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What is cylinder head porting and polishing?

What is cylinder head porting and polishing?

Your cylinder head, or cylinder heads if you have V engine, is an important bit of kit. It’s where the air and fuel a passed through to the valves, which in turn deliver that all important mix to the cylinder block. It does this by playing home to the valves, which again are deeply important.

And then, when the good stuff as been ignited, the cylinder head directs the spent gasses to the exhaust manifold and then out the back of the car.

The cylinder head is a vital part of your engine. If the engine block is the heart, the cylinder is the lungs. 

The cylinder head is a vital part of your engine. If the engine block is the heart, the cylinder is the lungs.

The cylinder head can also be a means to extract more power from an engine, but how? You may have heard of the art of porting and polishing, but just what is it, and how does it equate to more power? 

In a normal everyday car, the engine is built to do one thing: function. It’s not a racer, it doesn’t have peak performance in mind, it just has to work.

As such, the ports within the cylinder head are simple chambers that carry air and fuel in and exhaust gasses out.

This is because a standard engine is built with longevity in mind, and as such, is engineered well within the desired tolerances. In laymen’s terms, that means there is room for improvement.  

What is cylinder head porting and polishing?

The ports will be rough. This is a result of the casting process. This also means it becomes a turbulent environment for the gasses being passed through them.

The rough ports disrupt the gasses and impede their ability to flow. So what can you do to counter this? Well, you can polish them.

Polishing the ports is the art of using specialist grinding equipment to smooth the port walls. The smoother they are, the less disruption for the gasses, so they can flow more freely and as such, they can flow faster, both in and out.

That means air and fuel can get in faster, while exhaust can be pushed out more quickly, too. This of course means an increase in performance. 

Then there is porting. This is where a specialist looks at and the port shape overall and then uses the same specialist grinding equipment to ensure there are no hard corners, or other obstructions that may cause issues for the gasses. This is a highly specialised job.

The technician will subject the cylinder head to a flow test first, and then with the results to hand, they will be able to enhance the ports. This also makes the ports bigger in turn, and bigger means more fuel and air, and more fuel and air mean more power. 

What is cylinder head porting and polishing?

On its own, porting and polishing isn’t going to dramatically change the way your car drives. It might free up a few ponies, but that’s it.

Think of porting and polishing as a modification to enhance an engine build overall.

So, if you change the camshaft, the fuelling, the valves, then porting and polishing will further enhance their abilities.