Holden Commodore (VN-VZ), Frequently Asked Questions

What engines were available across the VN-VZ range?

The VN-VZ used three main engine families:

• 3.8L V6 (Buick/Ecotec): VN-VY. Pushrod, overhead-valve. 125-172 kW depending on model year and specification. Supercharged versions (L67) were available through HSV and some late Commodore models.
• 3.6L V6 (Alloytec): VZ only. DOHC, 24-valve, all-aluminium. 175 kW. A modern engine with more power and efficiency than the Ecotec.
• 5.0L V8 (Holden 304): VN-VT (Series I). Pushrod, OHV, iron block. 165-185 kW. The last of the traditional Holden V8s.
• 5.7L V8 (LS1): VT II-VY. All-aluminium, OHV. 225 kW. The same engine as the Chevrolet Corvette C5.
• 6.0L V8 (LS2): VZ. All-aluminium, OHV. 260 kW. Shared with the Corvette C6 and Pontiac GTO.

HSV models used enhanced versions of these engines, with additional power from calibration, exhaust, intake, and (in later models) supercharging.

What is the difference between the VT and VT II?

The VT Series I (1997-1999) used the Ecotec 3.8L V6 and the Holden 304 5.0L V8. The VT Series II (1999-2000) replaced the 304 with the LS1 5.7L V8 on V8 models. The V6 remained unchanged. The VT II also introduced the T56 6-speed manual gearbox option on SS and HSV models.

This is a critical distinction for buyers. The VT II SS with the LS1 is a fundamentally different car from the VT I SS with the 304. The LS1 is lighter, more powerful, more refined, and has vastly more aftermarket support. If you’re buying a V8 VT, make sure it’s a Series II.

What is the LS1 and why does everyone want one?

The LS1 (RPO code LS1, Chevrolet’s internal designation) is a 5.7-litre, all-aluminium, pushrod V8 designed by GM Powertrain. It was introduced in the 1997 Chevrolet Corvette C5 and fitted to the VT II Commodore SS from 1999.

Everyone wants one because it’s one of the best V8 engines ever made. It combines the simplicity and torque of a pushrod V8 with modern materials and manufacturing precision. The aluminium construction makes it light (under 200 kg), the 225 kW factory output is strong, and the aftermarket is the largest of any V8 engine on earth. A cam, headers, and tune will reliably add 30-50 kW. With forced induction, 400+ kW is achievable on a stock bottom end.

The LS platform (LS1, LS2, LS3, LS7, LSA) has become the default performance V8 worldwide. Parts from American suppliers (Summit Racing, Jegs, Texas Speed) fit directly. This global ecosystem means the VT-VZ Commodore SS is one of the most modifiable performance cars on the planet.

What is DOD/AFM and should I worry about it?

DOD (Displacement on Demand) is GM’s cylinder deactivation system, fitted to some VZ LS2 V8 models. Under light load and steady throttle, the system deactivates four of the eight cylinders to save fuel. The system uses special lifters with internal locking mechanisms.

You should be aware of it because the DOD lifters are a known failure point. The locking mechanism can fail, causing the lifter to collapse, which leads to misfiring, rough running, and potentially camshaft and pushrod damage. High-mileage VZ V8s with DOD are particularly susceptible.

Many owners disable DOD via an ECU tune and replace the DOD lifters with standard non-DOD lifters. This eliminates the failure mode and is considered a worthwhile upgrade for any VZ V8 with DOD. The fuel economy penalty of running on all eight cylinders full-time is minimal.

Not all VZ V8s have DOD, it depends on the specification. Check your car’s RPO codes (on the sticker in the glovebox or boot) to determine if DOD is fitted.

How do I tell which gearbox my car has?

Manual models:

• VN-VS: Borg Warner T5 5-speed (most models) or Getrag 260 5-speed
• VT II-VZ: Tremec T56 6-speed (SS and HSV models)

The T56 has a distinctive 6-speed gate pattern, 1st is up-left, reverse is down-right with a lockout collar.

Automatic models:

• VN-VY V8 and all V6: 4L60-E 4-speed (various versions)
• VZ V8 (some): 4L65-E (strengthened 4L60-E) or 6L80-E 6-speed

The 6-speed auto in the VZ has an “M” (manual/manumatic) gate on the shift lever with + and - positions. The 4-speed has the standard P-R-N-D-3-2-1 gate.

Can I swap an LS1 into a VN-VS Commodore?

Yes, and it’s one of the most popular engine swaps in Australian performance car culture. The VT II LS1 and its associated wiring loom, ECU, and exhaust can be fitted into VN-VS Commodores. The swap requires:

• LS1 engine, wiring loom, and ECU (complete dropout from a VT/VX wreck is ideal)
• Engine mounts (aftermarket conversion mounts from companies like Hi Octane Racing or VCM Performance)
• Gearbox crossmember modification or replacement
• Exhaust headers (specific LS1-into-VN/VP/VR/VS headers from Pacemaker or similar)
• Radiator hose modification
• Driveshaft modification (length and yoke)

The T56 manual usually comes with the LS1 swap. The 4L60-E auto also bolts up. The swap is well documented, with detailed guides available on forums and YouTube. A competent home mechanic can complete the swap in a couple of weekends.

Budget $8,000-15,000 for a complete LS1 swap into a VN-VS, including the engine, conversion components, and basic tuning.

What’s the difference between the Ecotec and Alloytec V6?

They are completely different engines.

Ecotec 3.8L (VN-VY): Buick-derived, pushrod, OHV, 12-valve, iron block with aluminium heads. 3,791 cc. 125-172 kW depending on specification. Simple, tough, and well-understood. Cheap to maintain. The intake manifold gasket leak is the primary concern.

Alloytec 3.6L (VZ): GM High Feature V6, DOHC, 24-valve, all-aluminium. 3,564 cc. 175 kW. More powerful and refined than the Ecotec, but more complex. The timing chain and plastic guide failure is a significant and expensive issue. The Alloytec uses variable valve timing, coil-on-plug ignition, and a drive-by-wire throttle, all adding complexity.

For a low-maintenance car, the Ecotec (VY or earlier) is the safer choice. The Alloytec is the better engine on paper but carries higher maintenance risk and repair costs.

What fuel should VN-VZ models use?

• V6 (all variants): 91 RON unleaded. 95 RON provides marginal improvement.
• 304 V8 (VN-VT I): 91 RON unleaded. 95 RON recommended for SS models.
• LS1 5.7L (VT II-VY): 95 RON premium unleaded. 98 RON recommended for modified engines.
• LS2 6.0L (VZ): 95 RON premium unleaded. 98 RON for HSV models.
• HSV (all): 98 RON recommended.

E10 is acceptable for all models but offers no benefit and may cause issues in older fuel systems.

How much power can a stock LS1/LS2 handle?

The LS1 bottom end (block, crank, rods, pistons) is reliable to approximately 350-400 kW at the flywheel with proper supporting modifications (cam, headers, intake, tune, and adequate fuel system). The hypereutectic pistons are the weak point, they don’t tolerate detonation well.

The LS2 has a similar limit, perhaps slightly higher due to the larger displacement and revised internals.

Beyond 400 kW, most builders upgrade to forged pistons and connecting rods. With forged internals, the LS1/LS2 bottom end is good to 600+ kW.

The global LS community has pushed these engines to extraordinary power levels. 1,000+ kW builds exist, though these use extensively modified bottom ends, aftermarket blocks, and massive turbo or supercharger setups.

For a street car, a cam, headers, exhaust, and tune on a stock LS1 will reliably produce 270-290 kW at the flywheel. That’s a seriously fast street car in a Commodore chassis.

What’s the best first modification for a VT-VZ SS?

The proven recipe, in order:

1. Exhaust: Cat-back exhaust system, 2.5” or 3” depending on preference. This alone adds 5-10 kW and transforms the sound. Budget $800-1,500 fitted.
2. Headers/extractors: Pacemaker, Hurricane, or similar. 1 5/8” primaries for a street car. Adds 10-20 kW when combined with the exhaust. Budget $600-1,200 fitted.
3. Cold air intake: LS1 benefits from cooler, denser intake air. A proper cold air intake (not a pod filter in the hot engine bay) adds 3-8 kW. Budget $200-400.
4. ECU tune: A professional dyno tune optimises fuel and timing for the modifications above. This is where the real gains appear, a tune typically unlocks 15-25 kW beyond the bolt-on gains alone. Budget $400-700.
5. Camshaft: The big one. An aftermarket cam (Texas Speed, Comp Cams, VCM Performance) transforms the LS1. Budget $1,500-3,000 for the cam, springs, and installation. Expect 30-50 kW gain.

Exhaust, headers, and tune first. Cam later when you want more.

Is the VN-VP worth buying or should I go straight to a VT?

It depends on your budget and what you want.

VN-VP pros: Cheap to buy, simpler mechanicals (no CAN-bus, no BCM), the 304 V8 has a classic Holden character. Good platforms for modification and LS swaps.

VN-VP cons: Rust-prone, dated interior, less refined ride and handling, no LS1 option from the factory.

VT onwards pros: Dramatically better build quality, LS1/LS2 V8 option, superior ride and handling, more modern interior, better rust protection.

If you’re buying a daily driver, the VT onwards is the obvious choice. If you’re buying a project car or something to modify on a budget, the VN-VS offers a cheaper entry point with the expectation that you’ll spend more on improvements over time.

The VT is the dividing line in this range. Everything changes with the VT.

How do I verify an HSV is genuine?

HSV models have a unique build plate (separate from the Holden VIN plate) that identifies the HSV model, specification, and build number. The build plate is typically located in the engine bay or on the firewall.

To verify authenticity, contact HSV directly or the HSV Owners Club. They can confirm whether a build number is legitimate and matches the claimed specification. HSV also maintained production records that can be cross-referenced.

Key things to check:

• HSV build plate matches the car’s VIN
• Engine specification matches the claimed model (e.g., GTS should have enhanced engine calibration, not a standard SS engine)
• Interior specification matches (GTS has unique seats, trim, and gauges)
• VIN falls within the known production range for that HSV model
• Original sales documentation and service history from HSV dealers

Given the values involved (VT-VZ GTS models are $50,000-90,000+), professional authentication is money well spent.

Are parts still readily available?

Extremely. The VN-VZ Commodore was the best-selling car in Australia for most of its production life. There are millions of them on the road and in wreckers.

For the LS1 and LS2 specifically, parts availability is essentially unlimited. These engines were used globally in the Corvette, Camaro, GTO, Pontiac, and countless other GM vehicles. American aftermarket companies like Texas Speed, Summit Racing, and Jegs ship to Australia, and local suppliers like VCM Performance, Hi Octane Racing, and LSX Unleashed carry extensive LS inventories.

V6 parts (Ecotec and Alloytec) are abundant from wreckers. The Ecotec shares components with the Buick Riviera, Pontiac Grand Prix, and other GM vehicles.

Body and trim parts for VT-VZ models are still easy to find. VN-VS parts are becoming scarcer for specific trim items and interior components, but mechanical parts remain plentiful.

The Commodore community is one of the most active in Australia. Forums, Facebook groups, and dedicated online stores mean you’ll never struggle to find what you need.