The Sunbeam Rapier fastback is well worth sharpening up, says one-time owner Mark Dixon.
It could have and should have been a Capri rival, but the Sunbeam Rapier Fastback never enjoyed anything like the sales success of the flashy Ford. For all its striking pillarless coupe looks, a Rapier is sure a rare animal these days that few enthusiasts even think to put it on their shortlist of classic buys. That`s a shame, because the fastback Rapier (which is basically a Hillman Hunter in a party frock) is a remarkably usuable and characterful everyday car.
Undoubtedly, the Rapiers biggest failing was the galloping body rot that claimed most of the 46,000 cars built. The good news is that mechanically these cars are tough and simple, being based on the Hunter estate floorpan. The Hunter legacy - narrow track, leaf-sprung rear suspension - means there`s considerable room for improvement and yet suprisingly few owners seem to have bothered trying. Here are a few suggestions that might inspire some creative tinkering.
Performance was never a problem for either the Rapier or its Holbay-tuned spin-off, the H120. Both cars can crack the ton, and the old-fashoned torque of their 1725cc engines means they are quick off the mark. In fact, if everyday usability is what you need, a bog-standard Rapier with the factory twin Strombergs is still a good all-rounder.
If you`re hungry for more (or you already own an H120), then you will need to bore out the block, and possibly change the cam and carbs. As an example of what`s possible, the car in our pictures has been bored out to 1900cc and runs forged Volvo P1800 pistons. The camshaft is a Jeff Howe 300-degree product giving 0.335in lift, and the carbs are Weber 45DCOEs. Cylinder head is the original Holbay, flowed and ported out by Oselli Engineering, with Rover SD1 2300 inlet valves turned down to a head diameter of 1.6in - exaust valves are the stock Holbay items. Flywheel, crank and conrods have all been lightened and balanced.
These changes were developed on a trail-and-error basis by owner Howard Johnson, who estimates they`ve raised the power output from the standard H120`s 95bhp to around 140-150bhp.
The existing radiator should be up to the job, but you could add an electric fan between grille and radiator for extra reassurance in heavy traffic. Before taking this step, consider having the radiator recored. Modern cores are inherently more efficient and specialists such as Serck Marston can build in extra cooling capacity on demand. Howard Jonhson claims that if you have a tuned engine it`s worthwhile swapping the standard 82-degree thermostat for one that opens at 74 degrees. This allows coolant to flow from the engine to radiator at a lower temperature.
The standard four-speed gearbox is a lovely unit with a notibly light `change, and is quite capable of dealing with the extra power from even highly tuned engines. However, overdrives sometimes slip: one solution is to shim the pressure relief valve to increase internal oil pressure slightly.
You`re spoilt for choice when it comes to choosing a final drive ratio. Standard Rapiers (and the Hunter estate) had a 4.22:1 back axle, but the H120 used a 3.89:1 for more relaxed high-spped cruising, while automatics had 3.70:1. The last mentioned has been fitted to our feature car, since its 1.9-litre engine makes it more than capable of pulling the tall gearing.
You shouldn`t need to change anything for road use, since the standard front disc/rear drum set up works well enough. It has even been known to cope with cars converted to Rover V8 power. If you intend driving particularly hard, then competition disc pads are an idea - Howard Johnson uses MGB pads made by Mintex.
Probably the Rapier`s weakest link, its suspension was lifted directly from the Hunter saloon with virtually no modification. The H120 gained slightly stiffer front springs, but was otherwise similar to the Rapier: both models have a tendancy to pitch into corners and unersteer determinedly when cornered hard.
Nobody seems to have experimented much with suspension tweaks in recent years, though a Rapier was rallied with some success by Gordon Jarvis in the late 1970s. He found that uprating the front springs by 20 per cent gave the car exellent handling on forest stages. Front struts were reconditioned by Armstrong (no longer possible) while Bilstein competition dampers from the Mk II Escort were used at the rear.
Spax used to make adjustable damper inserts for the front struts, but are no longer interested unless you care to order vast quantities. It`s the same story with the rears, although Demon Tweeks tell us they still have some Spax rear adjustables in stock at £37 each. The part number is 350.
One simple mod favoured by Howard Johnson is to lower the rear ride height, which helps body roll, by inserting lowering blocks between rear axel and springs. About one to one and a half inches is ideal, he says.
Rapier steering is not as sharp as the car`s name suggests, but it`s not bad considering it uses the good old Burman recirculating ball. An ingenious improvement used by Gordan Jarvis on his rally car was to replace the steering idler with a left-hand-drive steering box, minus innards, to transmit steering input more acurately. But first you`ll have to find a left-hand-drive Rapier...
In theory, it`s possible to convert a Rapier to rack-and-pinion, using the rack and steering column from an Avenger, but retaining the Hunter track rod ends. It`s been done on a Hunter, although no-one to our knowledge has yet tried this conversion on a Rapier.
The ordinary Rapier had 155x13 tyres as standard equipment, while the H120 was given slightly wider 165x13s, but 175-section rubber will bring an improvement in grip for either model without loading up steering excessively. It`s pushing it to squeeze 185s on the standard rims, however.
Howard Johnson has disovered that Ford Cortina Mk II 1600E rims can be used in conjuction with spacers between wheels and hub, and although he experienced some problems with tyres fouling the wheelarches, he reckons the car handled well - possibly because of the wider track. Clearly there`s scope for some lateral thinking here. A safe option is a set of Minilite-style alloys, which look very good on these cars.
Making a Rapier go faster in a straight line is relatively easy. Making it quicker round corners is more of a challange, and is a concept that has yet to be fully explored. Who`s going to be the first to come up with a really rapid Rapier?