How to Port & Polish an Intake Manifold

Power can be gained from widening (porting) the intake ports and polishing them afterwards. In order to do this, you'll need a number of tools which can grind away the particular metal the intake manifold you are porting.

Many intake manifolds are cast metal and contain remnants from the casting process. These are sometimes found in the ports themselves, reducing flow efficiency.

The Porting Process

Porting involves grinding away excess material in the inside of an intake manifold to improve the flow. Small passage ways tend to restrict how much air can easily pass through at a given amount of time, so widening them can reduce the level of effort the engine has to put out, improving its performance.

Improving Flow Rate

Just making the intake ports a larger diameter doesn't create the best possible result. Sharp angles in the channels can restrict flow efficiency, so reducing the sharpness of these angles can improve the flow rate through the intake manifold.

Outside, Inside, Outside

Similar to a preferred race driving line, a port angle's sharpness can be reduced by grinding away material in the right places, starting on the outside of the corner, just as the bend begins, then on the middle of the inside of the corner, and then on the last bit of the outside of the corner. The channel leading up to the bend and leading away should be ground to match the new shape for maximum improvement.

The Polishing Process

Polishing is done after porting (or just in general) to remove rough surfaces from the inside of the intake manifold.

Air/Fuel Mixing Zones

The area where fuel is injected should be considered when polishing. Smooth surfaces can sometimes attract the fuel the passes by it, causing it to leave the air heading in to the engine, and stick to the inside of the intake manifold, and this makes the burn level less predictable, which costs both fuel economy and power.