A Definitive Guide to Port and Polished Engines

More air and fuel in the cylinders translate to more horsepower. This is why a lot of gearheads resort to installing forced induction systems like turbochargers and superchargers to make their vehicles faster.

But aside from these systems, there’s another way to unlock an engine’s maximum horsepower. This process is known as engine porting.

What Is Engine Porting?

Engine porting, also referred to as “port and polish,” is the process of smoothing out any form of obstruction that can restrict airflow in the cylinder heads. It’s as old as performance engines and has been done for many decades.

This process involves grinding out bumps, chamfers, and rough edges in the intake and exhaust passageways, cylinder heads, and manifolds.

Polishing these passageways lets more air and fuel enter the combustion chamber, resulting in increased horsepower of up to 10%.

That being said, some newer engines have manifold tuning plates operating in each runner all mounted on a rotating shaft so they can actually close to restrict airflow during periods of idle and low speed. These plates will have a “bite” out of one corner to let a bit of air to pass even when they’re closed.

Some newer engines have manifold tuning plates operating in each runner all mounted on a rotating shaft so they can actually close to restrict airflow during periods of idle and low speed.

– Richard McCuistian, ASE Certified Master Automobile Technician

This kind of manifold tuning actually causes the air entering the cylinder to speed up on the way into the combustion chamber, which provides better combustion chamber turbulence and flame propagation. The restrictor plates will open wide during wide open throttle events to allow maximum airflow into the cylinders.

The Need for Porting and Polishing

The casting process for cylinders can result in a cast flash. This is a defect that results from metal leaks in the cast, which seeps into the base of the mold and material when the metal is in its molten state.

After the casting process, machining methods will mill out the valve seats, chambers, and other parts to form the cylinder head design.

The result is a rough cylinder head that might require porting and polishing.

How to Port and Polish Heads

Removing as little material as possible is important when porting and polishing. Airflow is more sensitive to shape rather than size, so over-enlarged ports won’t produce the results you’re looking for.

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Pro Tip: The intake ports must be ported to exactly match their respective ports on the head. Many engine builders have a template similar to the gasket for marking both sides before porting begins.

Grinding out the ports is also a meticulous process. Overdoing it can weaken the cylinder heads, resulting in leaks or cracks.

To begin, you’ll need a port and polish kit, which usually includes tapered rolls, cylinder rolls, and mandrels that are attached to an electric or pneumatic die grinder.

Head porting is essentially the method of using motorized sandpaper to reduce restrictions in passageways.

Although it sounds like a job that a DIYer can do in their own garage, it’s always a good idea to seek help from a certified mechanic before proceeding. Doing so can minimize the risks of damaging other parts and getting unwanted results.

It’s also important to know the material you’ll be dealing with. For example, aluminum heads abrade faster than cast iron, so you might have to take additional precautionary measures when porting and polishing.

Precautions When Porting and Polishing

Aside from having the right tools, you should also observe safety protocols when porting and polishing.

Because you’re dealing with metal parts that could fly around while you’re working, it’s important to wear a pair of safety goggles, a dust mask, and gloves.

Avoid wearing loose-fitting clothing and jewelry. You’ll be dealing with a high-speed die-grinder, so it’s also best to tie your hair if it’s too long.

What to Port and Polish

Rough casting, unmatched passageways, and roadblocks in the combustion chamber are the three main restrictors of airflow.

The good news is that porting and polishing the cylinder heads can resolve some of these issues.

Here are some areas you can port and polish to improve airflow.

Exhaust Ports

The highest velocity of air that exits the cylinder is found in the exhaust ports. In most cases, material is shaved from the top of these ports.

Exhaust ports can also be matched with the exhaust manifold to improve airflow.

Inlet Ports

Polishing inlet ports removes ruts and metal particles that were produced during the casting process.

However, keep in mind that there should still be some roughness in the inlet ports to let fuel deposits on the port sides evaporate.

Combustion Chamber

Polishing the top of the combustion chamber can help create a smooth passage for the combusted air/fuel mixture and pass through the exhaust manifold.

Valve Throat Pocket

The valve throat pocket is one of the most important areas to smoothen out when porting and polishing to maximize airflow. In most cases, this area contains rough edges and chambers as a result of factory machining.

Valve Seat

Porting and polishing the valve seat improves the engine’s volumetric efficiency because it creates an exact seal with the valve when closed.

Trade-Offs When Heads are Ported and Polished

Having expanded ports sacrifices torque output in the low rev range because of decreased fluid velocity. However, power gains can be observed high in the rev range because a larger volume of air and fuel make their way into the cylinders.

FAQs About Porting and Polishing Heads

Here are some frequently asked questions (FAQs) about porting and polishing cylinder heads.

Can you port and polish at home?

Yes. There are several port and polish kits you can buy in your local supplies store, and you can work on your vehicle in the comfort of your garage.

How much does it cost to port engine heads?

$200 is a decent price to pay if you’re looking to port your vehicle’s cylinder heads. This is a common price point for a three-angle valve job.

But if you’re looking to get big valves and a bowl-porting job, you can expect to pay anywhere between $500 to $700.

Will a port and polished engine consume more fuel?

No. Porting and polishing won’t necessarily reduce your vehicle’s fuel economy.

Key Takeaways

Porting and polishing is a cost-effective method that helps improve your engine’s horsepower. By smoothing out rough edges and ruts in the ports, valves, and combustion chamber, air is able to flow properly, leading to a more efficient fuel combustion process.

Porting and polishing only requires a few tools, but it’s a meticulous process that should be done by professionals. If done incorrectly, your vehicle is at risk of developing cracks and leaks.

Experienced DIYers can do this task in their own garage, provided that precautionary measures are observed and they have the right tools.

Lastly, there are some trade-offs when porting and polishing an engine, but overall, you can expect to see some improvements in terms of performance.

Where to Get a New Cylinder Head for Your Vehicle

While engine porting is a great way to prolong the lifespan of cylinder heads, there are cases when porting isn’t enough to save them. In this scenario, it’s best to look for a replacement cylinder head instead of clinging to the small chance the old one can power through and work as intended. Thankfully, you can easily get a replacement with the help of CarParts.com.

The first step in choosing a replacement piece is looking for one that’s compatible with your vehicle’s specifications. Our website makes checking for fitment easier thanks to our built-in vehicle selector. This tool lets you sort our catalog based on your vehicle’s exact year, make, and model.

All engine components in our catalog were sourced from today’s top parts manufacturers. While we stand by the quality of these parts, we accept returns within 60 days of purchase and offer a lifetime replacement guarantee for qualified products.

Got questions about your order? Our lines are open 24/7 to answer any questions you may have about our products.

Shop and order your new cylinder head today!