Getting the Most From 91 Octane Pump Gas with a Honda K Motor, Part One

The stock K24 crank is a high quality forged piece and we use it.  We chamfered the oiling holes, deburred it, then sent it out for mangaflux to check for cracks, balancing, micro polishing the journals then WPC treatment.


As with many of our builds, we used Kings XP rod and main bearings.  We have had extremely good luck with these bearings. The XP bearing uses Kings P-Max black tri-metal construction a steel backing is covered with a hard intermediate layer with a high tin and copper content for superior load-bearing capacity. This is covered with an overlay with a 2-3% copper content which is harder than typical for excellent load-bearing capacity.  This intermediate layer and overlay result in a bearing with 24% more load capacity and 17% more fatigue resistance than its competitors.

King XP bearings are coated with their pMaxKote.  pMaxKote is a ceramic nanoparticle enhanced polymer coating.  The coating provides increased wear and seizing resistance while increasing the bearing’s load capacity.  We have torn down some long term race motors that have run this coating and were amazed to find the bearings looking like new.  The upper main bearings that are grooved have King’s U-Groove oil groove design, this design has a deeper but more narrow oil channel that allows for good oil distribution while giving more bearing surface area for better load-bearing capacity.

King Bearings use an eccentric profile for a better hydrodynamic oil wedge formation. The bearings also use King’s radial lock method to provide a better press fit for more spin resistance and better heat transfer from the bearings surface without bearing surface distortion in the area where the shells come together. We used King Part Numbers MB5259XPC STD and MB5259XPC.026 for the main bearings and CR4542XPC STD and CR4542XPC .026 for the rod bearings.

While we were sending stuff out for WPC treatment, we sent out the oil pump gear as well.  This improves this critical part’s strength and reduces friction to reduce oil heating while pumping.


  1. Just wondering something: Why do you always choose the K24 bottom end in the states? Is that just for the longer stroke and therefore more displacement?

    Assuming a K20 bottom end is the same, why not build a K24 bottom, with K20 bottom internals and longer conrods? (because the deck height is 19,5mm taller on the K24 engine). Smoother running and more RPM potential? Redline should theorectically be around 12000 RPM that way, and smoother running because of the smaller stroke? Sure, you loose a bit of torque that way, but you would gain top end power if you use the RPM potential with a high duration cam.

    Or am i not seeing something here?

    1. You make good points here, but I think in a street engine, spinning to 12k rpm is not feasible. If you can make more power at a lower rev range, and still have the ability to make power at 8000rpm why bother?

      1. Meh, depends on how you build something. I had a pet project that was stolen years back: A-series engine. The BMC/Rover/Austin/Morris/MG one.

        Long story short: 1046cc OHV engine (designed with 3 crank bearings in the late 1930’s as a generator on the back of a tank), capable of 12.000RPM (Normal is about 5500 RPM) Stil normally drivable. Even legal to drive with emissions here in Europe. Idled at 800 RPM without being overly lumpy. Although I must admit that it was running on BP Ultimate 102 RON.

        In a way its compairable to an S2000. Just a regular engine down low until it wakes up once past 4500 RPM really. My point being: RPM limit at which an engine makes power does not neccesarily mean it’s a mut down low. Its just a different mindset when driving it. It isn’t as lazy driving as a bigger displacement engine though. So it would be feasable, but the biggest concern is going to be to find hypereutectic pistons that can handle the stress. Forged aluminum just expands to much. You either get a pinching engine op high, or burning oil if the engine is starting up.

        And to answer your question: For me its always the challenge of building it. But it is a lot harder to do it right once you start using it in day to day life.

  2. JE piston makes nice products but their website is not one of them, it’s top notch web design from 1998 and filled with outdated/missing information.

    I learned through e-bay that they now make coated asymmetrical pistons for BPs because JEs website still lists that piston as an uncoated round skirt.

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