430bhp tuned 1987 BMW 635CSi Turbo E24

While, at first glance, this might appear to be a fairly standard E24 6 Series, a closer look reveals that all is not as it seems, and this unassuming classic is hiding some big secrets behind its iconic sharknose bodywork…

Words: Elizabeth de Latour

Photos: Gregory Owain

Shark Tale

This E24 635CSi was deemed too rotten for restoration, so it’s been transformed into a stripped-out, turbocharged track machine, and it’s a blast.

The 6 Series family has a long legacy, starting in the 1970s, and has given us some stunning cars. It’s such a shame, then, that this once great model went out with such a whimper in the shape of the G32 6 Series Gran Turismo, which looked nothing like the sleek coupés that had come before, and more like a bloated 5 Series. It’s a sad end to what was once a great GT, effortlessly combining luxury and performance in a stylish package, but the 6 Series gained a lot of fans over the years and generations, and thanks to them, we can enjoy cars like the one that started it all, the E24. We love to see people caring for and preserving these classics, just like the example we’ve got here. But, hold on, something’s not quite right. Is that a towing strap? A stud kit? Is that a… roll-cage? We have questions – several questions – and Fred Marsh- Allen (@e24turboshark) is the man to answer them…

“I had owned an E28 525e, E21 323i and various other older BMWs, but not an E24. This one was up for £3500, and it was a manual with Buffalo sports hide and an LSD. It was a no-brainer!”

As we chat with the handyman, things seem pretty innocuous, and Fred had a similar sort of BMW experience growing up as many of us did that shaped our motoring lives and turned us into the BMW fans we are today. “I’ve liked BMWs since I was 16, and I had to choose a car for my mum from a used car dealer forecourt; it was a 1992 E36 325i (those early M50 E36s sound great),” he tells us, and from that point on he had his sights set on one day owning a BMW himself. “My first car was an E36 318ti, and I bought it because it was the easiest way into a 16-valve four-pot BMW at the time,” he explains. “A year later, I bought an R reg E39 540i Touring, which was a spaceship in comparison. I should have kept that, for it was mint, and it fell off the DVLA database about two years afterwards,” he laments.

Fred’s also owned an E34 540i and currently owns an E60 530i alongside his 6 Series, so he’s clearly got broad BMW taste and good taste, at that, but what led him to buy an E24? “I had owned an E28 525e, E21 323i and various other older BMWs, but not an E24. This one was up for £3500, and it was a manual with Buffalo sports hide and an LSD. It was a no-brainer!” he exclaims. “It was in Guildford.

It looked tidy enough in the metal but had a respray at some point, although some of the trim hadn’t been removed. It drove very nicely and had just under 180,000 miles on it,” and so a purchase was made, and Fred did initially have a plan in mind.

“I planned to keep it as a light project – do the bushes and suspension, refresh the ignition and cooling system etc.,” says Fred, “but I decided to give it a half-decent paint job. When it was in the body shop, we found it was very (very) rotten and needed a huge amount of welding,” he grimaces. “There was filler everywhere (even on the roof). It was at this point I decided to turn it into a track car,” so all was not lost, and the unexpected E24 transformation began.

With the plan being to take this 6 Series on track, the rather old and soft standard suspension needed some serious upgrades, so Fred’s first port of call was sorting the chassis. “BC Racing coilovers were chosen for the suspension as there wasn’t a great deal else available at the time, with Ireland Engineering adjustable ARBs (again, all that was available),” but that combination was already enough to transform how the big Six drove, massively reducing body roll, stiffening everything up, sharpening the handling and getting the E24 sitting lower, too, which is always a nice bonus.

“The original ‘Hydroboost’ combined power steering and braking system was deleted, along with the ABS, and an E34 vacuum servo was made to fit.

E34 540i brakes with Ferodo D2500 pads were fitted along with HEL braided Lines and RBF600 fluid. The car now has a 3.64 final drive with Racing Diffs 60% locking clutch setup, and the diff and ARB mounts have additional bracing to the chassis/ body of the car,” explains Fred.

“Finally, there’s a custom-made half-cage, which was made using an E36 Coupé cage roll-bar,” and that rounds off an impressive selection of upgrades that ensure this 6 Series is fighting fit and ready for the track.

Naturally, a track car needs some sticky rubber, and you need some dedicated wheels, so Fred has a couple of sets to choose from. “The wheels shown are the Remotec 16” road wheels, and for the track, it has BBS RC090 Style 5 17s with R888R tyres,” which is a great combo both in terms of visuals and on-track performance. Fred has just also picked up a set of Compomotive TH17s for track use, which are very cool, and will give the big Six a proper track car look.

While everything we’ve looked at so far is great, the most exciting part of this build is what you’ll find under the bonnet; some serious work has gone into the engine, and it’s delivered some serious results. “This has been quite a long project,” says Fred. “I initially bought a load of bits a friend had cobbled together to turbo his E32 – they were an absolute bargain, and I just bought them as I knew they’d be easy to sell on. However, a very talented friend of mine, Steven Crooks (who I first discovered through owning my E12 528 – he was the only person I could find who would touch the Solex 4A1 carb), knowing I’d had the parts for some time, asked me if I ‘had turbo’d that E24 yet?’ I joked that I hadn’t, but he was welcome to do it all for me. He responded with ‘OK then,’ and so began four years of scrabbling about on his driveway,” Fred laughs.

“The engine is the original M30B34 bottom end but with a M30B35 head, as they have slightly larger inlet valves and flow better; new stock-spec camshaft and rockers, a Cometic MLS head gasket and an enlarged plenum, which took Steve 10 hours to mill from a block of aluminium. The plenum has a ‘flipped’ inlet, with air now entering from the nearside, and a Turbosmart fuel pressure regulator covers the hole where the throttle body once mounted. There is a custom-made fuel rail, Siemens 875cc injectors, and a 3” intercooler with custom aluminium intake pipework and airbox. We did a distributor delete/Bremi coil pack setup, and the car is running an Emerald K3 ECU with a custom engine loom and Magnecor high-temp ignition leads in a custom aluminium shroud. The turbo is a Pulsar GTX3584RS item (the previous turbo blew up on the dyno), with a Turbosmart ProGate50 wastegate, a Kangaroos Team exhaust manifold, a custom downpipe into 4” exhaust (it was sideexit, but another silencer was needed for track). There’s also an Accusump oil accumulator, an E32 coolant expansion tank, and a K64 twin-plate clutch for the original Getrag five-speed manual gearbox,” and that’s an incredibly comprehensive list of engine upgrades. M30s can easily handle some boost, albeit with a helping hand, and Fred’s example is definitely delivering the goods, with 430hp and 460lb ft of torque on tap, and that’s a lot in what is now a lightweight car.

That’s because Fred embarked on a comprehensive weight reduction programme across his Six. “The car has 90% of all the external trim removed, which saved approximately 14kg, and also an Xmoor Motorsport front bumper, DTM mirrors (the originals fell apart), and a Ford Capri Mk2 rear boot spoiler,” which has kept things subtle, but with a little touch of individuality, and we love the turbo script on the boot lid. “The interior is completely stripped, with custom-made panels for the gauges, Foamex door cards, the battery has been relocated to behind passenger seat, which is also where the Accusump sits,” Fred explains, and he’s not kidding when he says the interior has been stripped. The carpets are gone, the sound deadening is done, there’s a lightweight Corbeau bucket seat for the driver, and combined with the exterior weight savings, this 6 Series now tips the scales at just 1320kg, which is impressive stuff for what was once a luxury sports GT.

When you think 6 Series, you don’t think dedicated track car, but we love to see builds that subvert expectations. Fred’s E24 does exactly that, and this is the result of a lot of hard work and dedication. He’s owned his 6 Series since 2017, and it took six years to get it to where it is now and it was time very well spent because what a fantastic machine this is. Opting for a track car build was certainly not on Fred’s to-do list when he bought it, it’s far better to see a rusty E24 6 Series turned into a stripped-out turbocharged bruiser than broken for parts or sold to a scrapyard. And while this is already a full-on build, Fred’s got a few more mods up his sleeve: “I’m planning to make the cage a full cage, upgrade the intercooler, as it’s currently restricting the power, fit some posh bucket seats, and do a sunroof delete,” and that will give it less weight, more power, and that means even more fun – what’s not to like?

Turning his E24 into a track build was not Fred’s original plan for the car, but he’s built himself a belter of a 6 Series. Innovate AFR gauge.

TECHNICAL DATA Turbo E24 635CSi

• ENGINE AND TRANSMISSION: 3.4-litre straight-six M30B34, M30B35 head, Cometic MLS head gasket, custom-milled enlarged aluminium plenum with flipped air inlet, Turbosmart fuel pressure regulator, custom-made fuel rail, Siemens 875cc injectors, 3” intercooler with custom aluminium intake pipework and airbox, distributor delete, Bremi coil packs, Magnecor high-temperature ignition leads in custom aluminium shroud, Pulsar GTX3584RS turbo, Funk Motorsport turbo blanket, Turbosmart ProGate50 wastegate, Kangaroos Team exhaust manifold, custom downpipe into 4” exhaust, Accusump oil accumulator, E32 coolant expansion tank, Emerald K3 ECU, custom engine loom. Original Getrag 265/6 overdrive five-speed manual gearbox, K64 twin-plate clutch, 3.64 final drive with Racing Diffs 60% lock clutch setup
• MAX POWER: 430hp
• MAX TORQUE: 460lb ft
• CHASSIS: Road: Remotec 8x16” (front) and 9x16” (rear) wheels with 225/50 (front) and 245/45 (rear) tyres, track: 8x17” (front and rear) BBS RC090 Style 5 two-piece wheels with 235/40 (front and rear) tyres, BC Racing coilovers, Ireland Engineering adjustable anti-roll bars, diff and ARB mounts with additional bracing to chassis/body, Hydroboost power steering and braking system delete, ABS delete, E34 vacuum servo, E34 540i brakes, Ferodo DS2500 pads, HEL braided lines, RBF600 fluid,
• EXTERIOR: Original Opal green, Xmoor Motorsport front bumper, DTM mirrors, Mk2 Ford Capri rear boot spoiler, turbo boot script, most exterior trim removed, 1320kg weight
• INTERIOR: Completely stripped, Corbeau driver’s bucket seat, Takata harnesses, custom-made panel for oil pressure, oil temperature, boost and water temperature gauges, Innovate AFR gauge, Autometer Sport Comp Monster rev counter, Foamex door cards, battery relocated behind passenger seat, Accusump oil accumulator, Clubsport weighted gear knob, custom-made half-cage
• THANKS Steven Crooks, Lorna Crooks, Jerry the dog, and all at Emerald

Custom-mounted gauges allow Fred to monitor the engine’s vitals. This 6 Series looks fairly innocuous on the outside, but it has plenty of secrets up its sleeves. The turbocharged M30 produces a very healthy 430hp.