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Rolls-Royce/Bentley V8

Rolls-Royce/Bentley V8 Published: 18th Feb 2016 - 0 Comments - Be the first, contribute now!

Rolls-Royce/Bentley V8
Rolls-Royce/Bentley V8
Rolls-Royce/Bentley V8
Rolls-Royce/Bentley V8
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Want to give your first class travel a speedier service? Here’s how to pep up your V8-powered Rolls or Bentley, from Shadows to Mulsanne Turbos!

You expect Rolls-Royces and Bentleys to glide along in serenity and silence and for the majority of owners that’s exactly how they like them! However, there’s also a group who, while content with their Crewe classics, would prefer a slightly less stuffy and more satisfying drive when the mood takes them. Surprise, surprise, there’s not a lot of tuning parts around for Rollers and Bentleys and yet there’s quite a bit you can do to improve your model, by using later Rolls and Bentley parts meaning you are not unduly affecting originality at the same time. Here’s our tips.

BEFORE YOU START

Most cars will have been looked after pretty well and apart from rusty rear suspension spring pans, all should be well and up for uprating. But before you do, you need to do the sums carefully to see if it’s worthwhile.

For example, if you yearn for the thrills of a Mulsanne Turbo then you’re better off buying one instead of trying to make your more mundane Mulsanne (or Silver Spirit) perform like one because any tuning exercise will prove expensive, plus you may find it hard to sell a tuned car because it’s not how most owners want their high class carriages to be.

However, improving the suspension and brakes, using factory components is not a bad move at all and subtle gains are welcomed from all quarters including owners’ clubs.

Genuine factory parts aren’t cheap, naturally, but plenty of specialists also deal in good second-hand and reconditioned lines and – due to the relative ease of interchanging components from a later model – it can prove to be a quite cost effective method, especially if certain bits on your car are worn and need replacing.

Before embarking, speak to an independent R-R expert and the excellent Rolls-Royce Enthusiasts’ Club as well as the Bentley Drivers’ Club. Most of the changes outlined can be carried out at home on your drive with normal tools.

HOTTING ONE UP

It should come as no surprise to learn that tuning parts for that V8 are more than thin on the ground despite this overhead valve engine dating back almost 60 years! Apart from owner apathy, the other reason can be put down to the superb basic engineering that’s hard to better although, occasionally Crewe’s finest did appear in motorsport, such as the 1970 World Cup Rally.

Rolls and Bentley specialists, Phantom Motor Cars of Surrey, built a mighty 700bhp Mulsanne Turbo for club racing and promotional work so there’s certainly some scope for improvement if you want it. That said, Phantom wisely warns that performance tuning Crewe’s classics is both difficult and expensive.

Originally, the 6.2-litre yielded around 200bhp which was virtually doubled in the case of the 6.7-litre Mulsanne Turbo engine (Rolls was always coy on releasing official power figures) as fitted to the Continental. Thus the most logical ‘tweak’ is to fit later, larger engines as the factory did over the years and perhaps add the Mulsanne turbocharger. It’s more difficult to fit under the bonnet of a Shadow, yet Rolls did with the Corniche S.

Start off with a general rolling road check using a dynometer to fine tune the ignition settings and the SU carbs’ mixture settings, which may involve different needle jets and springs. And fit a good electronic ignition with quality ignition leads if the engine is not already so equipped. The Camargue spin-off used Solex carbs for a touch more power but they are hideously expensive for the gains on offer.

Having a tuning company modify the cylinder heads by improving their gas-flow and raising the 9.0:1 compression ratio is another good ploy because this V8 doesn’t rev very high (the rev counter was red-lined at just 4500rpm, even on the first Turbo model) meaning that a racier camshaft does little good. In fact, Rolls experts Harvey Bailey at one time produced a modified camshaft but it didn’t prove popular, although we understand hotter camshafts are still available in the United States from various companies.

Bear in mind that as these cars are automatics only, raising the rev limit will alter the transmission’s characteristics and optimum gear ‘change up’ points but a transmission specialist can alter this to suit if need be. Phantom fitted a GM 400 three-speed Pursuit gearbox uprated with Kevlar bands, re-valving plus heavy-duty clutches and a strengthened torque converter but you’re looking at some £3500 for a similar gearbox. While we hear it has been done, we don’t know of a conventional manual gearbox conversion on the market. Instead, a Hurst manual self-shifter can be adapted to give a ‘semi auto’ facility – speak to Phantom about this as it uses such a set up on its racer to good effect.

The block relies on replaceable cylinder liners which not only simplifies rebores but also means there’s potential to overbore the engine. Almost seven full fat litres has been extracted from the Rolls V8 but it’s very expensive, very difficult (due to liner and piston availability) and hardly worth the hassle.

The carb-fed Turbo is the easiest to fit because later models using fuel injection involve wiring mods and installation of the ECU. It yields a useful 324bhp and some 400lbft of torque so if you want more then it’s relatively easy to increase the boost pressure to achieve astronomical horse power. Happily, Phantom says its racing Mulsanne relied upon a standard engine without the need for any strengthening, despite achieving 700bhp.

In the States, some tuning emporiums have replaced our British V8 with an American one and there’s no shortage of those – GM units being the most popular picks.

RUNNING GEAR

This is the area owners concentrate most on and where the most gains can be found. Tightening the soft suspension is the first step and this can either be done using factory parts from later and sportier versions (ie Turbo, Turbo R dampers and springs) or fitting the established Harvey Bailey suspension kit. This modification is well known in Rolls circles and, costing over £1500, comprises of carefully selected spring, dampers, thicker anti-roll bars and harder bushes. If that’s too rich, replacing individual components, such as dampers can be done; Boge or Koni shock absorbers come recommended, for example and this mod alone may be all you require.

The ultimate is probably Bentley’s own specification taken from the Turbo R (the letter stands for ‘Roadholding’), although bear in mind that later post 1990’s Silver Spirits and Mulsannes featured an active ride system at the rear; Phantom Motor Cars disconnected it on its racer and had special springs made to compensate but there’s no need to do this on road cars.

More effective are thicker anti-roll bars plus you can opt for lowered springs but the ride will suffer. Simply overhauling the active system and fitting new dampers costs under £500 per side and may also improve things enough on their own. There’s an awful lot of suspension bushes employed to isolate the running gear from the first class travelling compartments and these deteriorate like any other car. Turbo suspension bushes certainly sharpen the ‘feel’ of the car but speak to an aftermarket supplier such as Polybush, Super Pro and Power Flex for best advice first on the other options on offer from the more limited selection of factory components.

Costs? Phantom lists the improvements like so (prices are approximate) Mulliner anti-roll bars front and rear (40 per cent stiffer) £1600+, special stiffer lowered (50 mm lower) front coil springs £900, and lowered rear (50mm) coil springs at £800. In addition, anti-roll bars that are 40 per cent stiffer cost in the region of £1600.

The rack and pinion steering fitted to the Shadow II is a great improvement but grafting it on an earlier car is impractical. Later models, it can be further improved by grafting on the Continental R set up but – you guessed it – the swap is costly, unless your car needs a new rack anyway.

The brakes can do with uprating as even the Turbo stopped on Shadow items, including the pads. Various upgrades are available (start with EBC Greenstuff pads), including the approved Alcon upgrade but the pads alone cost £800.

A more sensible bet is to fit late Turbo R and Continental anchors but first of all ensure that the hydraulic system is in top order; it needs a proper overhaul every eight years and while it costs some £2000 for a specialist to do, is money well spent.



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