stroke engines. The graph on the left shows that from the beginning of the fifties towards the start of the eighties engines became more and more short stroke engines. Only in the last decade can we see a return of longer stroke designs because it is easier for those engines to meet the emission regulations and they are better suited to run on lower octane fuel.

Further interesting things we can see in the diagram is the steadily increasing hp/litre ratio with a dive in the seventies because of emission regulations. The eighties see a recovery of the hp/litre ratio because of the increasing use of fuel injection. With the increase of the hp/litre ratio the speed at which maximum torque and power is achieved also moves up.


The Buick 340 engine
A Buick 340 V8

3.9 or 4.0 litre

What is the difference between a 3.9 or 4.0 litre engine? Both have a bore of 94.0 mm and a stroke of 71.1 mm. There is no difference in capacity at all!

The real differences are:

  • The 3.9 has the provisions like the 4.0/4.6 litre for the crossbolts but they have not been drilled.
  • The 3.9 has the smaller main journals from the 3.5 The 4.0 version has the same journals as the 4.6 litre. The 4.0 crank also has a longer nose.
  • The 3.9 has the concentric oil pump but coupled with standard distributor the 4.0 has a distributorless system and thus no hole for a distributor.
  • 4.0 uses longer rods, lighter and shorter pistons
  • The 3.9 has the 14CUX 'hotwire' fuel injection. The 4.0 has the Lucas 'GEMS' engine management system.


Engine flexibility

If you increase the size of the engine in your car, this will not only improve power but also increase the flexibility of your engine. This means it pulls better at low rpm's and has a wider power band. Off course when you give this larger engine a hotter cam you will lose part of the gained flexibility

It is possible to calculate engine flexibility with the following formula:

(max. torque*max. rpm)
--------------------------------
(torque at max. power* rpm at max torque)


Max. power kW rpm min
Max torque Nm rpm min
Torque at max. power(Nm):
Engine rpm
Engine flexibility

Calculating the flexibility of various engines can give some interesting results. Here are some examples.

CarEngine flexibility
SD1 3500 V8 2,70
Rover Vitesse1,53
TVR Chimaera 4.61,35
TVR Chimaera 5.01,28
Porsche 911SC1,27
Lotus Elise 111S1,80
Ferrari 360 4.51,51
VW Golf 1.9 TDI2,96

With a flexibility ratio of 2,70 the standard V8 set-up can be compared with the VW turbo diesel. And it's true the 3500 is a great car for towing a caravan! The Vitesse scores quite low with 1,53 and as we all know has to be revved more than a standard SD1 to get good performance.

The bigger tuned TVR's score even lower than the Vitesse and also the 1984 Porsche 911SC scores low in engine flexibility. But then these engines all have 2-valves per cylinder. The Lotus Elise with the highly tuned Rover VVC K-series 4-valve engine is already a lot better. And the Ferrari with it's 4-valve V-8 also is quite good for its respectable state of tuning.

It is clear, low tuned engines have more flexibility. But give a tuned engine a 4-valve head and it can be made quite flexible too. A turbo or supercharger can also make a big difference, see the Golf Diesel!

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© rwp nov. 2005