4P Pro R40 K24Z CNC Cylinder Head

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  • Regular price $1,350.00
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The NEW Pro R40 CNC cylinder head is the ultimate cylinder head for your K24Z powered street or race car.  This platform has long been neglected due to a lack of camshaft and valvetrain availability, and the single port exhaust design that has been touted as an Achilles heel when compared to traditional 4 port K20 cylinder heads.  It is true that this presents some challenges when building a maximum output high rpm platform, but it also presents some great opportunities.  The intake port from the factory stock R40 is actually the best flowing K-Series port that Honda has produced to date, and we drastically improve on that.  The exhaust may appear to be a challenge, but it can be exploited as a great opportunity for many users.  This head design makes turbo packaging much easier, and reasonably sized turbos in the 500-850whp range respond and spool very fast.  This R40 cylinder head arrangement is also preferred in some RWD applications for its superior packaging.  You may be a person that doesn't want to tackle the challenges of swapping to a 4 port head, and this CNC Cylinder head lays the ground work for you to make more power than you can ever use effectively.

We take the R40 Cylinder Head casting and CNC port the intake ports and critical bottleneck areas of the exhaust port.  This includes the bowls and short turns, and a major rework of the exhaust outlet.  Areas of the port that are close to water jackets are left alone to prevent cracking with high exhaust temperatures and big boost loads.  Once the head is CNC ported, we finish it off with a fresh surface and our Newen single point CNC valve job.  We also offer our own PAC valve spring setup that is far superior in valve control and longevity than preexisting offerings.  4P Camshafts are in production, with delivery expected late 2021.

Send your R40 head casting for us to port, or purchase our cores outright without having to send one in.


  • CNC Ported intake and exhaust ports
  • OEM Guides left in for porting or OPTIONAL Bronze valve guides
  • Precision CNC valve job using the latest NEWEN Fixed Turning technology
  • Resurface

Recommended Use

  • All Motor Street/Race
  • Turbo Street
  • Road Race and Time Attack

Features & Benefits

  • 370cfm airflow where popular camshafts lift, and huge low end and midrange flow.
  • Slow-cut precision 5-axis cnc porting, second to none on machining quality.
  • 45 degree valve job designed for long life and durability.
  • Unique power producing exhaust port design.
  • Optional Full length bronze manganese valve guide for valve stability.
  • Port walls are left extra thick for high boost applications.
  • Our heads are all shipped with installation tips, a sheet of desired clearances for setting up your engine, and a flow chart from your head.

All heads require a core! You can send us your head, or purchase one from us at the current market price.

See our 340hp R40 head and cam test below, all motor, pump gas.  We changed induction and made 356 the next day!