Finally got engine apart - now I have some questions about engine condition
 

First, some background: For those who don't know, my engine has been having problems for a while. I went to Germany for 5 weeks this summer, and when I came back it didn't run right. About the second time I drove it, it was flooded when I tried to start it up again. It continued to flood even if I used the fuel cut switch. I finally narrowed it down to clogged/leaking injectors. The place I sent them to flow-benched them and 2 of them failed the pre-test.
When I got them back in, it took a while to get it to start and when it did start it sounded like it was on one rotor. I did a compression check: 90-90-90 front, 30-0-0 rear. I thought something had fallen in the intake and popped a seal. Needless to say I wasn't happy as this rebuild only had about 25k on it.
I was in an apartment at the time and had no way of doing anything with the engine at the time, so I waited for a few months until I moved to a house. It was still another few months before I had the time to get the engine out, and I finally got it apart today. Here is what I found:
Basically, the front rotor looked fine. All the seals were in good shape and came right out. The rear rotor was a different story. All the seals were intact, they were just totally fused in place, I assume with carbon. Most of the seals were almost totally flush with the rotor and wouldn't budge. I managed to get one of the small pieces of the apex seal out, but broke the tool I had to get the seals out when I tried to extract the rest of it.
Also, the front rotor is relatively clean, while the rear is quite carboned up. There was also a large carbon deposit built up on the rear exhaust port.
So my question is this: What could cause this to happen? Running lean/rich? Bad spark? Bad compression?

Come on, no one has any ideas?

oil seal maybe???

Looks like you were burning alot of oil.

Yeah, that makes sense. I guess I'll go look at my oil rings. Anything in particular to look for?
Edit: just went a looked and I don't really see anything wrong with them just by looking at them. Any other reasons for this? Oil nozzle dumping too much in?

Could this also be due to running lean? My injectors were pretty damn bad, and it could have been leaning out.

For 25k miles, that engine is disgusting! :(


-Ted

what kinda of motor oil do you use and how frequently do you change your oil. since 7 are oil injected they tend to burn oil unless frequently changed.

Is that intermediate plate cracked!

almost looks rusted... i can't tell without touching it, though. is it possible there was a tiny coolant leak from a twisted/cut coolant seal or a defect in the irons?

I don't think the rotor itself is rusted, I think its just the picture. Now there did appear to be a bit of rust in the coolant passages, but thats normal, isn't it? Especially if it was sitting for a few months before I could drain the coolant. I never had to add coolant, either. I use Castrol GTX 20-50 and change it every 2500 miles, using a new OEM oil filter each time. Also, its not cracked, thats just road grime built up. Theres a ton of it in my engine and under the car. I'll try to get a picture of the rotors next to each other so you can see the difference. The front rotor is in pretty good shape.
Edit: You can see what my housings look like here: https://www.rx7club.com/showthread.p...6&page=2&pp=15
They are are in pretty good shape.

Carbon buildup can be due to running very rich, or burning oil, or both. Unless you had a flattened oil control ring (or a broken ring carrier) or poor porting, then I'd tend to rule out excess oil burning on a recent rebuild.

Well, theres pictures of my ports on the link I just posted. They are pretty large, but the same on both sides, so it shouldn't be due to the porting. I doubt it was running rich, as my injectors were pretty clogged. The oil rings looked to be intact, but I'll go check for a flattened oil control ring in a little bit. Any idea why that might happen? I'm guessing that oil got in the rear chamber while it was sitting and when I started it back up, it burned and caused the carbon lock. Could that happen? Also, is it possible that one of the oil injectors leaked oil in the rear while it was sitting?

Heres some pictures of the rotors. The stuff that kinda looks wet is oil that got on it after I took them out. The left one is the front and the right one is the rear. It may look like rust on the rear, but thats just the way it shows up on the picture. If you look at the pic of the exhaust port I posted in the first post, you can see all the carbon build up on the bottom of the port.
Also, what should I look for with a flattened oil control ring?

If the oil rings fell out of the rotors when you pulled them out of the block, they were flattened. Round o-rings are tight enough that they hold onto the rotors.

I'm thinking one or 2 of your bad injectors were on the rear, and were dripping fuel and causing it to be overly rich on the rear vs. the front. I've seen it before.

Well, all of the oil rings are still in the rotors. In fact, they seem to be in quite well. Also, they all passed the leak down test, they just had bad spray patterns and were clogged. I attatched a pic with the before and after flowbench results.
To elaborate on what happened, about 4 days after I got back from Germany, it started the flooding. I drove it around for another week or two because it was my only car, then I got my MX-3. It sat for 3 or 4 weeks until I had the time to get the injectors out and sent them off. When I got them back, it appeared to only be running on one rotor and I messed with it trying to figure out what the problem was. Then I finally did a compresion test and saw that the rear was 0-0-30. It then sat for several more months as I had no place to work on it.

Well, I dont know what more to tell you, except that it is what it is and you have to deal with what you've got.

I know, I'm just trying to figure out what caused it, for curiosity's sake, if for nothing else. Also, how do I get the seals out? I already broke my tool (dentist's scraper) trying to get the apex seals out. They don't seem to want to budge.

Let them soak a couple of days in a solvent tank or degreaser of some kind. I've had good success with purple power in a small tupperware tub just big enough for 2 rotors...you'll need 2 gallons to fill it up. Most of the time I use a tank full of mineral spirits for general light cleaning.

Take an old screwdriver and grind on the tip a bit so it is slightly smaller than the seal you want to remove, and drive it out from one end by tapping on the screwdriver held sideways with a hammer, being sure not to disturb the very SOFT rotor tip. Same for side seals. Corner seals, if they are stuck...remove the rubber plug with a pick, then use a wide blade screwdriver to twist the seal, then come in from behind from the apex slot with the screwdriver and tap it out.

Alrighty, thanks. Where to you get purple power? Hardware store?

autozone.

I wouldnt leave the rotors in there more than 2 or 3 days...I've seen the stuff eat up the coating on the bearings when left for a while, especially at full strength before it is diluted a bit with dirt and oil after a few sets of rotors.

If you plan to keep the corner seals, be very careful when pulling them.
They are fragile.

My favorite solvent is brake cleaner.

I'm not planning on keeping any of the seals. Also, I just registered that none of the corner seals had plugs in them.

plugs aren't needed, they help with assembly though.

The plugs are useless, they harden within 10k miles. Their aim was to keep carbon out from under the apex seals, and they fail in that aspect. I havent installed a set of plugs in an engine since 2001. Compression is unaffected without them.