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Opel Kadett GSi 16V Superboss: Import only

The Opel Kadett Superboss is one of the many great homologation specials to come out of South Africa. Here's why it's so special

If the word Superboss was plastered across the back of a burbling American, ‘60s, muscle car – the sort that rocks menacingly as its big block V8 engine tries to shake itself free – you’d probably consider the name a touch over the top. An Opel Kadett, the Vauxhall Astra here in the UK, called Superboss. Surely a joke?

The Superboss was a South African only evolution of the Kadett GSi 16V, of which a mere 244 were made. The standard GSi 16V (known as the Big Boss in SA) was as ‘80s hot hatches go, a quick car. This is largely thanks to the excellent 20XE engine - General Motors’ 2.0-litre 16V, four-cylinder engine, which benefitted from a Cosworth designed cylinder head. The 20XE, or as it's more commonly named in the UK ‘Red Top’, bestowed the Kadett with an impressive 156bhp - 26bhp more than a 1.9 205 GTI and 17 more than the heavier 16v Golf GTi.

Cosworth head, forged pistons, sodium filled valves, stainless steel tubular exhaust manifold and nitrated camshafts made the Red Top extremely tuneable and a very popular race engine. All GSi 16Vs had the fantastic Red Top, but the Superboss took it a step further…

Compression was increased to 10.5:1, the inlet diameter was increased and given a K&N air filter. Aggressive 276 degree cams made by Schrick were fitted with 'race' timing, although 'street' timing could be specced if you wanted to compromise peak power for a smoother idle – no thanks! Promotec remapped the ECU and increased the rev limit to 7000rpm (from 6800) to really make the most of those hot cams.

Delta Motor Corp, which was entrusted by GM to assemble the South African cars, including the Superboss, claim that ‘up to’ half of the Superboss heads were hand ported by Cosworth. As there were no actual numbers given to how many heads were touched by the magicians at Cosworth, I think that can be taken with a pinch of salt. Hand-ported by Keith Duckworth or not, the Superboss produced a much more impressive 167bhp.

If the engine mods have got you interested, then the changes made to the rest of the car should be just as exciting. The arches had to be rolled to accommodate new 7-inch wide, lightweight wheels made by Aluette that sit even closer to the body thanks to -20mm Irmscher springs.

Stripping out the sound deadening, air conditioning, power steering, electric windows and removing the opening mechanism from the rear windows entirely, helped to reduce weight. The front fog lights were removed, which saved weight, but more importantly the holed were then used to duct air towards the vented front brakes.

In many ways, the Superboss paved the way for the hardcore, front wheel drive hot hatches such as the Mini GP, Megane R26.R and Trophy R. What the Superboss also has in common with those other hot hatch legends is a limited slip differential. Now a fairly common thing in a performance front wheel drive car, in the ‘80s it was incredibly rare to find an LSD on a production car even one as special as the Superboss. The diff was coupled to a lower ratio final drive too, 3.55:1 from the standard GSi's 3.42:1.

The Superboss was as unrefined as it was quick. Hastily put together by Delta Motor Corp, the lack of sound deadening only seemed to amplify every squeak and rattle – of which there were reportedly many. This is despite Delta's manager of quality assurance Rolf Mentzel’s huge input.

While other hot hatches of the late ‘80s were a riot of lift off oversteer, the standard GSi was resolutely understeer biased. The Superboss was said to be an effective set-up, thanks to its LSD and lower springs, but a 205 GTI or Renault 5 GT Turbo would have been much more lively.

But who cares, really? The odd squeak and rattle here, and lack of oversteer there. None of that detracts from how special the Superboss is. All the changes that elevated the GSi 16v into the Superboss weren't done just because they were cool, or to justify the name. The Superboss was a homologation special, built to win races.

Despite battling with the bigger engined, 2.7-litre BMW 325is in the South African Group N Touring Car Championship, the boisterous Opel was extremely competitive. Although being down in capacity the Superboss's low weight, considerably powerful engine and an 80 per cent locking differential (rather than the road going Superboss which could only lock up to 18 per cent) kept the BMWs honest.

In the hands of Michael Briggs the Superboss was near unbeatable, and won the championship three years running. A recalcitrant, uncompromised road car with race winning pedigree, the Superboss has all the attributes that makes homologation cars so incredibly desirable.

Words: Will Beaumont // Images: Nazir Sibda

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