REspeed Rotary Engine Blog

Part 2 12A Engine Rebuild before it tears itself up

Written by MazdaDoug | Feb 23, 2025 2:30:01 PM

Part 2 Rebuilding the Rx7 12A with performance gains and reliability

Once we got the motor apart, remember this motor was running fine, drove nice and started hot and cold. The fact that I did not get to drive this car, I didn't notice it was low on power, it sound right, pulled to redline and didn't smoke.

My assumptions were not all accurate as once we got it apart, I thought a seal kit, some replacement of a few worn parts (oil pump / chain, the usual) and a few upgrades. Not so fast.

Like I tell everyone, we do not know what the motor needs until we get it apart, measured and ultrasonic cleaned. The big tell was looking at the lower compression area of the rotor housings, both of them had coolant leaking into them over time (inner seal giving way) and the chrome was flaking, reducing compression.

When we rebuild a motor, it has to be done correctly, I do not take shortcuts to save a few dollars. And, as I tell every customer, I do not want to see the inside of that motor for a long time.

As you can see by the pictures, the combustion chambers were both corroded. This is from coolant leaking into the chambers (because it was sitting for long periods of time and the seals just drying out over time) and the chrome becoming weak and flaking off. Notice that all of the corrosion happened at the bottom of the rotor housings.

 

We needed new housings, with that we went further and called up Atkins Rotary about their new cut down 13B GSL-SE housings. Excellent option for improved reliability and performance gains.

I called the customer and stated that it would be a shame to just put it together without adding in some needed porting. Based on his expectations, we did a mild street port on the primaries and larger on the secondaries. The goal is solid horsepower gains without sacrificing drivability. Big ports are not always the answer, it is all about flow. Our experience with altitude and street performance means we get it right.

Our engine build program has many years experience & knowledge, we build quality motors.