How to Port & Polish an Intake Manifold

Written by william zane
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Porting and polishing an engine's intake manifold is an essential step in optimising its performance, particularly if it is a modified engine. Porting is the process in which material on the intake manifold is removed to open up and enlarge the ports while polishing smooths out the surface. Both methods optimise air flow into the motor and thereby increase horsepower. The job is labour intensive and expensive if you pay someone to do it, but it can be done by yourself with the proper tools and knowledge.

Skill level:

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Things you need

  • Porting and polishing kit
  • Socket and ratchet
  • WD-40
  • Manifold gasket
  • Machinist's blue dye

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  1. 1

    Remove the intake manifold from the motor. On modern cars this will usually involve removing multiple components to allow the manifold to be removed but will vary from car to car.

  2. 2

    Use a manifold gasket to determine where and how much to port the manifold. Place the gasket over the surface that mates up to the engine. The material between the edge of the holes on the gasket and the edge of the holes on the manifold is what needs to be removed.

  3. 3

    Mark the area to be removed with machinists dye or fasten the gasket to the manifold as a guide.

  4. 4

    Remove the excess material and open up the ports with a high-speed, air-powered die grinder and a rough cutting stone. Move the cutting stone consistently around the edge of the port, taking care to not remove material that is covered by the gasket itself. Clean the manifold with DW-40 periodically to prevent the polishing tools from getting gummed up.

  5. 5

    Smooth out the edges of the port once the material is removed with increasingly higher grit polishing pads and cones. Smooth the edges of the opening into the manifold to give the air a smooth, progressive passage.

  6. 6

    Inspect the insides of the intake tracts for casting marks and rough areas.

  7. 7

    Remove the casting marks and smooth out the bends where the manifold changes direction with a rough cutting stone on the die grinder. This will promote air flow through the manifold as it moves to the engine.

  8. 8

    Polish the inside of the intake manifold with increasingly finer polishing cones. Finish the polishing with 120-grit sandpaper. NOTE: Do not polish the intake tracts until they are completely smooth, since this will inhibit fuel atomisation.

  9. 9

    Reinstall the intake manifold in the reverse of removal. Start the car and check for leaks between the manifold and the engine.

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