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Hillclimb Hero

Dissecting Australia's fastest hillclimb racer...

Words by Michael Knowling, Pix by Julian Edgar and RD Images

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A 450hp+ supercharged VW flat-four cocooned in a carbon fibre body with an all-up weight of 420kg? Work those figures and you'll find a power/weight ratio of over 1000hp per tonne! Maybe that's one reason that this is without doubt the best of the best amongst the current crop of Australian hillclimb vehicles.

Owned by Peter Gumley of NSW, this beastie has claimed the last four consecutive Australian hillclimb championships. That comes as no surprise when you take into account the 2.6 second 0-100 km/h performance, the beautiful race suspension, carbon fibre aero package and - of course - Peter's fair share of driving ability. Peter picked up his dak-dak powered SCV racer in 1994. A bloke by the name of Jack Wortmeyer (we think that's how it's spelt!) had built the vehicle back in around 1970 and - to the best of Peter's knowledge - it's the only one in existence.

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The triangulated chassis is made from conventional ERW steel tube, and the suspension hung from each end is custom fabricated. Up front there's Triumph Spitfire uprights and you'll find Brabham ex-Formula 1 magnesium uprights on the rear. All pivots are rose jointed.

Since taking up ownership, however, Peter has relocated a few critical pick-up mounts and therefore altered the dynamic suspension geometry. Spax dampers had also been fitted to the car when Peter bought it, but he's since moved to Bilsteins. Interestingly, the spring rates are comparatively soft - linear rate 310lb on the front and about 255lb on the rear. Note, however, the springs are laid over on an angle, altering the 'effective' spring rate.

Front and rear swaybars are adjustable for maximum track-to-track handling flexibility.

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Motorvation for Peter's racer is an air-cooled, 2-litre Volkswagen Kombi flat-four - its low centre of gravity makes it a popular choice in hill climb events. This one, however, now displaces just over 2.3-litres due to custom oversized barrels - the standard 71mm crankshaft stroke remains and the barrel diameter is now 102mm.

The static compression ratio works out to around 7.5:1 thanks to a set of Chev-type Venolia forged pistons. Interestingly, just one standard Kombi rod has failed over Peter's 6 years of competition with the car - and it may have already been cracked when the engine had last been rebuilt. Pretty good going for a stock rod, specially when you remember how much power the engine's making!

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Maintaining the essential supply of lubrication is a fabricated 3-stage dry sump arrangement driven off the end of the camshaft. The VW air cooling system is retained, because - as Peter says of water cooling systems - "If you don't need it why take it with you?" Hillclimb events generally aren't long enough to cause overheating, he adds.

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The twin cylinder heads are extensively modified Kombi 2-valve units. A US-sourced cam (a fairly mild 'supercharged' grind), Chev-style Gene Berg valve springs and very large valves round out the top-ends. Engine airflow is controlled via a 3 3/16-inch bell-mouthed throttle body, which was pulled from a Formula 1 boat! A foam air filter is incorporated into the engine cover.

Peter tells us he used to run an old Roots-style Marshal cabin pressure blower on the motor, but when he missed at gear at an event a few years ago it got blown into pieces. No problem, though, a guy in crowd came up and offered the use of his twin-screw Whipple blower for the event! Peter ended up buying it from him and - after fabricating new manifolds incorporating a built-in blow-off valve on one side - he says it's much more efficient. He runs a lot less boost now but still makes more power - about 18 psi gives over 450 horsepower (estimated).

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The exhaust system is Peter's own fabrication, with the guys from Vari-Flow Technology currently making up a tuned length system. At present, however, each head breathes into 1 3/8-inch primaries and 2?-inch main pipes. These merge into a 3-inch barrel that's surprisingly capable of toning down the VW's bark.

Firing the necessary amount of fuel into each cylinder is a mechanical Hilborn injection system. Fuel is injected into each port by an Enderlie methanol injector, whereas it'd been previously put in through the top of the cabin pressure blower. This injector relocation picked up horsepower, response, and it also reduced stress on the blower (which otherwise tries to compress the incompressible fuel). Incidentally, fuel is 100 percent methanol at all times. A Hilborn fuel pump is driven off the end of the dry sump's oil pump.

The ignition side of things is controlled by an electronic Bosch system, using a hall sensor in the VW dizzy and a Camira ignition module.

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We're told this scorching little vee-dub motor makes a good smack of torque from 1000 rpm to about 8000 rpm. "It's unreal, power is not a problem." Peter tries to limit it to 7500 revs - but that doesn't always suit all tracks. Sometimes it's best to wind the engine just that little bit harder.

The driveline, too, is an interesting one.

Passing on torque is a 5?-inch Quartermaster triple plate sintered clutch, a custom machined flywheel (which is only slightly larger diameter than the clutch) and a 6-inch pressure plate. The Mazda 121 automatic ring gear for the starter motor bolts to the back of the pressure plate.

The transaxle itself is a FT200 dog ring gearbox - and Peter tells us you can do a ratio change in about 20 minutes. The FT200 starts life as a 5-speeder, but - due to the weakness of first gear and superfluousness of having 5-speeds with so much torque - Peter has converted his back to a 4-speed. Clever, huh?

The built-in FT200 differential remains standard and offers good lock-up under drive load. Sprouting from it are Dave Moore Engineering axles that use Kombi CVs (which are reputedly very strong).

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Two piston AP calipers are found front and rear, together with cross-drilled discs. Note that the rear brakes are in-board, similar to the location that you'll see on some old Alfa Romeos. Peter's never had to replace any of the discs because they generally don't get that hot over the short track duration. Rims are 13 x 10 (front) and 13 x 14 (rear) circuit track type with a magnesium centre. Peter employs Avon 9.2-inch wide 20-inch high fronts and 13-inch wide 24-inch high rears. Slicks were fitted for our shoot, but there's also a set of wet tyres that are sometimes called into action.

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Peter also developed the carbon fibre aero package - the wings, side pods, engine cover and bodywork. The original nosecone was an entirely different shape when he bought the car - in fact, he's now tried three completely different ones. It's all about downforce, y'see.

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The side pods were made up from scratch - there were none fitted when the car was bought. It's all carbon fibre - except for the front under-tray, which is fibreglass. This will soon be done in carbon fibre as well - Peter tells us he lays it up using a very similar technique to fibreglass. The engine cover came off another racecar and Peter shaped it to suit.

The wing sections (based on a Formula 30000 Reynard) have been laser cut in polystyrene and wrapped in carbon fibre, so they're solid but very light. Note that the rear wing is also set a long way back from the back of the vehicle - Peter says this gives more downforce without having to use a high-drag wing section.

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Inside the cramped cockpit you'll find Racelogic traction control and data logging controls. The data logging is used (collecting information on rpm, individual wheel speed and traction control operation), but the traction control system is rarely used. Peter tells us the car is slower with the system on - you really need a bit of wheelspin at the start of the track to try to get the tyres up to temperature. Another problem with the system is it makes it harder to balance on the throttle - you can't kick the tail out with a bootful of throttle.

Also in the cockpit there's a carbon fibre seat (moulded to the shape of Peter's back), TRW harness, extinguisher, a Momo suede wheel and custom fabricated shift linkages. Gauges are for boost, oil pressure, engine rpm and EGT (which is used as a tuning guide).

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With a "wouldn't want to work it out" amount of money and an equal amount of time invested, Peter enthuses that it's truly an excellent vehicle to drive. As we said, he's won the Australian championship for the last four years in a row - often against some very exotic, imported machines. It turns in very well, carries good corner speed and gets its power down exceptionally well.

And it's not all handling either - Peter's data logged 0 to 100 km/h sprints in a mere 2.6 seconds - and that was when the car was slightly heavier!

If you've never given much thought to hillclimb racers before, you sure will now!

Contact:

Peter Gumley Smash Repairs
+61 4272 1706

RD Images
0414 633 086

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