Rotary Engine build Blog

Building the Rotary Engine is all in the right tools, experience and knowhow. Get it right


9 Min Read

Rotary Engine Builds | U can have it cheap or done right.

Rotary Engine Builds | Going from medium to wild w/ reliability


Mazda REbuilds in Colorado | March is around the corner, spring will soon be here.


Mazda Rotary Engines | Brap, Brap!Rotary Engine Shop Colorado

Projects are starting to line up and people are ready to get out and about.

People want their cars to perform well here at 5000 feet (at minimum). Increasing power is a reasonable goal providing that you start with a proper build. 

Details matter. When you bring your Mazda in for the first visit, what are the first steps? We are a specialty shop with performance results always on tap. From strong motor builds to sequential transmission upgrades to off road fabrication, we do a lot more than bolt on parts, we build performance vehicles.

Expectations, where are you at with regard to horsepower, drivability, and overall condition? 

Mazda Rotary Engine upgrades | We start with a basic compression test and go from there.

If for any reason the pulses are inconsistent and even within limits, we tear it down. Why build up the turbo or NA system to make more power when the motor is weak before we even get started? This is common with most shops who can't wait to bolt up a larger turbo and get on the dyno.

When it is determined to take out those 17-19 long bolts and crack the seals on those housings, things get busy and extremely detailed.

That means going from stock with a few bolt ons to going inside the motor for more power, improved breathing, oil flow / efficiency, etc. The first step with every rotary engine that comes in for a teardown / rebuild is painstakingly more than a few minutes. Time for the good measuring equipment to show the way.

The number of points to measure inside a rotary engine is a lot. We take 3-4 hours to know precisely what is going on inside down to the ten thousandth of an inch (or metric if you prefer), because a proper motor is the only way to go. When I hear a potential customer tell me that they want the minimum to make it work and want more power, a major red flag. Of course money matters, I'd rather do it once than both of us be disappointed.

Mazda Rotary Engine Builder Colorado | You can have good work, you can have cheap work, choose carefully.

I like to teardown the motor from a motor that is still bolted up. Please do not bring a motor that you have taken apart already. There are a lot of clues to how it ran during the time of pulling plates and parts. That means looking at how the seals react, do the seals spring out, or are they stuck? Is there a lot of coolant residue, how to the passages look?

After taking apart 100’s of rotaries, the way in which it plays out demonstrates how the motor was last operated. Just because it failed, doesn’t mean you have to start all over with new parts everywhere. 

engine rebuildsOf course when we get it all separated, then is the time to clean and start measuring. It is important to take time and clean off surfaces (without reducing material) to get a good measurement. I like to use scotchbrite to prep the areas of measurement, taking dubious notes is critical for making the right decisions (rebuild or replace parts). 

  • Pictured here, eccentric shaft measurement, they do bend with repeated twisting past redline, get it right. 

  • When we pull the main bearings, often we see the front bearing wear out on one side, that is due to over tightening the AC belt. (see bearings above).

I’ve seen 12A motors that sat for 20 years look great on the inside and used 80% of the parts for building a competition motor for vintage racing. I’ve also seen many 13B motors that were a daily driver where there was very little to be used (and it ran when it came into the shop) because it was abused, run hot and someone missed a few too many shifts. Details matter.

We love to rev our rotary motors to the limit, ripping the rear tires and pushing these cars hard, that is where the excitement is. Start a conversation, get the results that lead to miles of smiles / grins. It is your money.


Topics:   rebuilds

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