STAGE WRITE
FROM FARMHOUSE TO RUNNING MID-10S, THE BUILD OF JASON DAVIDSON’S TONNER TOOK EIGHT WEEKS, AND THE TOTAL COST WAS AROUND $8K
ONE of the cars at last year’s Drag Challenge that impressed me was Jason Davidson’s 3606lb, 10.63-second HQ One Tonner. The innocuous white 253/four-speed sleeper was bought off a chicken farmer for $125, and has completed five DC events.
The humble Holden was covered in chook poop and full of rats’ nests when Jason acquired it. The original running gear was turfed out and fitted with a $500, 1999 5.7-litre LS from the wreckers and a B&M transbraked, two-speed Powerglide for its first venture south. From farmhouse to running mid-10s took eight weeks, and the total cost to build was around $8K.
Jason is a fitter by trade and performed nearly all the work himself. For instance, the Ford F100 diff had all the brackets removed, narrowed and new saddles welded on in his own homemade nine-inch jig. The axles are now stock 28-spline Holden One Tonner items. The standard rear leaf springs had the short bottom helper spring removed so they’re now three-pack springs with homemade slapper bars. The front traction-bar rubbers cost $23. Originally a stock 3.9:1 ratio LSD Ford centre was used, but has now been upgraded to a 28-spline Truetrac. For rear shocks, Jason fitted the One Tonner with a $65 pair of generic no-name soft shocks from a local suspension shop. The front end has six-cylinder springs with grey Competition 90/10 shocks. Mickey Thompson tyres are fitted front and back on 15x6 and 15x10 rims, and at the super-sticky Swan Hill strip the budget-built streeter was just sneaking the front tyres off the track.
The only change to the stock early-model 5.7-litre LS bottom end is that it’s been fitted with a Holley muscle car sump. A Lunati cam, lifter and spring kit were installed along with a Pro Systems 825cfm double-pumper on a preloved Edelbrock Victor Jr manifold. Two Holley black electric fuel pumps feed 98-octane at 7psi from a stock HQ fuel tank to the carb and the second-hand, $200, single-stage 100hp OZNOS nitrous system. To light the laughing gas, an MSD 6AL LS programmable ignition with nitrous retard and rev limiter is used. Many of the parts needed were sourced online; the bucket seats came off Gumtree, while the twin-thermo-fan alloy radiator came from ebay. Jason’s One Tonner is a perfect example of what can be built on a low budget.
For some parts though, Jason had to bite the bullet and open up the wallet. The twospeed was replaced by a new $2500 TCI three-speed TH350, and the 4500rpm stall converter set Jason back $1200. The TCI unit is a full-manual, normal-pattern auto and is much better for the street than the Powerglide. There’s no transbrake; footbrake launches are fine for DC events. Gibson Driveshaft Services in Newcastle also made up a new tailshaft.
The four-into-one Castle headers run into dual 2½-inch pipes that are fitted with Hooker Aero Chamber mufflers.
A used NOS nitrous controller has been wired in, which feeds in up to 200-250hp of giggle gas down the track. Jason started racing with a 100hp shot off the line early on, but found it was too difficult to hook up, hence the nitrous controller.
There’s not much else that has gone into this 10-second Tonner other than a homemade hoop and taxi bar. It is so simple it’s almost embarrassing.
Like a few people, Jason is looking forward to racing at Drag Challenge Weekend in Queensland in May. I’m not sure what strategy Jason uses when racing the Holden in the K&N Dial Your Own class, but here are my thoughts.
For me, a nitrous or turbo car has a distinct advantage in DYO, especially with nitrous controllers and programmable boost. The nitrous cars have an advantage in consistency, as they always have cold air day or night. I don’t know how naturally aspirated DYO competitors get on racing at, say, Calder in the heat on Day One and then finishing off in the cool night air on Friday. The only way I can see to run the same times in an NA car on the Friday would be to take some timing out or short-shift to slow the car down. Or simply back off before the finish line. From what I saw last year, some racers have got whatever strategy they use down to a fine art and ran within thousandths of their dial-in.
One track I could see a DYO racer going quicker is Swan Hill, because of the traction. The startline bite was ferocious. Turbo cars have the advantage of being able to dial the launch boost back. I seem to remember one competitor in a ’67 Camaro dialling his Barra boost back to 1psi off the startline at Swan Hill.
A real problem in the DYO bracket could be going quick on Day One, then not being able to match the times at subsequent tracks. For a nitrous or turbo car, it’s easy to add more horsepower, but for an NA car that’s like game over. The only strategy for an NA streeter in DYO that I can see would be to soft-tune or short-shift on Day One.
There’s one thing I know for a fact regardless of what strategy is used: Everyone I spoke to who raced in DYO had a great time and was coming back for more.