Product no.: MI608
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Exclusive to Mace Engineering is our design-registered plenum spacer to suit Holden Ecotec 3.8L V6 engines.


What is a plenum spacer and what does it do?

A plenum spacer thermally separates the plenum cover and intake manifold. Its main purpose is to improve air distribution between cylinders by slowing down the air speed inside the plenum chamber. As a result there is less of a pressure drop inside the plenum chamber between cylinders, and less air momentum, resulting in better air distribution and power. The change in airflow characteristics is shown in the diagram below.



Not only will our spacer help you make more power, it will also help prevent any costly rebuilds through dangerous lean outs that occur due to poor air distribution with standard manifolds in high horsepower/boost applications.

In addition to improving air distribution between cylinders, the increase in plenum volume also has a positive effect on bottom end torque.

The fact these spacers are manufactured from the same thermal resistant composite material as our manifold insulators means further horsepower gains are possible due to the reduction in heat soak. 


Key Benefits:

  • Design registered.
  • Reduces charge air temperature resulting in better power consistency and detonation prevention.
  • Power increase with no undesirable side effects.
  • Improved air distribution between each cylinder.
  • Improved fuel economy.
  • Easy to install.
  • Can be used as a replacement gasket.
  • Reusable.
  • Proven gains at an affordable price.



  • 1 X Plenum spacer
  • 1 X Bolt pack
  • 1 X Silicone gasket maker

Vehicle Fitment Guide



Parts Guide



Please select the part number you require from the drop down menu by utilising our vehicle fitment guide and parts guide.



  • The 25mm plenum spacer is recommended for turbo or supercharged applications only.
  • Installation is very straight forward, requiring only the removal of your plenum cover to install the plenum spacer.

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Browse these categories as well: Plenum Spacers, V6, Ecotec 3.8L V6, Mace Performance Products