Rover 3500 V8
A new kind of Roving
Rover 2000 was designed from the outset as a four-cylinder car of around
2-litres, the possibility of increasing both power and refinement by the use of
a large unit with more cylinders was contemplated from a fairly early stage in
the development period. At one time, six cylinders were envisaged, but when
development work began on the light-alloy V8 now used in the Rover 3.5 litre,
this became a natural choice. With the design of the 2000 so new throughout,
however, resources were concentrated in the first place in getting the basic,
four-cylinder car into production. The result, as everyone knows, was the most
successful car produced by Rover to date and further consideration of a
bigger-engined version was inevitably shelved until production of the normal
2000 (and the subsequent TC and Automatic versions) could be matched to demand.
Now the time
has come for the 3 1/2-litre V8 engine to be wedded to the basic 2000 conception
and the result is the new Three Thousand Five. This car, it should be stressed,
is in addition to the Rover 2000 which is likely to continue as Roverīs best
seller, with a production figure currently running at around 800 per week. The
new model will appeal mainly to buyers who want the now well-known handling and
handiness of the Rover 2000, plus the extra refinement and performance given by
the light-alloy V8 engine. Just what this means in terms of performance will be
found in the road test report. Here, to put the story in perspective, it is
necessary only to say that a maximum speed of 117 mph was recorded together with
a 0-50 mph acceleration figure of 7 seconds and a touring fuel consumption of
Mating the V8
engine to the 2000 was not the simple exercise it might appear. Most of us have
had experience of cars in which the alternative-engine plan was not an
unqualified success simply because the car was designed for one unit in the
first place, and little was done to tune its characteristics to suit the new
one. This certainly does not apply to the Rover Three Thousand Five, although
the initial instructions to the engineering department were to "make minimum
alterations". The ideas of Rover engineers on acceptable standards meant that
"minimum" was interpreted very freely and a great deal of development work was,
in fact, carried out to achieve results which would satisfy them.
To the engine
itself very little has had to be done and almost all of it for installation
convenience. To be specific, the exhaust manifold now has a centre outlet
instead of a rear down pipe in order to clear the modified 2000 hull, the
external oil filter has been reangled to clear the front cross-member; the air
cleaner is now of round instead of oval section, the power steering pump with
its belt drive has been omitted as power assistance is not required, and the
alternator now has a finger quant for safety - a feature which has also been
adopted on the Rover 3.5-litre.
In all other
respects, the very successful 90-degree V8 engine is unchanged. Notable features
include cylinder blocks and crankcase formed in a single light-alloy sand
casting, into which dry cylinder liners are pressed; die-cast light-alloy
cylinder heads with inclined in-line valves operated by push by push rods and
rockers from a single central camshaft; self-adjusting hydraulic tappets and
rockers of light-alloy with sintered iron inserts for the push and sockets and
steel inserts in the valve stem pads; wedge-shaped combustion chambers; and
pistons with shallow depressions in their crowns to give both a beneficial
effect on the quench area and a ready means of varying the compression ratio to
suit particular markets.
How the V8
engine was installed in the hull is a minor development story in itself. As the
unit would not "drop in" as it stood, the obvious course was to extend the nose
of the car. This was tried but had three disadvantages: overall length was
increased, new wing and bonnet pressings would have been needed, and there was
too much forward weight. Next, two cars were built on a "cut-and-shut" basis,
existing structures being cut about and welded up to accept the new engine with
a minimum of alteration. These two cars were proved useful for development work
but despite the obvious advantage of a "mini-mod" policy, much more was thought
very careful rearrangement enabled the engine to be installed with no increase
in overall car length, no undue front axle weight (the V8 engine weighs the same
as the "four" within a few pounds) and without any need for new bonnet or
front-wing pressings. This arrangement involved moving the battery to the boot
(where it is neatly recessed into the floor in a light but very strong box of
expanded, high-denaty polyethylene), moving the front cross member forward (but
not so much that the grille would have been pushed beyond the bonnet nose) and
tilting the engine back 3 degrees 54 minute to enable the starter to clear the
propeller shaft tunnel. The effect of the engine tilt on the action of the
universals is greatly reduced by correctly phasing the universals and suitably
aligning the final drive assembly so that minor variations in prop-shaft speed
are largely cancelled out.
bonnet pressing is unchanged, its stiffeners have had to be modified to avoid
fouling the front cross member, the headlamp apertures have had to be placed
nearer the ends of the extruded grille, and various detail modifications made to
inner wing pressings, engine mountings and so on.
considerable work had to be done on the cooling system. Obviously, greater heat
dissipation was needed and a desired radiator area of about 360 sq.in. was
obtained by installing a cross-flow radiator of 20 in. wide and 18 in. deep.
Because this extends well below bumper level, a stout protection channel is
bolted below it to prevent accidental damage. The radiator incorporates
oil-cooling tubes in its side "header tank" for the Borg Warner automatic
transmission, and its location is such that there is room for a condenser in
front of it when this is required for air conditioning.
radiator capacity was considered adequate, troubles were experienced with the
engine getting too hot and the car heater not hot enough. This apparently
contradictory state was eventually traced to the fact that the low position of
the filler cap made it impossible to bleed the system completely. Although the
circulation was vigorous enough to clear the air pocket, the result was to
aerate the water with small bubbles and introduce problems of heat transference.
One the trouble had been located, it was easily cured by connecting a bleed pipe
from the inlet manifold water jacket (where the air accumulated to the filler
cap side of the radiator tank, thus enabling the offending air to be expelled by
running the engine up to normal temperature with the filler cap removed.
Air locks in
the fuel system are not uncommon with big engines under small bonnets and this
has been forestalled by a spill-return system. A bleed hole at the second
carburetter is connected back to the tank reserve outlet so that cool fuel from
the enlarged (15-gallon) tank is always circulating when the engine is running.
other engine modification is a redesigned exhaust system employing double-skin
pipes for noise suppression wherever possible. The two pipes from the manifolds
meet behind the engine and a single pipe then leads to a modified forward
silencer, beyond which the system is identical with that of the 2000 except for
the tail pipe where an increase of only 1/8 in. (to 1.7/8in. o.d.) has been
found to give a power increase of slightly over 1 bhp.
In unit with
the engine is a Borg Warner Type 35 automatic transmission with D1 and D2
positions, as on the big Rover, except that the maximum shift speed from
intermediate to top has been lowered from a nominal 4.600 rpm to 4.200 rpm,
while clutch pressures have been modified to improve shift quality. The internal
gearbox ratios are unchanged but, as one would expect, the final drive ratio has
been raised compared with the 2000 to take advantage of the much higher power
(47% over the TC) and torque. The change is from 3.54:1 to 3.08:1.
differential is used to cope with the added loading and advantage has been taken
of the need for a new and larger final drive casing to reposition the filler
more accessibly. The mountings of the differential casing are of the same
design, but stiffer material is used for the flexible bushes because there is no
need to cater for the secondary out-of-balance forces present with a
general layout and principles of the final drive/rear suspension assembly follow
the 2000 design and the drive shafts, hubs, de Dion tube, Panhard rod and rear
differential carrier are interchangeable, there are considerable differences in
the remainder of the system. One of the most important is the use of a new front
cross member. On the 2000, a short cross member carrying the nose of the
differential case extension is bolted to the propeller shaft tunnel. On the new
design, the cross member is considerably extended so that it picks up on rubber
mountings on the body sills which are less susceptible to noise transmissions.
In addition, the forward ends of the bottom suspension links are now flexibly
mounted on the cross member instead of on the body. The new arrangement
considerably reduces both road and transmission noise.
with the same end in view include larger rear bushes for the top links of the
Watt linkage; there are styrene butadiene rubber which gives slightly more
damping than natural rubber. The result is to increase compliance at the top
link, and the bottom link bushes are correspondingly stiffened to restore the
have been increased from 230 lb./in. to 265 lb./in. and new telescopic dampers
of 1.3/8 in. bore are used in place of the 1 in. size. They also have improved
rubber and polyurethane mountings top and bottom. At the front, the bottom links
have been modified to clear the engine and the suspension has also been
stiffened slightly - with spring rates up from 150 lb./in. to 170 lb./in. at the
spring - and the leak settings on the dampers adjusted to give more control.
With a view to improving directional stability, castor has been increased from
3/4 degree to 1 1/2 degree (plus or minus 1/2 degree).
would normally have stiffened the steering slightly and accordingly a minor
change has been made in the steering ratio. With the new Burman recirculating
ball unit used, the ratio in the straight-ahead position is now 21.5:1 compared
with 20.3:1 - and more on full lock.
As one would
expect, the added performance has brought some brake changes in its train and
the diameter of the front Girling discs have been increased from 10.312 in. to
10.82 in. At the rear, the disc diameter is the same, but it is worth noting
that (as on the 2000 now) the inboard brakes are of the Girling swinging caliper
type with integral handbrake. Increased servo assistance is provided by a
Lockhead unit of 8-in. effective diameter in place of the 7-in. type, giving a
boost ratio of 4:1.
development work went into the choice of wheels and tyres, including many miles
of high speed tests on Italian autostrada. Investigations were concentrated on
175 and 185 normal sizes and 190 low-profile tyres. Eventually, the 185 section
was chosen as providing an ample safety margin, although one tyre manufacturer
would have been quite happy for the smaller section to be used. An additional
factor taken into consideration, was that when the car comes to be exported - it
is a home-market model only ar present - the 185 size will comply with German
called for a 5 1/2-in. rim and it was decided to fit the latest safety-ledge
rims which give greater security against loss in pressure when drastic cornering
distorts the walls. New wheel trims with a new claw fixing are used.
The change in
tyre sizes introduced clearance problems for all-weather covers at the rear and
this has been overcome by using wheels with a different offset to reduce the
track by 3/8 in. on each side. Obviously, use of these wheels at the front would
reduce the track there too and curtail steering lock. The front hubs have,
accordingly, been modified to restore the position.
Of the body,
there is little to say here because it is identical with that of the 2000 and,
in any case, its features are the subject of comment in the road test. The only
differences in equipment are the use of improved pedal rubbers and the fitting
of a 140 mph speedometer. Yet mechanically, the apparently simple job of
installing an alternative engine into an otherwise highly satisfactory car has
involved the surprising number of changes detailed in this report. Just how the
mixture works in practive will be found in our road test - in which, too, the
detailed specification of the car will be found.
Motor / UK