DIY tips in porting and polishing cylinder heads

Updated Dec 31, 2020 | Same topic: Tuning & Mods

Increase your car’s horsepower without spending a huge amount of cash.

I. What is porting and polishing?

When car manufacturers make engines, they don’t get them perfect all the time despite the advancement in recent years. But of course, these engines won’t go out to dealerships if they aren’t working to their prescribed working specifications.

Since cylinder heads are made up of cast aluminum, it is not a surprise to find castings on their ports whether on the intake or exhaust. The ports on the exhaust tend to come with more irregularities as they are the gateway of exhaust gases.

A car's cylinder

See those oval-shaped holes? Those are the cylinder head ports

The irregularities or castings will disrupt airflow whether going to the combustion chamber or out to the exhaust manifold. As such, the expected output will not be as powerful as an engine produces more power with higher amounts of fuel/air mixtures.

This is where porting and polishing comes to the scene. In simple terms, porting is the process of enlarging a port so that more air can be pumped into the combustion chamber. Meanwhile, polishing is the process of smoothening out the ports so air can efficiently flow to and out of the combustion chamber.

Both of these processes have been around in the automotive scene since the 60s. In consideration of how porting and polishing sound, they can be a bit tricky in the application as the ports are essential in efficiently supplying fuel/air mixture to the combustion chamber. But if you could do the processes by yourself at home, then you could save a hefty amount of cash.

II. Why you should consider porting and polishing cylinder heads?

Car owners have been thinking of various ways to make their vehicles go faster. Some of these include installing a turbocharger or supercharger, buying performance tires, equipping their car with new suspensions, and fitting lighter materials such as carbon fiber.

All of the said modifications do cost a lot. Some would think it is just fair to do so, while some would think that it is impractical. Porting and polishing are two processes that can make your car go faster without spending a huge amount of cash but costs a lot of your time though.

A motorcycle engine

Porting and polishing can be done on motorcycle engines as well

Porting increases the amount of air that can be inducted into the combustion chamber due to larger ports. The more air, the more power your engine can produce. This then results in more horsepower. Porting is a simple way to have a horsepower bump at home.

Meanwhile, polishing goes hand-in-hand with porting. Since castings on ports cause turbulence, less air is taken into the combustion chamber. Well-polished ports help the air flow smoothly and more efficiently to the combustion chamber.

Car moving fast

A costless way to increase the horsepower of your car

Try to think of cylinder head ports as rocks. They come with rough surfaces normally felt when touched. Using polishing tools such as sandpaper or stone can smoothen out the rough surfaces. Polishing will also increase the horsepower of your engine just like with porting. You should consider doing these processes if you want a more efficient airflow within your cylinder heads that results in higher power output.

Of note, porting and polishing takes time. The maximum would be two days if working consistently. But can be done in a day depending on familiarity. You can ask for a friend who knows how to port and polish a cylinder head so you can avoid further damage.

>>> Related: 6 steps to increase the power of four-cylinder car

III. DIY tips in porting and polishing heads

You should use the proper tools as you will be working with a very essential part of the mechanism of your car’s engine. The most important tool for porting and polishing heads is a rotary tool. You can use a drill if you have one at home. However, we recommend using a Dremel rotary tool since it is lighter and more compact as compared to a drill.

Another tool you need is a caliper tool. There are digital caliper tools available as well if you aren’t sure how to read a conventional caliper tool. This will help you measure the size of your cylinder head and intake manifold ports. Theoretically, if the sizes of the ports of your cylinder head and intake manifold are identical, then the air will flow more efficiently.

A yellow drill

A rotary tool is a key component so you can finish the job faster

The last tool you will need is either a sandpaper or stone drill bit. We recommend that you use safety goggles as you will be removing castings on the ports of the cylinder head. 

The first step in porting is to measure the size of the port using your caliper tool. Be sure that you will always consider the port sizes of your cylinder head and intake manifold before enlarging the ports. Remember that porting takes a lot of time so you should be careful not to reshape the ports. The ports should retain their oval-like shape for optimum operations.

A folded sandpaper

Sandpapers can do the job as well, but not as efficiently as a rotary tool

After porting, you should now move to the next step which is polishing. You can either use a Dremel rotary tool or just sandpaper to smoothen out the ports. There are two spots you can start polishing, namely in the combustion chamber area and the intake manifold area.

When polishing, your sense of touch is more important than your sight. What you see can be deceiving especially when polishing in a poorly lit working environment. Get a feel of the ports and make sure that the ports feel smooth so air can flow more efficiently.

>>> Related: Top 10 improvements in car engine design

IV. Porting and Polishing Cylinder Heads: FAQs

Q: What is the benefit of porting and polishing?

The biggest benefit in porting and polishing your car’s cylinder head is it increase your car’s horsepower since more air will be inducted into the combustion chamber.

Q: Can I do porting and polishing by myself?

Yes, porting and polishing are some of the DIYs you can do even in the comfort of your home.

Q: What tools for porting and polishing heads do I need?

You would need a rotary tool, caliper tool, and sandpaper or stone drill bits.

Q: Are porting and polishing expensive?

They are expensive if you take your car to a local automotive shop. However, you can do it at home if you already have the prescribed tools.

Q: How long do porting and polishing usually take?

Porting and polishing usually take a long time to finish. You would normally finish porting and polishing for two days. It can take three days or just one day depending on how much time you put in and your familiarity with the processes.

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Rex Sanchez

Rex Sanchez


Rex Sanchez grew up in Saudi Arabia where he saw and got into the automotive scene. He started his career for an aviation company in the said region, writing about turbines and rotors which are later distributed for educational purposes. And now, he joined as a staff writer. Currently, he is the youngest on the team and is more than ready to grow in the field.


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