Power Pak's just the beginning - scroll on to uncover the how, the why, and everything you need to know to make game-changing decisions!

EJ Power Paks

Disassembly and Inspection

We take the disassembly and inspection process very seriously to ensure the highest quality. Each cylinder head undergoes an initial inspection during disassembly, followed by a second inspection by a separate technician to catch any potential issues right from the start.

Even if you provide new cores or disassembled heads, they will still need to be inspected for damage, unless purchased directly from HeadGames. Inspection fees apply to all cylinder heads.

  • For assembled heads, a $250 service charge covers disassembly, inspection, oil plug removal, and flushing in our Ultrasonic, and Wet Blaster. 
  • For disassembled and new cores, a $75 inspection fee applies. Remember, new heads can have issues too!

Cleaning

We’ve put in the effort to deliver the highest standard of surface finish and cleanliness in cylinder head cleaning.

For a factory-fresh look, we offer vapor honing to restore your heads to a like-new appearance.

All heads are thoroughly cleaned using our Wet Technologies wet soda blaster, ultrasonic cleaner, or spray washer to ensure optimal results.

Refresh and Restore Your Heads

We offer a range of specialized services to ensure your cylinder heads are optimized for performance, whether you're restoring or upgrading. Below are the services you can find in the 300-500whp and 500-700whp.

Starting with our Refresh Service, we'll get your heads running like new by cleaning, re-facing valves, refreshing valve seats, setting valve lash, milling, and assembling with new viton valve seals. If your heads are already built, our Aftermarket Refresh provides the same benefits for heads that need a little extra attention.

For more serious performance upgrades, our Rebuild with Guides Service installs bronze guides, ensuring proper valve-to-guide clearance for durability when installing an aftermarket valve.

Performance Upgrades for Serious Power

Looking to make more power? We have you covered! These services are available in the 700-900whp and 900+whp range.

Our Pocket Port Service offers a cost-effective way to enhance the area under the curve, especially for builds in the 500-700 WHP range, all while keeping your boost levels in check. Finally, if your budget allows, our CNC Port Service is the ultimate upgrade, providing up to 140 WHP gains in the mid-range, faster spool time, and unmatched reliability.

Oversized Valve Flow vs. OEM Valve

We only install OEM-sized valves in Subaru EJ heads, and here's why: The oversized valve is only .004 in inches smaller than the OEM valve seat, which is just .003 in inches thinner than a $1 bill. The valve seat functions as a heat sink, helping dissipate heat from the valve. Using an oversized valve in this application compromises the heat-dissipating properties of the valve seat, which can negatively impact performance and durability.

Oversized valves actually flow less than OEM-sized valves up to 9mm of lift. Consider this: most cams we install have around 10.5mm of lift, meaning you’re limiting flow for 90% of the cam’s lift range. In contrast, OEM-sized valves provide better flow where it's most needed, resulting in a greater area under the power curve. This translates to more consistent power, perfect for daily boosted performance and reliability!

Subaru EJ20/25

  • EJ20/25 Add-on Service

    We specialize in precision machining of the EJ20 combustion chamber to seamlessly fit the EJ25 short block. Using our cutting-edge Centroid 5-axis CNC, we deliver unmatched accuracy and consistency. Our process includes expertly softening the combustion chamber while retaining the OEM chamber volume for the B25 casting. This allows for running more timing, reducing exhaust gas temperatures (EGTs) on pump gas—enhancing performance, efficiency, and reliability. Trust us to deliver tailored solutions that optimize your engine’s potential and take your build to the next level.

    For HeadGames to perform this service, it must be accompanied by, at minimum, our refresh service. This is because the head must be fully disassembled and cleaned before the work can be carried out. We will not reassemble the head without addressing key components, including touching up the valve job, thoroughly cleaning all parts, and refacing the valves. This ensures the highest level of quality and performance in every service we provide.

  • EJ20 Cracks

    The EJ20 (S20) cylinder head castings are notoriously prone to cracking in the combustion chamber. These cracks typically run from the spark plug to the valve seats on both sides and can also extend down the spark plug hole. Unfortunately, there is no permanent fix for this issue aside from replacing the heads entirely.

    As a rule of thumb, we classify these heads as unusable ("junk") if the cracks extend more than four threads down the spark plug hole. This is done out of caution, although we’ve never experienced a failure with heads exhibiting these cracks. In fact, we’ve worked on and made over 800whp with these heads without issue. That said, we cannot offer any guarantees for this casting.

    Using these heads is entirely at your own risk, as the cracking is a known flaw inherent to the OEM design.