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
|8.13 cr||240nm @ 2400||SD1 AU,USA, Swiss|
|9.35 cr||280nm @ 2600||SD1 Europa|
|9.75 cr||285nm @ 4000||SD1 Vitesse|
|8.13 cr||285nm @ 3250||Range Rover|
|9.35 cr||312nm @ 2600||Range Rover|
|8.90 cr||340nm @ 3250||Range Rover|
|9.00 cr||421nm @ 2500||Leyland P76|
|8.90 cr||375nm @ 3250||Range Rover|
|9.34 cr||395nm @ 3250||Range Rover|
|9.00 cr||465nm @ 2400||Buick 300 2 barrel|
|11.0 cr||502nm @ 3000||Buick 300 4 barrel|
|9.00 cr||510nm @ 2400||Buick 340 2 barrel|
|11.0 cr||547nm @ 2800||Buick 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.
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
|Capacity||Power||Rpm||Comp ratio||Used in|
|3.5 litre||155 hp||5250||9.35:1 CR||SD1 (standard)|
|3.5 litre||194 hp||5250||9.75:1 CR||SD1 Vitesse|
|3.9 litre||132 hp||5000||8.13:1 CR||Range Rover|
|4.2 litre||202 hp||5000||8.90:1 CR||Range Rover|
|4.4 litre||192 hp||4250||9.10:1 CR||Leyland P76|
|4.6 litre||225 hp||5250||9.35:1 CR||Range Rover|
|4.9 litre||210 hp||4600||9.10:1 CR||Buick 300 2 Barrel|
|4.9 litre||250 hp||4800||11.0:1 CR||Buick 300 4 barrel|
|5.6 litre||220 hp||4000||9.10:1 CR||Buick 340 2 barrel|
|5.6 litre||260 hp||4000||11.0:1 CR||Buick 340 4 barrel|
a Buick 340 V8 in a Rover SD1
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 Car||Capacity||Power||rpm||Average piston pressure|
|Rover SD1||3.5 litre||155||5250||7,4 bar|
|Range Rover||3.9 litre||173||5250||7,4 bar|
|Range Rover||4.2 litre||186||5250||7,4 bar|
|Range Rover||4.6 litre||204||5250||7,4 bar|
|Buick 300||4.9 litre||210||5250||7,4 bar|
|TVR||5.0 litre||222||5250||7,4 bar|
|Buick 340||5.6 litre||235||5250||7,4 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
|Capacity||Power||rpm||Average piston pressure|
|3.5 litre||190||5250||9,4 bar|
|3.9 litre||210||5250||9,4 bar|
|4.2 litre||228||5250||9,4 bar|
|4.6 litre||250||5250||9,4 bar|
|4.9 litre||263||5250||9,4 bar|
|5.0 litre||270||5250||9,4 bar|
|5.6 litre||291||5250||9,4 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
|Capacity||Power||rpm||pressure / CR||Used in|
|3.5 litre||190 hp||5250||CR 9.75:1||350i Wedge series|
|4.0 litre||240 hp||5750||CR 10.5:1||V8S|
|4.3 litre||280 hp||5500||CR 9.8:1||Chimaera|
|5.0 litre||340 hp||5500||CR 10:1||Griffith|
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!
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.
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
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.
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.
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
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)
Calculating the flexibility of various engines can give some interesting results. Here are some examples.
|SD1 3500 V8 ||2,70|
|TVR Chimaera 4.6||1,35|
|TVR Chimaera 5.0||1,28|
|Lotus Elise 111S||1,80|
|Ferrari 360 4.5||1,51|
|VW Golf 1.9 TDI||2,96|
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!