Holden LY7 Alloytec V6 engine (2004-09)

Introduction

Manufactured in Port Melbourne, Australia, the Holden LY7 ‘Alloytec’ V6 engine was available from 2004 to 2009. Developed by GM Powertrain, the LY7 was part of General Motors’ High Feature V6 (HFV6) engine family; within General Motors’ ‘Regular Production Option’ (RPO) system, ‘LY7’ was the code for the high output HFV6 engine.

The lower-output LE0 and LY7 engines were closely related. The main differences between these engines were that the LE0 engine did not have variable exhaust camshaft phasing and, for the VZ/WL models, a variable intake manifold.

Whereas the LE0 engine was used in the entry-level VZ and VE Commodore-based models, the LY7 was reserved for the sports or premium models such as the Commodore SV6, Calais, Statesman and Caprice. The LY7 engine was also used in the VZ Adventra due to the additional mass of its all-wheel drive system.

LY7 block and internals

Like the LE0, the LY7 engine had a deep-skirt alloy cylinder block that was cast in 319 aluminium and had six-bolt main bearing caps made from copper-infiltrated sintered steel. Within the block, cast-in inter-bay breather vents reduced windage losses at high engine speeds, while the cast-iron cylinder liners were produced using a precision sand-casting process. The cylinders had a 60-degree V’ angle, 103.0 mm bore centres, 94.0 mm bores and 85.6 mm strokes for a capacity of 3564 cc.

Similarly, the LY7 engine had a micro-alloy 1038V forged steel crankshaft (more commonly found on high performance or diesel engines), sinter-forged steel connecting rods and aluminium pistons which had polymer-coated skirts and full-floating wristpins (24 mm diameter). Furthermore, pressure-actuated piston oil-jets cooled the underside of the pistons.

LY7 cylinder head and valvetrain

The LY7 cylinder heads were produced from semi-permanent mould 319 aluminium castings and featured convergent exhaust ports for maximum flow. The upper intake manifold was made from 319 sand-cast aluminium, while the lower manifold was made of 356-T6 aluminium.

The LY7 engine had double overhead camshafts (per cylinder bank) that were produced from cast nodular iron. Initially, the camshafts were driven by 9.5 mm pitch roller chains. In January 2006, however, the roller chains were replaced by inverted tooth chains which had a 7.7 mm pitch. For the accompanying changes, please see ‘January 2006 changes’, below.

The camshafts actuated the four valves per cylinder via roller follower valve lifters which had hydraulic lash adjusters. For the LY7 engine, the inlet and exhaust camshafts had electronically-controlled, hydraulically-actuated camshaft phasing which was continuously adjustable and allowed camshaft timing through 50 degrees of crankshaft rotation.

Unlike the LE0 engine, the variable exhaust valve timing of the LY7 enabled:

• Delayed exhaust valve closing: enabled more post-combustion gases to be expelled from the combustion chamber for a bigger air/fuel charge on the intake stroke; and,
• Early exhaust valve closing: retained more post-combustion gases in the cylinder for more complete combustion and improved fuel efficiency.

The LY7 engine had a high-silicon moly (SiMo) nodular cast iron exhaust manifold, dual close-coupled catalytic converters and a dual-pipe exhaust system.

Variable intake manifold (VIM)

From launch, the LY7 featured a variable intake manifold (VIM) which used an electrically-operated valve within the manifold to affect air charging. For engine speeds below 4000rpm, the valve was closed to reduce intake volume and air was supplied via two separate plenums. Beyond 4000rpm, the valve was open and all cylinders were fed from a common plenum, increasing ram cylinder charging efficiency for greater power. It is understood that the VIM was revised for the VE range.

Injection and ignition

The LY7 engine had sequential port fuel injection and a returnless fuel system. Furthermore, the LY7 engine had

• coil-on-plug ignition;
• extended-life (120,000 kms) spark plugs with dual-platinum electrodes;
• electronic throttle control; and,
• a compression ratio of 10.2:1.

For the VZ range, the LY7 engine had a 32-bit Bosch Motronic ME9 engine control unit (ECU). For the VE range, however, this was replaced by the Bosch E77 system which included digital crank and camshaft position sensors.

Power outputs

Initially marketed as the ‘Alloytec 190’ for the Holden VZ range, the LY7 engine produced 190kW at 6500rpm and 340Nm at 3200rpm. Significantly, however, 90 per cent of peak torque available from 1570 rpm to 5870 rpm; maximum engine speed for the LY7 was 6700rpm.

For 2006, peak torque for the LY7 engine decreased from 340Nm to 335Nm as the engine was detuned for Euro III emissions compliance. For the VE range, peak power increased to 195kW and torque returned to 340Nm.

January 2006 changes

In January 2006, the following changes were introduced for the LE0, LY7 and LW2 engines:

• The top piston ring underwent nitride treatment for greater durability;
• The crankshaft balancer was changed from a three to a six spoke design;
• For Euro III emissions compliance, the engine was detuned, fitted with new fuel injectors and a new catalytic converter; and,
• The camshaft drive chains were changed from a 9.5 mm roller chain to a 7.7 mm inverted tooth design (known as a ‘silent’ or ‘Morse’ chain). In turn, this led to changes in:
  • The camshaft, crankshaft and intermediate drive sprocket tooth shapes;
  • Camshaft actuators, tensioners, chain idler sprockets and chain guides;
  • The front engine covers;
  • The camshaft covers; and,
  • The camshafts sensors were switched from analogue to digital operation – this resulted in a change to the engine harness connector for these components.

LY7 V6 engine: stretched timing chains

In January 2006, 7.7 mm inverted tooth timing chains were introduced for the LE0, LY7 and LW2 engines, replacing 9.5 mm pitch roller chains. For some – but not all – of these timing chains, the chain links were not manufactured in accordance with design specifications and the chains could become elongated (also known as ‘stretched timing chains’). According to GM Bulletin H08-0601-01, chain elongation was expected to occur in early engine life (i.e. 10,000 kms to 20,000 kms). There have, however, been reports of timing chain elongation occurring at significantly higher kilometres.

Elongation of the timing chains would cause,

• the Malfunction Indicator Lamp (MIL or ‘Check Engine’ light) to illuminate; and
• the ECU to log fault codes P0008, P0009, P0016, P0017, P0018 and P0019 which indicated that camshafts on either bank of the engine were misaligned with the crankshaft.

The engines with timing chains susceptible to elongation were produced from January 2006 to engine build date 18 May 2007 (18/5/2007); this production range corresponded to engine numbers between H053340001 and H071380576.

The typical chain elongation observed was a minimum of 3 mm on a doubled-up chain. Where the timing chains had become elongated, they had to be replaced. The idlers, guiders and tensioners, however, did not require replacement, though the guides should be inspected for any abnormal wear.