Fasto's Rebuild
 

Well it appears to have finally caught up with my ride. Low compression... No symptoms until just outside of the extended warranty. Not too surprisingly MNAO was unsympathetic. The timing was a bit disappointing as I'm working the rebuild of an old car and was hoping to finish that before problems set in with the RX.

Symptoms:
After a cold weather road trip I lost some coolant, but it never happened again. It began starting slow (hot and cold), but never refused to start. After installing a starter for a '07 (305 RPM!), it had no problems at all. It was perfectly drivable, but it wasn't the same car as it used to be. I could tell it was losing power in the low RPMs, and I was getting a bit rough on the clutch to compensate. I certainly could have kept driving it as it was, but it seemed like a good time to get a rebuild going so I seized it. As soon as I pulled it, my work schedule got crazy, but that's how it goes, right?

I can't find my compression test numbers, but if I remember right all six were around 87psi at 305 rpm, so pretty bad when corrected. I'll post them when that sheet turns back up.

Photos from the tear down:
RENESIS Eval Photos by fasto659 | Photobucket

Condition of specific components:
I'm keeping all of the leftover parts for awhile for additional examination by request.

Apex Seals: I'm assuming that the height spec ranges from new, to completely worn. If that's the case they were ~80% worn. However, I didn't find the rebuild manual clear as to what range the tolerances were indicating. No arching or uneven wear that I could measure.

Side Seals: Surprising amount of clearance to the corners, and plenty of carbon down in the springs.

Exhaust ports: All had the tapered opening clogged by carbon, which was really stuck on there. This may be due to the decarb processes that I tried pre-rebuild.

Housings: Chrome flake was evident on the edges of the expansion region on both as well as ridges worn following the edges of the trailing spark plug (Over torqued the plugs? Bad cooling?). One had significant chrome flake on an oil injector port, possibly due a decarb attempt through those injectors. It may be a coincidence, but in general decarbonization seems like it should be done carefully and often to prevent clogging, or more likely only as a desperation move. I don't care for the method of using the oil injectors as they have enough of their own problems as it is.

Stationary Gear Bearings:
Standard scuffing of chrome, not convinced it's a huge deal, but switching oil anyway.

Rebuild photos:
RENESIS Rebuild Photos by fasto659 | Photobucket

Rebuild components:
I debated these a lot. I even thought of the ceramic apex seals, which I still find an interesting choice. However, in the end, I stuck with almost exclusively stock RENESIS parts. I think I ended up with Atkins oil ring seals (viton), but don't believe an upgrade was needed.

Parts replaced:
Apex, Side, and Corner seals and related springs
Both rotor housings
Stationary Gear bearings
Oil injectors (all four originals were shot...)

Kept:
Oil rings, gas control rings and related springs
Rotors, Rotor Bearings, End Plates
MOP and lines, though thoroughly cleaned

Upgrades:
Hand Cut Side Seals
Mazmart Water Pump
Mazmart Oil Pressure Mod
SOHN Adaptor w/ Idemitsu 2-Stroke, plus 6oz per tank premix
Rotella T6 5w40 Oil going forward (5w20 for break in as I had some to use up)
Atkins Thermal Pellet Bypass
Polished the ports, as they were much rougher cast than I expected. (no porting)

Engine Stand:
A lot of people commented that a adapter plate would be required for an engine stand. I found one big bolt hole lined up great as-is. Flipping some of the arms and putting some bolts with spacers into the A/C holes (with bushings as those bolts are rather narrow) was enough to get by.

Experiences post rebuild:
Cleared the computer NVRAM, disconnected the catalytic converter and it fired right up and let out the bulk of the Vaseline in smoke. However, we had to shut her down due to a fuel injector leak. That took awhile to figure out, and it turned out that one of the tabs on the fuel rail was bent. I took a chance and bent it back. It seems to be working...

After that I was trouble shooting a small amount of smoke from the engine bay after it got warm. Not sure what it was exactly, and it went away on it's own. I probably put a greasy hand on the cat or exhaust manifold and it just needed to burn off.

Only other issue is one that has been brought up before. Under light throttle, there appears to be a slight ringing or whistling noise. It may have been there before, but it's hard to quantify the level of paranoia that comes from a project of this magnitude.

Otherwise, it's been perfect. No leaks, runs stronger than I ever remember, and idles solid as a rock. It feels new, and my friends can't believe how well the car drives. I have not retested compression, as I'm not convinced it matters. Oil analysis of second change (500 to 1050, forgot to send in the first 500), showed only a slightly high silicon content, probably due to all of the RTV.

I realize that posting this may encourage others to do their own, and it seems that current opinion leans towards discouraging that. Let me clarify my skill level and try to sum up my experience, so that you may decide for yourself. I'm an engineer who is bound and determined to fix everything himself. I'm nearing completion on a body off restoration of a '68 Triumph TR250. I've found that project to be massively time consuming, but not too hard (other than the body work...). With that being said, this is a different experience than an old car. Sensors, wires, and tubes everywhere, which is more work to hook back up, but refreshingly easier to start back up (no tuning required!!!). I believe it's an easy engine to rebuild, but as usual the devil is in the details. Differing opinions on issues like side seal clearances, along with confusion about how our engine is different from previous 13B's leave lingering doubts. The hardest thing for me was overcoming the paranoia that I did something wrong. YMMV.

I'd like to publicly thank the forum as a whole, as so few cars have this active of a community. Specifically, though, a handful of names deserve mention: RotaryResurrection, Ash8, RotaryGod, TeamRX8, and Charles R. Hill. The RX7 sites were very useful too. AaronCake deserves mention there at a minimum.

Looks Great!!!

And if the noise your speaking of is a light kind of whining whistling noise under very light throttle I believe its normal as mine makes a noise like that.

Curious if you had the irons lapped? If so, by whom?

Coldwound,
Yeah, just like you said it. Seems like other people think it's normal too. I just I'm just noticing it now because I'm hyper-aware.

Smutterbutter,
No, I didn't have the irons lapped. While I didn't have the perfect setup to measure it, my dial gauge showed no real step wear. I'm also a bit nervous about removing too much nitride, despite vendor promises. I guess if I would have I would have looked further into Racing Beat.

Charles,
No problem. Your rebuild vid (mysql's?) spurred me to do it myself.

Both good questions: 90175 on the ticker, probably 90% city miles. REVi + ram on the intake, no engine mods otherwise. 5w20 motorcraft for the all but maybe one oil change.

Well done, glad you successfully rebuilt on your own!

Shady,
Thanks man.

Charles,
Okay. I'll watch the pump. Still original so I'm probably coming due.

Not to start another oil fight, but wouldn't 5w40 be even better than Xw30 in both cases?

Posted From RX8Club.com Android App

very inspiring!!!

Thank you so much Festo!!!!!!!!!!!!!!!!!!!!!!!!

OH NO YOU DIDN'T SAY THAT CHARLES ...

the "MAZDA KNOWS BEST YOU KNOW NOTHING USE 5w20 FTW!" nazis gonna go after you ... :Eyecrazy: