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Senator Strength

A wicked HSV Senator stroked to 7.2-litres and breathing through an eight-throttle intake manifold!

Words by Michael Knowling, Pix by Julian Edgar

Click on pics to view larger images

At a glance...

  • 2003 HSV Senator Signature
  • All-out C5R stroker engine
  • Eight-throttle Harrop intake manifold
  • 501hp (374kW) at the wheels
  • Alcon brakes
  • Sensationally quick - and comfortable!
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It’s always intrigued us how HSV use the name Senator to represent one of its top-line performance models. We’re supposed to think of an all-powerful figure that demands quivering worship and respect from everyone around. But, if you’re like us, you’ll think of a rotund aging gentleman with an air of arrogance and a bad hair piece.

Rest assured, this particular HSV Senator – with 501hp (374kW) at the wheels – represents the former!

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Owned by Geoff Taunton, this 2003 VYII Senator Signature was purchased with the intent of creating a luxury car with the performance of the ‘teaser’ 427ci Monaro that never went into production. Yep, Geoff is a man with big plans – and the finances to back them up. So, not long after purchase, the Senator was dropped off at PowerTorque in Brisbane for what’s best described as a total transformation.

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The platform for this spare-nothing engine build is a 427ci (7-litre) C5R block which is designed for motorsport and boasts six-bolt main bearing caps. And, no, it’s not a cheap item! Add to this an aftermarket stroker crankshaft and you’re talking a total 442ci (7.2 litres) displacement. Geoff has also opted for Lunati rods and JE forged pistons which prove a compression ratio around 10.5:1 – low enough to enable the engine to run on pump fuel.

On top of the C5R block you’ll find LS6-spec cylinder heads which have been extensively ported and polished. Upgrade valves, valve springs, retainers and a double row timing chain are also installed. A plenty serious Comp camshaft teams with Yella Terra 1.7:1 rockers to provide wild valve timing and lift. You wouldn’t call the valvetrain conservative...

The entire engine assembly has been blueprinted and crack-tested. An ARP stud kit, high volume oil pump and custom sump also help keep the big banger pumping without hassles.

And check out the engine’s crowning glory – a magnificent eight-throttle intake manifold.

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Geoff bypassed the cheaper aftermarket intake manifolds to be one of the first in Australia to use the magnificent Harrop Hurricane manifold. This particular Hurricane set-up comprises eight 55mm diameter throttles (with individual adjustment to aid tuning), individual ram-tubes and Harrop’s optional ‘Installation Kit’ with two plenums, twin pod air filters and an intake tray that shields under-bonnet heat. Geoff has also added a snorkelled VZ Monaro bonnet to provide extra airflow to the filters.

Interestingly, Geoff had the chance to drive the car with and without the Harrop manifold and says it made a tremendous improvement in terms of throttle response and refinement. The monster camshaft currently being used gives a pretty lumpy idle – but the same cam used with the standard manifold was way too bad-mannered for street use.

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The new eight-throttle induction system employs MAP load sensing and the management system is tuned via VCM Suite. Injectors are massively upsized over standard and, interestingly, the standard fuel pump is up to the job. The ignition system also remains standard.

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On the exhaust side, the Senator breathes through 1 7/8-inch 4>1 DiFillipo headers leading into a twin 3-inch mandrel system with a X-pipe. DiFillipo cat converters and a pair of large body mufflers are also squeezed under the floorpan. Geoff is rapt in the exhaust system – it sounds great without being unnecessarily loud.

On PowerTorque’s Dyno Dynamics chassis dyno, Geoff’s Senator has punched out enough power to shame the majority of supercharged LS1s. This baby has run a no-BS 501 horsepower (374kW) at the wheels on pump fuel and the full exhaust system in place.

We think this Senator just moved up to world leader status!

So what sort of driveline is necessary to cope with an atmo engine as raunchy as this?

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Well, Geoff spent seven grand on tricking the standard 4-speed auto transmission and installing a 3000 rpm stall converter (the engine starts to come on song at 3000 rpm and continues to flex muscle to 7000 rpm). At the rear is the standard differential and axle set-up with minor mods to improve strength and traction.

Geoff hasn’t had the chance to run an official quarter mile pass but an ‘unofficial attempt’ showed there is easy mid 10-second performance on tap. Geoff says the car has also lined up against a proven 10.3-second car and managed to nose ahead...

But all this performance comes with a civility not usually associated with a hairy-chested V8.

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Geoff has taken pains to ensure the standard Senator leather trim goes untouched, noise levels are sane and the ride is comfortable. At present, the car rides on an off-the-shelf coil and damper combo (which drops the ride height about 2 ½-inches), but Geoff says he plans to switch to Bilsteins.

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Braking confidence is enhanced by the installation of Alcon six-pot front callipers and 383mm discs. The rear brakes remain standard HSV.

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Visually, the HSV Senator body kit is sharply styled and eye-catching – no need to change anything, except for the fitment of a genuine Holden Monaro bonnet. The rolling stock has also been upgraded to hard-to-miss Lenso 20s. Sweet.

At the time of writing, Geoff is nearing completion of this project. Aside from changing the suspension, he has plans to install genuine C5R heads (costing AUD$16,000!) and take a run at becoming the first atmo LS1-powered GM into the 9s...

We can’t think of another Senator with such incredible ambition.


PowerTorque +61 7 3881 2379

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