As an engine builder, taking the engine apart is one of the most overlooked actions. How the engine comes apart will tell you a lot about the engine and how it was driven.
- How brittle are the components that sit on top of the engine? wiring harness clips, connectors, oil injection lines?
- How do the gaskets look all the way from air-box to the intake ports?
- Just taking note of how tight the bolts are will provide an understanding of the number of (more than average in temperature) heat cycles there were. This gets overlooked a lot.
- Ignore these items and it comes back to bite, replace everything and you are doing your customer a dis-service.
A good example is how a motor that came out of an autocross / track day car vs. a daily driver with occasional spirited driving (hitting redline) is going to be different in how it comes apart.
Another good indicator is what shape the oil injector lines are. Because they are made of plastic tubing and they transfer hot oil through them, checking them for brittleness and if they still flow oil helps.
A caked up oil line that doesn't flow means to make sure to compare rotor housings. Reality is that these types of indicators will help in diagnosing why the engine failed and to replace components to make sure that it doesn't happen again. Most Rx8 rotor housings are going to need to be replaced.
There are a lot of wires, lines and hoses that hide underneath the intake manifold and they take a beating with the heat cycles / temperatures.
The key here is to identify those parts that are at the end of their useful life. This is the difference of where a motor that is rebuild and put into the car starts up properly the first time or not.
Connectors are the first thing to fail on many first series Rx8's as they are older and especially if this isn't the first time the engine has been pulled. Water temp sensor, fuel injector connectors are the most common.
- Then, we get into the engine.
The main long tension bolts that hold this sandwich together are going to tell how hot this motor got. The factory specs the Rx8 bolts to be +- 28 ft/lbs. each. On motors that have seen high temps / heat cycles these bolts will come out hard. When I can feel the yield in the bolts (twisting / fatigue), I know that the rotor housings are junk in terms of expansion / overheating.
After that, pulling the plates / housings off is next. Grabbing all the pieces (apex seals, side seals and corner seals) the next factor is the oil control rings. When they fall out of the rotors, another sign of running high oil temps over long periods.
After the motor components are lined up on the bench, time to measure up everything and take notes. This is not a 5 minute job, this is where the details make all the difference in a quality build.
Next we move all components to the ultrasonic cleaner. This is where getting everything cleaned properly is mandatory. Heat, soap and ultrasonic cleaning is second to none for these motors. Breaking up carbon build up, grease, oil and dirt, this process is the best way to get it right.
Expect solid results from your rebuild, quality matters.