Collection: 4G63 500-700whp

We provide a variety of specialized services designed to optimize your cylinder head for peak performance. Below are the services available for the 500-700whp range.

Power Pak 2
Maximize Your 4G63's Performance
Our Power Pak 1 includes premium parts and expert services to elevate your combo.
Included Services and Parts:
- We use your supplied core: Cleaned and inspected with reliability and performance in mind.
- GSC Power Division Valves: Stock size for durability and optimal flow.
- GSC5098 Conical Spring Kit: Superior valve control under extreme conditions.
- Services included:
- CNC Pocket Port: Includes disassembly, cleaning, CNC Pocket Port, GSC bronze guide installation, precision valve job, milling, and professional assembly.
Power Pak 1 delivers unmatched performance and reliability for 500-700whp. This package is designed to be used with no more than a advertised duration of 272 for ultimate performance in a street car. Contact us to get started!

Aftermarket Refresh
Our 4G63 Aftermarket Refresh service ensures your aftermarket valvetrain is optimized for peak performance. Here’s what’s included:
Included Services:
- Disassembly & Inspection: We carefully disassemble and inspect every component.
- Spring Height Check: Verification of your aftermarket spring kit’s height for proper functionality.
- Valve Inspection: Detailed assessment of all your aftermarket valves.
- Valve Job Touch-Up: Precision adjustments to improve sealing and flow.
- Milling & Assembly: A fresh sealing surface and professional reassembly.
Important Notes:
This service is subject to compatibility. If the valvetrain components in your cylinder head do not meet our specifications for safe and reliable operation, we may decline assembly to ensure quality and performance standards.
Give your 4G63 the refresh it deserves. Contact us today to learn more!

Pocket Port
Pocket Port: The Perfect Upgrade for 550-700whp Builds
If you’re making 500whp to 700whp, a full port isn’t just unnecessary—it can actually hurt performance by increasing port volume too much, reducing efficiency under the curve. That’s why we created the Pocket Port, a cost-effective solution that focuses on reshaping and resizing the critical valve pocket area and leaves the port alone to enhance flow where it matters most.
The Benefits:
More area under the curve and the ability to make power at lower, safer boost levels, keeping your setup efficient, reliable, and performing at its best.
Services Include:
- CNC Pocket Porting: Disassembly, cleaning, and CNC precision porting to optimize flow.
- GSC Power Division Bronze Guide Installation: New bronze guides and seals expertly installed for enhanced durability.
- HG Precision Valve Job: Restores sealing and maximizes airflow for consistent performance..
- Milling: Provides a flawless surface finish for proper sealing.
- Professional Assembly: Assembled with expert care for ultimate reliability and performance.
Not All Parts Are Created Equal—Here’s How We Pick the Best for Your Build!

Valve Upgrades
Why Aftermarket Valves Are Essential
At this power level, upgrading your OEM valves is a must! Aftermarket valves are built with high-strength materials designed to withstand the extreme heat and stress of high-performance applications. While aftermarket valves may bend under extreme conditions, OEM valves are more likely to break—making aftermarket valves the safer, more reliable choice.
Is Bigger Better?
Not in this case! We don’t install oversized valves in Subaru engines because they’re unnecessary. In fact, we’ve achieved 1400whp on stock-size valves.
Fun Fact: If your cam has less than 10mm lift, oversized valves can actually reduce performance. Bigger isn’t always better—it’s about using the right components for maximum efficiency and power!

Spring Pressure Considerations
A common concern when selecting a spring kit is adding too much spring pressure, particularly for street applications. However, when it comes to spring pressure, more is generally better than less. Insufficient pressure can lead to valve float, which can cause significant damage to your engine. Proper spring pressure ensures stable valve control and prevents potential issues at higher RPMs.We recommend a minimum of 85lbs seat pressure and 225lbs open at this power level.

Importance of Correct Valve Spring Pressure
The right amount of spring pressure ensures the springs remain controlled, which in turn keeps the valves functioning properly. The number one cause of valve-train or cam/bucket failure is using the wrong valve spring for your application. If the valve spring isn’t up to spec, nothing else in the system will perform at its best. Proper spring selection is key to maintaining reliability and preventing costly damage.

Choosing the Right Camshaft
Planning to relax in a lawn chair and listen to your car? If so, you might be tempted to go for the biggest cams on the market, and while it’ll certainly make your car sound great, it could also make it feel laggy. A camshaft that’s too large can deliver the sound you’re looking for but at the cost of drivability, especially in terms of throttle response and power delivery. Choose a cam that matches your performance goals for the best balance between sound and feel.

The Best Cam for Your Boosted Adventures
If you love pushing your car to its limits and diving into boost on the street, a smaller cam is the way to go! For builds between 550-700whp, GSC Power Division S1 cams are the perfect upgrade. GSC Power Division for 700+builds.
These cam choices deliver plenty of area under the power curve, ensuring smooth, reliable performance that keeps your car pulling hard and your smile wide for miles of boosted fun!
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