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The Engine Swap Hall of Fame:
4-Rotor Mazda RX-7 FC Build

April 23, 2012 by Matt

4 Rotor Mazda RX-7 FC Build Project 2nd Gen FC3S 26B John Huijben RX7Club

This build isn’t even done yet, but the engineering and fabrication is so stunning that I feel compelled to feature it.

The skinny? It’s custom-engineered, 2.6l, peripheral port, 4-rotor Wankel engine transplant into a 2nd generation (FC) Mazda RX-7. Every piece is so jewel-like that it’s difficult to know where to begin.

John Huijben, an engineer and machinist based in the Netherlands, decided on a bit of a whim to put this engine together in his spare time. In his words, it’s more of an engineering exercise than anything else, and not meant to be a part of a fully integrated car. Put another way, it isn’t remotely the most practical or sensible way to build a powerful RX-7, but Lord help me if it isn’t absolutely fascinating. My kind of project, in other words.

4 Rotor Mazda RX-7 FC Build Project 2nd Gen FC3S 26B John Huijben RX7Club

Here’s the shell: a basic Series 4 (’86-’88) RX-7, a touch rusty, stripped down the degree it’ll have to be to accept the engine.

4 Rotor Mazda RX-7 FC Build Project 2nd Gen FC3S 26B John Huijben RX7Club

One of the build thread’s highlights is the CAD work. Stunning exploded views precede almost every major update and illustrate the benefits of careful design over a less thought-out, more improvised approach to engine building.

4 Rotor Mazda RX-7 FC Build Project 2nd Gen FC3S 26B John Huijben RX7Club

The slide throttle in particular is a complete work of engineering art. Less restrictive than a conventional butterfly throttle, especially at WOT, its design and implementation are peerless.

4 Rotor Mazda RX-7 FC Build Project 2nd Gen FC3S 26B John Huijben RX7Club

The part of the 4-rotor build that takes the cake, though, has to be the custom eccentric shaft (a rotary’s equivalent of a crankshaft). Instead of mating two e-shafts from smaller, 2-rotor engines, Huijben decided to design and machine his own custom piece from a solid steel billet (shown at top in photo above). Given its precise balancing, oiling and harmonics requirements, it’s a tour de force of engineering.

I’ll definitely be keeping up with the build’s progress. Can’t wait to see it come to life for the first time!

H/t to Aaron for the link to the build. Thanks!

Editor’s note: This post is part of an ongoing series showcasing awesome engine swaps and builds. Read the other installments here:

Filed under: Engine Swap Hall of Fame, Mazda, Rotary, Technical, Tinkering


  1. castor says:

    necesito saber si ustedes venden las sentricas para cuatro rotores me interesa almar uno grasias.

    • Matt says:

      Sorry, I don’t sell anything. Just wanted to share a great build thread.

      Have you checked or

  2. areopagitica says:

    If the Rotary engine had a future it was as a marine or aero engine, since it is unburstable and like to run wide open load at high rpm. Its form factor as a single rotor device would also make a fine end on fitting mostly constant speed motive power for a motor generator combo to juice up the wheel motors of an electrohybrid. Too bad the thing has fallen out of favor because of its thirst from torque curve liabilities that did not suit variable speed and variable load operation in a passenger car.

    • Matt says:

      Eh, I disagree, to a point. I concede the rotary’s disadvantages as developed, but I think that if automakers hadn’t (over)reacted so dramatically to the 1973 oil crisis that doomed non-Mazda rotary development, the powerplant’s downsides could have been overcome. So to me it’s not a question of the engine’s nature being bad so much as its nurture, so to speak.

  3. goto says:

    4rotor engineの事で、相談あります

  4. Devin McDougal says:

    Will he be selling copies of those 4 rotor eccentric shafts?

    • Matt says:


      Doubtful. But I suppose it wouldn’t hurt to ask. Heck, someone may have already asked the question somewhere in the 50+ pages of the thread.

  5. Patrick says:

    Where can I order the engine?

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