First published in the December 1990 issue of Street Machine. Photos Peter Bateman

For hauling arse or kicking it, you can’t beat a trip to Canberra. From the Senate to the Summernats, power is the name of the game and when the parliament of grunt meets every New Year to elect a new leader, only the toughest survive. Canberra local Graham Oldfield is into power – whether it’s rearranging the national capital’s landscape during the day as an earthmoving contractor or putting a bit of topspin on the globe with Fat Rat, arguably Australia’s toughest early-model Holden.

Graham had been toying with the idea of building something to take a crack at the Summernats title for some time, but couldn’t quite settle on a plan. Then, when flipping through the classifieds for some inspiration, he came across a ‘home wanted’ ad for the ex Bill Parks rat-powered humpy and knew immediately which way to go. And when he saw the quality of engineering on the car, he knew exactly where to start. Yep, he slapped down the readies and took it home. Nine months and $60,000 later, this neat 48/215 sure has what it takes for a shot at the top.

Graham and Bill are keen to acknowledge each other’s input into the car too: something that’s rare in Canberra’s other power game. Bill started work on the car around nine years ago, initially as a drag car to promote his business, Trans-Pacific Body Repairs at Kirrawee, NSW. Early on in the three years it took to build, Bill decided to go one step further and make it street legal – a wise move as it turned out, as Sydney’s Castlereagh drag strip was kaput before the car was finished and it never saw the track.

As the car stands today, Bill’s contribution is in the engineering and body mods necessary to handle the grunt of the Chevy 454 – the widened rear guards and bonnet louvres are Trans Pacific’s handiwork, as is the modified HQ ute chassis the lot sits on (Graham has since strengthened the chassis for future mega grunt).

So much for history. What you see now is one mean mutha, thanks to Graham Silk from Queanbeyan Engine Services. That louvred lid hides the same 454 Bill shoehorned way back then, but all he’d recognise now is the engine number. Graham’s idea of grunt runs to a Low-Blow B&M blower and drive, MaddeNitrous happy gas injection and a Holley 850 mechanical double pumper.

To take advantage of this hardware, the block was reamed 30 thou and fitted with TRW 8:1 flat-top blower slugs, LS7 conrods and a steel crank – held under control by four-bolt mains. Crane takes care of the valve operation from the hydraulic camshaft to the pushrods. Up top, Yella Terra roller rockers operate LS7 valves and Manley double valve springs. Heads are brand-spanking LS7 big ports and the intake manifold is B&M, sitting on top of a custom-made (by MaddeNitrous) spacer to house the nitrous injectors.

Fuel feed is by Holley high-volume mechanical pump and regulator while the used stuff exhausts via modified Corvette headers feeding a dual 21/2-inch stainless system by Tuggeranong Exhaust Centre. Keeping the Rat friction-free and cool is the responsibility of a Mellings hi-vol oil pump and a five-core radiator from a Ford Thames Trader truck.

And what does all this heavy-duty gear add up to? Well, Graham hasn’t put Fat Rat on the dyno yet – the fact that not all dynos are heavy-duty enough for this sort of muscle is undoubtedly a factor – but at the ACT titles he was reckoning on much better than 500 neddies without nitrous. Later consultation with expert engine builders upped the theoretical figure to more like 800 horsepower. And with the nitrous clicked in? Well, Graham says 1000-plus horsepower would be a conservative estimate.

The theme of Yank gear and Aussie ingenuity carries through to the transmission. A TCI 3300 stall converter drives a TH400 trans tricked to full manual by Woden Valley Transmission Centre and using Allison truck clutch packs. Shifting is by B&M and the tailshaft is a modified HJ Holden spinning a 3.25:1 ratio version of God’s own diff, the Ford 228.6mm (work it out, we’re sick of writing it the other way) limited slip. The grand final drive is housed in a cut-and-shut and disc-braked XW GT Falcon (phew) rear axle assembly and tortures the tarmac via a pair of ’61 Tank Fairlane axles. Brakes are four-wheel disc courtesy of Ford XD and PBR.

The oh-so-smooth Monza Red top coat is also courtesy of Ford. The 12 coats of Spartan acrylic were rubbed back after every three coats, with two 50/50 clear and colour coats to finish it off. Inside, the original dash carries VDO amp, oil, fuel and temp gauges and Mallory reports on the engine revs. The speedo is the original and does its best to cope when the needle goes off the end at 110mph. Front seats are Recaro, retrimmed by Bill in Ford Palamino leather-look vinyl and the hoodlining is perforated white vinyl. A modified Chevette adjustable steering column carries a Chevette wheel. Detail touches include the handmade knobs, spun up by ‘Deano Machino’ from Canberra Machining Company.

The final touch to this humungous Humpy are the full-chrome Prowire steel wheels – 14×6 up front and 14×9 at the rear – made by the Wheel Factory in Queanbeyan and shod with Yokohama 225/145 and 245/145 rubber.

While he built the car mainly for pleasure, Graham has set it up with its own truck to go show touring and has already grabbed a swag of trophies including Best of Show at the ACT titles in Canberra. There’s a lot to be said for classic Aussie tin and Yank grunt. This is one mean 48/215.

GRAHAM OLDFIELD
48/215 HOLDEN