Bit of an update, but more to come tomorrow when I pull it apart further.
I am suspecting based on everything so far, and what I'm about to talk about, that whoever 'rebuilt' the motor last time did it very much dodgy, or maybe inexperienced is the right word? I think cheaply fits. Don't get me wrong, I'm about as inexperienced as you can get in terms of rebuilding an engine, having never done it before, but I understand what needs to be done during the process, and I'm learning from other people as well.
Basically, it looks like the last rebuild was just done with a cheap rebuild kit, they didn't grind the crank, used non-oversized everything, and just put it back together (also don't seem to have touched the gudgeon pins). Doesn't seem like they've taken it to a shop for anything, except possibly a light cylinder hone, but with the looks of that scoring I'm starting to doubt that too.
On to what I've done since the last post in-between work:
I took the sump off, which was a mission because the gasket was seriously glued on there with gasket goo, and now I can at least see the bottom end:
Nothing obviously wrong, so I take the oil pump off, and start having a poke around, the big end bearings do have some side-side play in them, but as far as I'm aware there's nothing that you can do about that since it's the conrod itself that needs to be bigger to take the movement out.
All of the oil squirters under the pistons are intact, none snapped off which is perfect. I wonder if there's a better direction that these could be modified to spray, that better cools the piston?
Anyway, I'll trust Mr Nissan for now:
Great news too, the end caps have already been marked, so one less thing I need to worry about:
I got called into work so Dad ended up being the first one to take a big end bearing off, and uhh:
Yeah, pretty decently worn that one. And it looks like it's possibly had dirt trapped under it at one stage? It's weird, it doesn't have the brass bottom layer I'm used to seeing in pictures, so I'm not sure what to make of the wear marks. The crank does have wear lines in it, but I can't feel any lip with my fingernail so I'm not sure. There's a good chance the crank didn't get ground back to flat and round during the last rebuild, or if it did they didn't match it with oversized bearings, which along with general wear, would definitely help explain my generally low oil pressure
My summary of their rebuild:
Based on how much gudgeon pin movement there is, I'd say they took the sump off, slapped some new bearings in the bottom, without removing the crank, lightly rubbed the cylinder walls with a hone, put a new head on, and hopefully did some other top end stuff, we'll see though.
I haven't pulled a piston out yet, that''s tomorrows job, so we'll see how the rings look, because just like the bearings, there's a good chance they didn't match the rebuild with oversized parts. That would explain this, what Dad's assuming ring gap mark, and the blowby the engine has always had (where the ute has significantly less):
I went and talked to an engine builder in Caloundra on Wednesday, to get a general gist of what he thought should be done to the engine, and pricing, and it turns out he's a really nice bloke, who actually knows and has past experience with this engine, which is just awesome.
He's aware of the liner protrusion requirements in case it comes to getting new liners, he's actually the one who told me about all the oversized stuff to suit crank grinding and bore honing as well, and reminded me that worn bearings can cause lower oil pressure.
Once I get it down to a bare block, and can get all the bits to him in pieces, we'll have a look over them so he can tell me what he recommends with the bores, crank, pistons etc. Hopefully he should be able to source the new parts we need as well, oversized and all.
For those of you who just want to get back to watching landline
Bottom end is pretty loose, worn, and looks like it was cheaply rebuilt. Will be like new when I'm done with it.