WHEN you spend a year working on improving a car you’ve built, you will get to know it intimately and have it singing. But Martin Mohan has spent more than seven years refining and developing his turbo 427ci VX Berlina into a 1300rwhp sleeper that has – so far – gone 8.8@159mph on the quarter.
This article was originally published in Street Machine LSX Tuner #5
The truly impressive feat is that Martin drives the 1700kg wagon, which retains the original M80 independent rear end, to and from the track. Making such a heavily compromised car work that well is also testament to the hard work the team from Russo Performance have put in over the years, taking it from a turbo iron truck motor to the latest set-up featuring some of the best hardware the LS aftermarket can provide.
The block is an aftermarket aluminium 427ci unit from Racing Head Services (RHS), which is a factory-style bolt-in replacement with a few serious upgrades that make it perfect for applications making up to 2000hp. Longer cylinder bores reduce piston-rock and oil consumption, while the billet steel main caps reduce the risk of block twist.
The block also uses a factory-style priority oiling system, with a stock wet sump being fitted under Martin’s VX. RHS drills and taps its blocks to accept bolt-in oil squirters, to keep the underside of the pistons cool.
The Russo boys filled the new lightweight block with good gear to handle up to 30psi of boost, installing the Manley crankshaft, Oliver Pro billet conrods and CP pistons, plus a Comp Cams solid bumpstick ground to custom Russo Performance specs.
The RHS block also accepts six-bolt head designs, like the pair of Higgins HRD units fitted to Martin’s car. Formerly known as the CID head, these deep-breathing units feature altered geometry to increase performance, which is important when you have a Garrett GT55 turbo ramming charge-air into the combustion chamber at warp speed!
With so much work going into the basics of the current combo, the valvetrain was never going to be made up of eBay parts, so Morel Race Series lifters were installed into the block, acting on 3/8-inch pushrods and heavy-duty T&D shaft-mount rockers. Mounting the roller rockers with a shaft system rather than the stock-style studs aids in keeping the valvetrain geometry correct, especially in high-rpm combos like Martin’s.
Running on E85, the wagon has a voracious thirst, lifting the corn syrup out of a rear-mounted fuel cell living in the spare tyre well into a pair of staged Holley 1800 pumps, then down the Teflon braided lines to 16 Bosch ID2000 injectors and Turbosmart fuel pressure regulators that have been mounted off the side of the Shaun’s Custom Alloy intake manifold. Sitting on the front of the sexy plenum is a factory 90mm LS3 fly-by-wire electronic throttlebody, which Russo has fitted up in place of the VX’s stock cable assembly as a way of incorporating traction control through the Haltech Elite 2500 ECU down the track.
The Haltech ECU is a recent upgrade from a flash-tuned Holden PCM, as the aftermarket computer can offer far more controls, including pyrometers in each exhaust header, capacitor discharge ignition (CDI), torque-metering traction control and more. Russo has enabled most of these technologies during the latest round of upgrades in the hopes of improving how the wagon gets out of the hole, as traction is proving to be a serious issue.
Causing some of these traction issues is the Garrett GT55 full-frame turbo sitting behind the passenger headlight. It’s mounted on a Russo Performance turbo manifold and blows up to 30psi into a Plazmaman front-mounted air-to-air intercooler. Waste gases are expelled via a four-inch exhaust system that has been plumbed with a Tial wastegate. Extra plumbing comes from the custom alcohol injection system Russo pieced together to safeguard against detonation, activated once the Turbosmart e-Boost boost controller hits 18psi.
Sitting behind the angry seven-litre LS is a Turbo 400 three-speed auto built by Craig’s Automatics and paired to a Dominator torque converter. It is a fairly traditional street machine set-up, but things get more adventurous at the rear end.
Along with mini-tubbed wheelarches to give drag radials more real estate, the Russo boys have now changed the stock IRS cradle to take adjustable Strange coil-over struts, rather than the OEM separate spring/shock set-up, mounted where the stock shocks bolt into. In addition to this, the factory M80 diff has a full-spool centre and 31-spline stub axles mating to 1400hp CV shafts from Diff Technics, who also supplied the carbon driveshaft.
Recently the wagon was strapped onto a hub dyno and made 1315rwhp at 30psi on E85, which should translate into new PBs at the strip once the boys find some traction. Before the ECU and suspension upgrades, Martin has stopped the clocks at 8.8 seconds and 159mph with a fairly lazy 1.51 60ft time, though his trap speed has been as high as 162mph and the 60ft as low as 1.43.
“Since we’ve upgraded engine management we’ve struggled with traction. We are trying to get into the low eights, but it’s a tough gig when you drive it to the track,” Justin Russo laughs.
One thing is for sure: Once they have it hooked up this wagon will be incredibly hard to beat, thanks to the wealth of experience gained during its evolution. Hopefully we can see it on Street Machine Drag Challenge one day!
Martin Mohan - Holden VX Berlina Wagon
Type: RHS aluminium
Rods: Oliver billet
Intake: Shaun’s Custom Alloy
Turbo: Garrett GT55
ECU: Haltech Elite 2500
Intercooler: Plazmaman air-to-air
Gearbox: TH400 auto
Tailshaft: Diff Technics carbonfibre
Diff: Factory IRS M80, full spool, Diff Technics CVs & 31-spline stub axles
Springs: King (f), Strange coil-over struts (r)
Rims: HSV Pentagon; 20x8 (f), 20x9 (r)
Rubber: 235/35 (f), 275/30 (r)
Russo Performance; Craig’s Automatics; Haltech