Mazda SA Rx7 Engine rebuild process & details
1979 Mazda Rx7 | This car is a local car bought new in Denver in 1978 by its current owner. Engine failed several years ago, here is the page where we will share our removal, build process and installation.
Mazda Rx7 Gallery for 1979 rebuild in 2025
Our builds are solid, take more time than usual with our ultrasonic cleaning, careful measurement / inspection. We build good motors
June 2025: Here we drain the fluids, start marking hoses and wires and start the process. The exhaust was too corroded for us to remove the bolts, a new stainless steel (higher flow) will be added later. This car had a major oil leak and with the motor, the transmission will be removed and ultrasonic cleaned. A dirty transmission will run higher temps than a clean one. Do it right.
June 2025: Engine gets the main through bolts removed (they came out hard, needing more than 80 ft/lbs to loosen. This is not a good sign, this means the engine ran hot), rotors get some fresh air, the rear rotor looks good, no broken seals and minimal wear.
The front rotor is very corroded, looks like water got in here, rusty and all seals stuck hard. Ultrasonic got them clean, we shall see if we can get the seals out, my hunch is we will need to source another 12A rotor. The rotor housings are torn up on the sides, meaning the apex seals ran hot, bowed and wore out the housings. More pics to come.
July 2025: Rotors came out clean with the ultrasonic, took some time to get the side seals out, see pic of small piece stuck. One has to be very careful that the groove isn't damaged, the heat of the ultrasonic helps. Sometimes you can save these, in this case we got it.
All the side plates look good, going to need to be sanded flat and of course remove the gasket and other material built up, Just ordered new seals, gaskets, o-rings, need to order rotor housings next and then we are off to the build.
July 2025: Pressure washed the engine compartment, lots of oil / grease / dirt from having oil cooler leaking. Transmission ready for the ultrasonic cleaner inside and out.
As you can see, the pressure washer got some of the gunk off, next is the magic of the ultrasonic to get it really clean.
July 2025: With the ultrasonic warmed up to 135 degrees, time to lower the transmission into the unit. With the fill / drain plugs removed and tailshaft open, several 10 minute sessions and its ready for flushing and to be put back together. We flush it with water and brake kleen and put transmission fluid back in it right away, rotate it to coat all the parts and drain. New throwout bearing and its ready when the motor is built. She is clean inside and out.
July 2025:
Replacement of main / rotor bearings. We use the Rx8 bearings due to their improve flow characteristics. The small scuffs are due to the fitting of the pressed in bearings to the eccentric shaft, these will be polished out. On street motors, we like a tighter fit than for a full race motor.
Next, we have the oil control rings all installed, the grooves all cleaned and prepped, next we grind the side seals. This is a time consuming process to make sure we have consistent combustion pressures.
The side seals have all been cut to tight tolerances, this is a NA motor so we can get them better than stock and still have room for expansion. I like .0025-.0030 to corner seals. We polish the ends to match the curve of the corner seals. The wood plates are cnc'd to hold the rotors in place and keep everything safe until we put the motor together. Details matter.
These pages will be updated as we get deeper into the teardown, cleaning, measuring and reassembly. Stay tuned
Every engine build deserves the time and care to understand why it failed and what needs replacing
If you have a question please check out our contact channels
Frequently Asked Questions
Question #1 How much will my rebuild cost?
Every rebuild comes down to what your motor actually needs. Anyone throwing out pricing at this point is going to be wrong. We don't replace anything that doesn't need to be replaced. We do replace seals, gaskets, springs, o-rings. Most engines need new rotor housings as they usually get torn up from overheating, poor cooling and abuse. Get it right. know your budget and expectations.
Question #2 What if I want performance upgrades?
Performance upgrades, especially at our climate need experience, knowledge and the realities of our high altitude and hot climate. We have that level of experience from our racing in Colorado. Just ask.
Question #3 How long do rebuilds take?
Rebuilds take time, the real answer is what we work together to accomplish, additional time is needed if we need to send parts off to be machined. Our porting and side seal clearances are done here in house. We will be upfront with every project to let you know and keep you informed along the way with photos and information.