Development work for the Federal 3500S prior to the first few cars was done on at least three of the P6B-prototypes; JXC813D, JXC815D, JXC818D, JXC822D and JXC823D. JXC813D was used for developing the air-conditioning system and the new dashboard and switchgear, JXC822D was used as for trim development and electric windows. We believe that it is likely that more cars from the P6B prototype range contributed to the development of the Federal 3500S, as the known cars served more than one purpose. JXC818D was used for clocking up the miles on the North American continent by Rover North America’s project-engineers, whilst JXC813D was also on that trip with personnel from Delaney-Gallay. It seems that the trip went from the Texan heat north towards the Yukon in order to have the cars endure everything that the North American climate could throw at them. JXC815D was used for the trials with detox equipment, sporting the distinct bonnets with 3 functional scoops and JXC823D might have been used for detox equipment trails too, but is known to be fitted out with full interior trim to Federal 3500S specification. A picture of the car exists clearly showing it had some sort of roll-over incident.
Further development work was done on Three Thousand Fives and was likely to be limited to testing the engine which was modified to cope with the Clean Air act, which focused on the limitation of hydrocarbons. An early Three Thousand Five, AXC511F (42500044A) was used for initial trials with Detox equipment. The Detox equipment on the 3500S altered the engine’s carburation and combustion characteristics, as well as providing part-throttle retarding of the ignition and slowing the engine’s response to throttle action. Crankcase emissions were ventilated at the back of the engine and ducted towards the air filter assembly, and evaporative emissions from the engine and the fuel tank were ducted to the elbows just in front of the carburettors, each side being fed by its own charcoal canister. Crash testing was done on multiple car, mainly to cope the US 515 regulations, and although no modifications to the car’s structure were necessary, Rover choose to add side-impact bars.
It seems, judging by the picture archives, that the engine was near to completion by early 1968, with only the power steering being sourced from a different manufacturer. What wasn’t settled at this point was the styling for the North American model. By 1967 David Bache’s Styling Department was looking into a front-end revision for the car, and mock-ups were built with a revised grill and headlamps surrounds. Not unfamiliar for people who knows the New Look models, but still quite different as the grille extended to the leading edge of the bonnet. The bumpers were carried over straight from these mock-ups to production. More cars were built, and full mock-ups were running around by end of 1968, with the engine already to specification.
In June and July 1969 12 early production cars were allocated to the Engineering Department for continental tests and more trials with all these new systems. Testing of the 3500S itself was, it seems, done on the European continent. It’s known that at least two cars were brought to Rovaniemi, Finland for testing under arctic conditions, whilst other cars were part of regular European trips done with multiple cars.
Considering the additional development work done for the 3500S and the late start of the North American model year, production did not begin in earnest until August 1969, and the first deliveries to dealers were in late August and early September at the beginning of the 1970-season.
The dashboard, which predated the launch on other models by 2 years, was first seen as early as 1964 on 169JWD, a styling mock up for the 2000S. It was tested in at least on of the P6B prototypes and consequently in also found its way, albeit in modified form, to the Alvis GTS and P6BS before being used in the 3500S. Rover was one of the first manufacturers to use print-circuit technology, although some gauges are still getting their information externally such as the tachometer and the speedometer. The dial were located behind a concave Perspex surface and although the setup with 5 clocks is similar to the ones found on the New Look models, there are some minor differences. The oil gauge has a red and green zone, opposed to later ones which are plain white, probably because the oil pressure dropped under certain conditions to the red zone - which wasn’t necessarily dangerous - but provoked worries by owners anyway! The closing panel on the side is also left unpainted, and was probably blacked out on New Look models for safety reasons. The switch panel for the headlamps, washer, interior lights and windscreen wiper was also seen before, but again, modified for the 3500S. Earlier versions had the ignition lock incorporated in the switch panel, yet the 3500S had an integrated steering lock. The whole fascia setup has variable brightness green background lighting, and is excellent at night.
Box pleated seats were also a first in a P6, but again, seen before on the Alvis GTS and Graber cars. These were fitted to JXC822D and probably JXC823D although the 3500S had the dubious honour of being the first Rover offered without leather as standard.Instead, Rover used Ambla, which coped must better than the traditional leather with the scorching of the sun in some parts of the USA. Factory Air-conditioning was a first for any Rover, although the factory had officially acknowledged conversion and after market systems from other firms, this was the first time that a system was a factory designed and installed option. It was extensively tested on one of the P6B-prototypes in the USA. That car was actually built up by Delaney-Gallay themselves, and used a system which already debuted in the contemporary Jensen Interceptor. It utilizes vacuum control as variable temperature control, a feature which was, and still is very modern. The air-conditioning systems available on the 2000s and P5s were retrofitted and not fully integrated in the design of the car. The draw-back from the air-conditioning system is that it made the engine bay even more cramped than in already was. On a Three Thousand Five there was space for the air to circulate in the engine bay, but apart from the optional air conditioning, on the 3500S Rover was already forced to add two charcoal canisters, an extra brake fluid reservoir for the dual-line braking system, the power steering system and with the air-conditioning added to that there was not much room left, which consequently lead to overheating. Therefore the Rover engineers deemed in necessary to design three scoops. The inner being used as ram-air for the revised air cleaner, and the outer pair is used to force more air into the engine bay, directly above the carburettors. These featured flaps, which can be manually opened and closed depending on the ambient temperature. However, the scoops were also add to the appeal of the V8 engined P6, opposed to the, by North American standards, rather slow four-cylinder models. However, vapour lock remained a problem and Rover added an electrical fuel pump and a fuel return line to maintain a continuous flow of fuel when idling through dense traffic in high temperatures. Conveniently this also made space for the vertical mounted air conditioning compressor.
The power steering was deemed a luxury item, but the dual line braking system was forced upon Rover by US legislation and was never to be in the specification. Peter Wilks, then Technical Director, was once quoted in saying that dual line brakes were inherently unsafe, as he reasoned that having no braking was more controlled than having two-wheel braking which might cause a car to invert and consequently roll over. Therefore, Rover opted to mirror the system; one line for nearside front- and the offside rear wheel, and the other for the offside front- and nearside rear wheel. Another luxury item at the time was the Automatic Enrichment Device (or AED), which eliminated the need for manual choking by means of a bi-metal which closed the cut-off valve when exhaust temperatures rose. Although not a first for the 3500S, as it was first introduced in 1968 on the P5B Coupe and the Three Thousand Five, Rover and SU never got it right. However, the manual choke conversion offered for these cars as a dealer fitment never became available for the 3500S, so many owners either removed them or by-passed the system. Only recently has a redesign of the system cured the problems that plagued the 3500S so much during its production life, and caused a lot of bad press for the car. It would either choke or it wouldn’t, but if it did, it wouldn’t stop.
Another first for any Rover was the fitment of electric windows, which was tested on two cars. The first was a 1963 P6 pre-production car registered 102FJJ. It’s not clear when she received the electric windows, but it features a bank of rocker switches above the radio where on the 3500S the main air-conditioning vent is situated. The other car fitted with the system is JXC822D, and the system is similar to 102’s. Eventually Rover opted for AC Delco window motors and switch gear from the contemporary GM range. Unfortunately they had to fully redesign the window frames.
Rover marketed the 3500S as a luxury sedan, rather than a sports saloon which would’ve been more in line with the 2000TC. However, even Rover engineers described the Three Thousand Five as a ‘V8 Automatic with 2000TC Manual’ performance and therefore they were aimed at the luxury market. Rover also trimmed the car accordingly, but with very little domestic competition in the same price bracket the 3500S was destined to compete with other cars over a relatively small portion of the market, its main competitors were expected to be Volvo and Mercedes-Benz. Rover hoped of course that the car would also compete with the Buick/Chrysler segment, and the car certainly outdid those cars in terms of standard equipment and reception by the American motoring press was good. They unanimously agreed that the interior was a nice place to be, despite Ambla being the standard fitment and the rear seats not be overly capacious. ©