Engine swapping has long been a popular pastime for German tuning companies. Those who do it the best can run the gauntlet of the stringent TUV type approval process, and those deemed good enough to pass are granted the holy grail of manufacturer status, permitting them to replace the OEM VIN plate with one of their own. 

It's how the likes of Alpina, AMG, Brabus and Ruf got their start. Hartge was perhaps one of the more famous outfits to perform heart transplants on BMWs, but sadly the Beckingen-based concern liquidated in 2019. Into the breach has stepped Manhart. 

Founded in 1986 by Manhart brothers, Wilfried and Günther, the company initially focused on repairing and maintaining BMWs out of the back of the family's petrol station. However, they soon began to develop their own modifications for BMWs before specialising in developing prototypes for AC Schnitzer, Hamann Motorsport and Hartge. What’s not well known is Hartge subcontracted Manhart to build perhaps their most famous car of all, the H50 - an E46 M3 powered by the S62 5.0L V8 from the E39 M5.

Which leads us nicely to the car seen before us. Given the firm’s previous experience with the E39 M5’s running gear, the V8 was the obvious powerplant to return to harvesting. And it's that sublime engine which now rests within the nose of the 850i pictured. 

The result of a three-year-long project, it’s out with the V12, and in with the V8. Initially, that might seem like a downgrade, but ditching the twelve-cylinder motor from a luxury limousine for a fire-breathing M division unit, mated to its manual six-speed transmission will certainly help this restomod fulfil the potential of the painfully handsome E31 shape - a car that has long cried out for some proper M mojo.

Previously the 850i made do with 296 bhp and 332 lb-ft of torque courtesy of the V12, labouring through a four-speed auto. Now, thanks to some very mild tuning and a stainless steel exhaust, the M5 lump knocks out 420 bhp. With a similar kerb weight to the E39 five series, we can at least expect the performance of the MH8 to match that of the M5, with 0-62 mph taking less than five seconds and the potential to hit 186 mph.  

The V8 also aligns with Manhart’s mission to turn the grand tourer into more of a bonafide sportscar, or in Manhart’s words “something which would have adequately filled the role of an M8 at the time.” To support this, H&R springs have been mated to Bilstein B6 dampers, and the rest of the chassis has been overhauled too, with all axle parts blasted and refurbished and all rubbers and bearings renewed. 

Reigning-in the mighty engine are 4-piston fixed callipers clamping 340 millimetre, perforated brake discs. The new brakes are hidden behind eye-catching Manhart Concave One alloy wheels measuring 9×20 and 10.5×20 inches, which are shod with Continental Sport Contact 7 tyres (255/30fr and 295/25r). Small spacers also help the new alloys fill out the wheel arches, ensuring a flush fit to the wings.

Previous Manhart builds have been best suited to extroverts, but flashy alloys aside, the restomod touches to the MH8’s exterior have been kept very subtle. The sporting credentials are underlined by the presence of the beefier front skirt and rear skirt of the 850 CSi, plus the iconic double-spar M wing mirrors. There’s also a subtle lip spoiler on the boot. 

The restraint gives the MH8 a classy appearance and the car is all the better for it. After all, why mess with one of BMW's most timeless designs? Personally, we’d go for a fractionally smaller alloy with a fatter sidewall, perhaps an updated “throwing star” or M parallel design with a deep dish, but it's not a deal breaker. 

The theme continues inside, with a period-sensitive re-trim of the seats complete with a flash of the M-tricolours in the manner of the E36 M3. The rear 2+2 seating, door panels as well as the dashboard and centre console have also received new leather and now feature coloured applications and stitching. There are Alcantara highlights for all the drivers' touch points such as the steering wheel, gear knob and handbrake, and the headlining, side pillars and seat backs have also been trimmed from the material. 

As depicted by the cars’ name, just five MH8s will be produced, the first of which is currently for sale at €149,000, or just under £128,000 at current exchange rates. Given the appreciating value of the E31 Eight series, plus the need for a donor engine and hardware, it's not an extortionate figure for a nut and bolt restoration which includes a full respray. If you like the idea of using those pop-up headlights to flash autobahn traffic out of the way, contact Manhart here.