Cylinder head porting is one of the most effective—yet least understood—performance modifications you can make to an engine. While bolt-on parts like intakes and exhausts get all the attention, the real power is made in the cylinder heads. Porting optimizes the airflow passages inside the heads, allowing the engine to breathe better and make significantly more power.
After building hundreds of engines with ported heads here at Raw Exotics, I can tell you that good port work is worth every penny. But there's a lot of confusion about what porting actually is, what it costs, and when it makes sense for your build. This guide breaks down everything you need to know.
What is Cylinder Head Porting?
Cylinder head porting is the process of reshaping and smoothing the intake and exhaust ports inside the cylinder head to improve airflow. The goal is to remove casting imperfections, enlarge restrictive areas, smooth rough surfaces, and optimize the port shape for maximum flow efficiency.
Think of it like this: air flowing through your cylinder head is like water flowing through a pipe. If the pipe has rough spots, sharp corners, or restrictive sections, water flow is reduced. Smooth the pipe, round the corners, and enlarge tight spots, and water flows much faster. The same principle applies to airflow in cylinder heads.
Why Porting Matters
Your engine makes power by burning fuel and air. The more air you can flow through the engine, the more fuel you can burn, and the more power you make. It's that simple.
Factory cylinder heads are mass-produced using sand casting. This process leaves rough surfaces, inconsistent port shapes, and imperfections that restrict airflow. Manufacturers accept these imperfections as a cost-saving measure—hand-finishing every head would be prohibitively expensive.
Porting removes these restrictions. A well-ported head can flow 15-30% more air than the stock head, which translates directly into more horsepower and torque.
Types of Port Work
Not all port work is created equal. There are several levels of porting, each with different costs and power gains.
1. Port Matching (Entry-Level)
Port matching is the simplest form of porting. The ports in the cylinder head are matched to the intake manifold and header flanges to ensure smooth airflow transitions.
Process: Use the intake manifold and header gaskets as templates. Grind the head ports to match the gasket openings, eliminating steps or lips where air could be disrupted.
Power gain: 3-8 hp. Minimal but worthwhile during any head removal.
Cost: $200-500 depending on engine and labor rates.
Best for: Budget builds where every small gain counts. Should be done anytime heads are off the engine.
2. Gasket Matching + Cleanup (Basic Porting)
This level includes port matching plus cleaning up obvious casting flaws, smoothing rough spots, and removing sharp edges in the ports.
Process: Port match the openings, then use carbide burrs and sandpaper rolls to smooth the ports, remove casting flash, and round sharp transitions.
Power gain: 10-20 hp depending on how rough the factory heads were.
Cost: $500-1,000.
Best for: Mild street builds looking for cost-effective gains.
3. Bowl Blending and Pocket Porting
Bowl blending focuses on the area around the valve—the short side radius and valve bowl. This is where the majority of flow restriction occurs in factory heads.
Process: Blend the short side radius (the curve from the port floor up to the valve seat), reshape the valve bowl for smooth airflow, and optimize the valve seat angles.
Power gain: 20-40 hp. This is where you start seeing significant improvements.
Cost: $1,200-2,000.
Best for: Serious street builds and entry-level race engines. Best bang-for-buck in terms of flow improvement.
4. Full CNC Porting
CNC porting uses computer-controlled machining to shape ports to exact specifications based on proven designs. This is the highest level of port work available.
Process: The entire port is reshaped using a CNC machine following a program developed through extensive flow bench testing and research.
Power gain: 40-80+ hp depending on the platform and how restrictive the factory heads were.
Cost: $2,500-5,000+ depending on the platform and shop.
Best for: All-out race builds, forced induction applications, and serious naturally aspirated builds where maximum airflow is critical.
5. Competition-Level Hand Porting
The ultimate in port work—a skilled porter hand-shapes every port for maximum flow, often exceeding CNC capabilities in certain areas.
Process: Highly experienced porter uses flow bench testing to develop optimal port shapes, then hand-grinds each port to maximize flow while maintaining velocity.
Power gain: 50-100+ hp on serious builds. The best hand-ported heads can outflow any factory or CNC head.
Cost: $3,000-8,000+ depending on complexity and porter's reputation.
Best for: Professional race engines where every CFM of airflow counts and budget is no object.
Understanding Airflow: CFM and Flow Bench Testing
When discussing ported heads, you'll hear people talk about "flow numbers" measured in CFM (cubic feet per minute). This is how much air the head can flow at various valve lifts.
Reading Flow Numbers
Flow bench results are typically presented like this:
- Intake @ 0.500" lift: 245 CFM (stock) vs 275 CFM (ported) = +30 CFM gain
- Intake @ 0.600" lift: 260 CFM (stock) vs 295 CFM (ported) = +35 CFM gain
- Exhaust @ 0.500" lift: 180 CFM (stock) vs 205 CFM (ported) = +25 CFM gain
More CFM = more air = more power. As a rough rule of thumb, each CFM of additional flow is worth approximately 2 horsepower on a naturally aspirated engine.
Example: LS3 Cylinder Heads
A stock LS3 cylinder head flows approximately:
- Intake: 315 CFM @ 0.600" lift
- Exhaust: 240 CFM @ 0.600" lift
A CNC-ported LS3 head flows approximately:
- Intake: 360 CFM @ 0.600" lift (+45 CFM)
- Exhaust: 270 CFM @ 0.600" lift (+30 CFM)
That 45 CFM intake gain translates to roughly 50-70 hp on a properly built LS3 engine with a matching cam.
Port Work for Different Engine Platforms
Different engines respond to porting differently. Here's what we typically see:
LS/LT Engines (Chevrolet)
LS heads have excellent factory flow, especially LS3/L92 rectangle port heads. However, they still benefit significantly from porting.
Stock LS1 heads: 210 CFM intake, 155 CFM exhaust
Ported LS1 heads: 250 CFM intake, 185 CFM exhaust
Power gain on LS1: 40-60 hp with matching cam
Stock LS3 heads: 315 CFM intake, 240 CFM exhaust
Ported LS3 heads: 360 CFM intake, 270 CFM exhaust
Power gain on LS3: 50-70 hp with matching cam
HEMI Engines (Dodge/Chrysler)
Gen3 HEMI heads (5.7L and 6.4L) respond extremely well to porting. The factory heads have significant casting restrictions that porting addresses.
Stock 5.7 HEMI heads (Eagle): 240 CFM intake, 175 CFM exhaust
Ported 5.7 HEMI heads: 285 CFM intake, 210 CFM exhaust
Power gain: 45-65 hp with cam
Stock 6.4 HEMI heads: 270 CFM intake, 200 CFM exhaust
Ported 6.4 HEMI heads: 320 CFM intake, 235 CFM exhaust
Power gain: 55-75 hp with cam
Coyote Engines (Ford)
Coyote heads are very good from the factory with DOHC design and four valves per cylinder. However, they still benefit from bowl blending and short side radius work.
Stock Gen2/3 Coyote heads: 290 CFM intake (per runner), 210 CFM exhaust
Ported Coyote heads: 320 CFM intake, 235 CFM exhaust
Power gain: 30-50 hp (Coyote heads are already very good)
VQ Engines (Nissan/Infiniti)
VQ heads have some of the best factory flow in the V6 world, but there's still room for improvement.
Stock VQ37VHR heads: 240 CFM intake (per runner), 175 CFM exhaust
Ported VQ37VHR heads: 265 CFM intake, 195 CFM exhaust
Power gain: 25-40 hp
When Does Porting Make Sense?
Porting isn't for every build. Here's when it makes sense and when it doesn't:
You Should Consider Porting If:
- You're building a naturally aspirated engine for maximum power
- You're installing an aggressive camshaft that demands more airflow
- You're building a dedicated race engine
- The heads are already off the engine for other work
- You've maxed out bolt-on modifications and want more power
- You're building toward a specific power goal that requires better flow
Porting Probably Doesn't Make Sense If:
- Your engine is stock or mildly modified (bolt-ons only)
- You're on a tight budget (porting is expensive)
- The car is a daily driver with no performance goals
- You're planning to go forced induction (boost masks flow deficiencies)
- The heads are currently installed and running fine (labor to remove them is significant)
Porting + Camshaft: The Winning Combination
Ported heads really shine when combined with a proper camshaft. Here's why:
An aggressive camshaft increases valve lift and duration, allowing the valves to open more and stay open longer. However, if the cylinder heads can't flow enough air to take advantage of that increased lift, you're leaving power on the table.
A well-matched cam and ported head combination is synergistic—the cam allows more valve opening, and the ported heads provide the airflow to fill that opening. The result is significantly more power than either modification alone.
Example: 6.4L HEMI
- Stock: 485 hp
- Cam only: 535 hp (+50 hp)
- Ported heads only: 540 hp (+55 hp)
- Cam + ported heads: 630 hp (+145 hp)
Notice how the combination produces more than the sum of the individual gains. This is the power of a matched combination.
Cost vs Benefit Analysis
Porting is expensive, so let's talk real-world costs and whether it's worth it:
Scenario 1: Naturally Aspirated Street Build
- LS3 Camaro
- Goal: 550 hp naturally aspirated
- Ported heads + cam + tune: $4,500
- Result: 550 hp achieved, car sounds amazing, reliable daily driver
- Verdict: Worth it for this power goal
Scenario 2: Budget Daily Driver
- 5.7 HEMI Charger
- Goal: "A little more power"
- Ported heads: $2,500 (parts + labor)
- Result: 40 hp gain, significant expense for modest improvement
- Verdict: Not worth it. Stick to bolt-ons and tune.
Scenario 3: Boosted Build
- Supercharged Mustang GT
- Goal: 700 hp with blower
- Question: Should we port heads?
- Answer: Probably not. The supercharger forces air through the heads regardless of porting. Better to spend money on intercooling, fuel system, and tuning.
- Verdict: Skip porting on boosted builds unless chasing 900+ hp
Choosing a Porter: What to Look For
Not all porting is equal. A bad port job can actually hurt flow. Here's what to look for in a cylinder head shop:
Signs of a Quality Porter:
- Flow bench verification: They test every head on a flow bench and provide before/after numbers
- Platform-specific experience: They've ported many heads for your specific engine
- Portfolio of work: They can show you previous work and customer results
- Realistic claims: They don't promise outrageous gains (be wary of "100 hp from porting alone" claims)
- Fair pricing: Competitive with other reputable shops (not dramatically cheaper)
Red Flags:
- No flow bench testing or verification
- Dramatically low prices (quality port work takes time)
- Unrealistic power claims
- No experience with your specific platform
- Can't provide references or examples of previous work
DIY Porting: Should You Try It?
Porting is often romanticized as a DIY project, but the reality is that it's extremely difficult to do well.
The Reality of DIY Porting:
- Requires expensive tools (die grinder, carbide burrs, sandpaper rolls)
- Takes dozens of hours per head for quality work
- Easy to make mistakes that hurt flow rather than help
- No way to verify results without a flow bench ($10,000-$20,000 for a quality bench)
- Risk of going too far and ruining expensive heads
Our recommendation: Leave porting to professionals. It's specialized work that requires years of experience to master. The cost of professional porting is justified by the expertise and flow verification you receive.
"Porting is where art meets science in engine building. It's not just grinding metal—it's understanding fluid dynamics, airflow, and how different port shapes affect power delivery. Good port work is worth every penny, but it has to be done right by someone who knows what they're doing."
Ready to Port Your Heads?
If you're building a naturally aspirated engine and want maximum power, ported heads are one of the best investments you can make. At Raw Exotics, we work with some of the best cylinder head porters in the industry and can help you choose the right level of port work for your specific build and budget.
We handle complete builds from short blocks to finished engines, and we'll make sure your ported heads are matched with the right cam, intake, and tuning to extract every bit of power. Call us at (713) 299-1168 to discuss your engine build.