Variable Valve Timing (VVT) is a system that automatically adjusts valve timing.

GM used VVT on the following engines within the LS family.

LS VVT Applications

DisplacementRPO Code
4.8LL20
5.3LLC9LH9LMFLMG
6.0LL76L96LC8LFALY6LZ1
6.2LL92L94L99L9H

(Summit Racing’s Paul Spurlock and Brian Nutter contributed to this article.)

How Does VVT Work?

The computer senses engine load. It also monitors valve timing through the camshaft position sensor. It then uses that VVT data to determine the best valve timing for the current conditions.

The computer sends a signal to a solenoid on the timing cover. The solenoid controls oil flow through a special control valve in the camshaft bolt. The valve sends oil into the phaser control chambers.

The actuator rotates one way or the other, depending on the oil flow. That rotation is used to advance or retard the camshaft as needed.

How Does VVT Affect Performance?

VVT gives you the best of both worlds. It can advance valve timing for a smooth idle and low-end torque. It can also retard the valve timing for more top-end power. And, it’s all done automatically.

VVT becomes an issue when swapping a cam:

  • Piston-to-valve clearance can be a problem.
  • Your choices for valve lift and duration are limited.
  • The high spring pressure required for performance cams can overpower the actuator.

If you want to upgrade your camshaft and keep the VVT system, you will need a Camshaft Phaser Limiter.

If you want high performance from a bigger cam, you will need to delete the VVT system. (More on that in a second.)

How You Can Tell Whether Your LS has VVT

Engines with VVT will have a camshaft phaser actuator on the timing cover. They also have a five-pin connector for the VVT and camshaft sensor.

Engines without VVT will not have the actuator. They only have a three-pin connector for the camshaft sensor.

LS Gen 4 Timing Covers VVT
These are two LS engine timing covers. The one on the left has the camshaft phasing actuator, indicating that it is from an engine with VVT. The one one the right has no actuator, so it is from an engine without VVT. (Image/Summit Racing)

GM used two different actuator designs.

In 2007-08, the actuator has 62-degree rotation. GM part number 12585994.

In 2008-15, the actuator has 52-degree rotation. GM part number 12606358.

How Can I Delete the VVT on my LS Engine?

Eliminating the VVT system is required when swapping to a non-VVT camshaft. These cams offer higher valve lift and longer duration for more performance.

A VVT delete kit removes the VVT components and replaces them with standard parts. At a minimum, they include:

  • A Gen. 4, non-VVT timing cover
  • A new, 4X, non-VVT upper timing gear
  • A new harmonic balancer bolt
  • New camshaft bolts

Some kits will also include additional parts, such as:

  • A new lower timing gear
  • A new timing chain
  • A new timing chain guide

The type of VVT Delete Kit you need depends on the camshaft you are using.

1-Bolt Camshafts

3-Bolt Camshafts

Eliminating the VVT system is required when swapping to a non-VVT camshaft. These cams offer higher valve lift and longer duration for more performance.

After installing one of these kits:

  • You will be locked-in to the valve timing.
    • The computer will no longer automatically adjust the valve timing.
  • You will also need to tune the computer.
    • This will optimize the fuel and ignition curves for the new camshaft, and turn off the VVT system in the computer.

…

NOTE: You can find engine specs and detailed engine upgrade advice for every LS and LS-based Vortec truck engine in one place: The Definitive Guide to LS Engine Specs and LS Engine Upgrades.

Keywords
engine tech, GM LS engines, LS engines, VVT
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Author: OnAllCylinders Staff