Forums are meant to help each other, don't be sorry as I am glad you posted here!
Please send photos or detailed descriptions of what you find, it is of great help to find out where the problem is... Were these 2.3L engines? I bet the majority of people who owned these cars while they were fresh just didn't change oil on time, hence the build up.
I will let you know if I can find anything on the piston ring spec.
Thanks for the feed back Big Dill. I actually found the (or i should say "a") spec on the ring end gap. Unfortunately it's in a Haynes manual. These are good books, but I prefer OEM service manual stuff. Or even actual machine shop info that describes how to calculate the gap yourself. Since this is my son's DD, I just want it as stock as I can get it.
And "no", not 2.3s. These engines were both 2.0s. I think it's the L4 family. And I'm not sure who the actual designer is. I did know, but can't recall if it's Ford or Mazda. It is however referred to as a Duratec 2.0 in some places and has the FoMoCo brand in the block casting.
I certainly will post some pictures once I get this one back together. Currently: I'm taking way too many pictures of the build process. I did quite a bit of work on the heads as a trial run for future projects, and learned a lot. That's another thread.
As for the oil issues at hand; It's hard to say what the root cause is. It could be a design issue; but that doesn't explain why some have had great performance with regular oil changes.
IMHO: I think more than likely it's a combination of issues.
it could be the brand of oil (cheap and non-synth);
it could be the use of non-synthetic oil coupled with long OCIs (If the engine was "actually" designed for synthetic use only);
it could be that the PCV needs to be changed out more regularly.
my favorite thought is that the VCUs get hacked and mucked around with. While I was reading threads on one of the other forums, someone said that running the mixture on the wet side is always better if your looking for more power. I think it went something like 'the wetter the better'. Which is far from the truth.
The mixture has to be at least very close to what it was designed for. Unless you're pulling it out once a year to clean it up and replace the rings and check the valves. If you run it too lean, it runs hot and dies sooner. I'm not really sure what all could happen... warped head, burnt valves..
If you run it rich there are other issues. Carbon building up and the cylinder walls get to looking like cylindrical mirrors. Not to mention the clogged piston rings and pitting on the valve lands. This (I think) could lead to higher than usual blow by; pressurizing the crankcase and causing more oil vapor to get recirculated back through the intake through the PCV.
In my case, I really think it has more to do with someone mucking around with the VCU code and changing the mixture. I say this because essentially, this will be the third engine for this car (well. the third one didn't actually come out of this car). But it's my story and I'm stinking to it.
So, both of the ones that I pulled apart where full of carbon. I need to take a better look at the one that came with the car. And, yes, I'll post pictures. It will just take some time since that one is buried right now. And I wasn't thinking about documenting anything when I started all this.
To answer Datsun's question: The engine that came with the car: I have no idea how many miles were on it. It had all the markings of a junk yard engine when he brought the car home. That's about the time I started trying to think positive. Then: It ran ok until it didn't. Used a lot of oil in the meantime, but my fingers were crossed. (note to self: that doesn't work. Needless to say; the positive thinking also did nothing)
The engine that we got to replace it came from a junk yard in PA. the internet said 11k miles. I first found one in Florida for about $1700. It supposedly had either 28K or 60k miles (Can't remember). That's when I found the one in PA. That one was $900 and came with free shipping. Plus they knocked another, I think, $50 or so off for something, not really important since the engine showed up with a smashed oil pan and a broken valve cover. In addition, the packing slip said 110k miles. They forgot to include the one zero on the internet.
For now, I'm going to try to attach a picture to see how it works. It's just a teaser if it works. But if it doesn't: it's just some pieces of a piston....
no cliff hangers here...