If there’s one thing we at Retropower know, it’s how to build a flawless ’80s Opel – we’ve turned our efforts to several of Russelheim’s finest over the years, meaning we’re well placed to tackle blitz-badged projects of all kinds. Case in point, the latest Manta to pass through our hands, a project distinct from every other Opel build we’ve yet taken on by dint of its odd choice of engine – a Rover V8.

We’re not suggesting that Rover’s eponymous ex-Buick lump is rare, not when it was the engine of choice for pretty much every British sports or kit car for the best part of half a century, but it isn’t the kind of motor you expect to find between the wings of a Manta, much less one due to have a complete 400 kit. It’s the kind of swap that’s likely to have Manta purists up in arms, but there can be no doubting its old school appeal.

Not that actually fitting the engine was anywhere near the forefront of our minds when the time came to actually begin work on the shell. The customary Retropower media blasting session revealed more rot than we’d anticipated finding, which in turn ensured that we dedicated a considerable amount of time and effort evicting all traces of rust.

The owner also requested we carry out a programme of drivetrain upgrades, starting with the axle. Undeterred by the knowledge that nothing from Opel’s own parts bit was going to be up to the task at hand, Nat and Callum began investigating alternatives from other manufacturers. Their search was rewarded however, the pair settling upon the Dana axle from, of all things, a Volvo 740 Estate! It must easily rank as one of the odder axle swaps in Retropower history. Said axle was paired with a True Track LSD sourced from the USA, and the resulting setup will doubtless be capable of handling the power & torque the ubiquitous V8 sends its way.

Even with the Volvo axle in situ (a trickier task than you might imagine), we were still faced with a dilemma, namely how best to mount it within the shell and the confines of the Manta rear suspension. We eventually called upon our experience building Curt Pattinson’s Ascona 400 replica, which is why the Manta now boasts trailing arms based on those found on the Opel Commodore C, with OE mounts where they met the shell and custom versions where the bolt to the axle.

It’s a similar story with the suspension, with SuperPro bushes found throughout, uprated front dampers and springs, plus custom poundage springs at the rear. As ever with a build of this kind, each and every under-body suspension, chassis and drivetrain component has been blasted, zinc metal sprayed and powder coated.

The owner stipulated that while he wanted the Manta to look like a special stage tamer but be wholly suited for use on the public roads on a daily basis, which presented us with something of a problem when it came to re-fit the interior. The work carried out to fit the Volvo axle had served to rob us of vital interior space, which presented us with as problem when the time came to re-fit the rear bench, and in the end we were forced to fabricate custom ‘short link boxes’, just shallow enough so that an equally custom rear bench can sit atop them. We can’t promise the result will be as comfy as when the car first left the line, but it’s a seat nonetheless.

Other elements of the car will be more conventional, the Manta’s appearance for one. There are very few tasks more pointless than trying to improve on the appearance of the Manta 400, which is why we’ve decided to go down this time tested route with this build, despite it having a distinctly un-400 like engine. The whole car will eventually sport a coat of Porsche Metallic Silver, plus the requisite 400 graphics pack.

Again, there’s no getting around the fact that the Rover V8 is a left field choice for a 400-kitted Manta, but the work we’ve invested should ensure that it handles like a go-kart – check back for more updates.

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