Posted by NCWayne on December 22, 2016 at 15:54:51 from (173.188.169.54):
I've been building engines, or all types, for more than 20 years, and have run up on a problem I can't figure out, nor can anyone of the multitude of people I know (many of whom have build engines longer than I have) can figure out either.
I had a N844T Shibaura brought to me that was pumping raw oil out the exhaust, after supposedly being rebuilt. My first thought was the turbo. It had some wear, and I could tell it had never been off, so I had it rebuilt. The problem seemed to get worse.
So I opened the engine up. I saw nothing that jumped out at me that would cause the problem, other than that the supposed 'rebuilder' had lied to the owner, and had not rebuilt the engine as he said he did. This was apparent in the old pistons, worn bearings, etc.
So, everything went to the engine machine shop, and came back to me with a refreshed head (valves and guides seated, but not replaced as they were within wear specs), bores still within standard spec, but honed and crosshatched, etc, etc. In other words, it was done right.
Built the engine using all new parts. Test ran, and it began spitting raw oil out the exhaust again. Given that the internals were new, I had the turbo rebuilder check it again. They found nothing wrong. I then set up and ran the engine without the turbo, and it was still spitting oil out the exhaust on #2 and #4. The oil appeared to be coming from around the valve stems.
So, checked compression, and it was good all around being in excess of 410 psi just by turning it with the starter. So I pulled the head. No indication of oil being burned on top of the pistons, and only a small dark spot where the injector fires on each one.
Pulled the valves, and as the shop had told me they were worn, but still less than half of spec toward the limit. Took the head back and had it completely done. They had to machine it to put in replaceable guides (which it didn't origionally have), but it came back to me this time all new.
Got the engine together last night far enough to do another compression check. Again I got 410 -420 on all 4 cylinders. I finished it up this morning and test ran it. Within a couple of minutes, it was slobbering oil out of the exhaust again.
This time when I pulled the manifold, not only were #2 and #4 wet, but #1 was wet, and #3 was getting there. Funny thing though, on #1 and #2 valve stems were soaked in oil, #3 had some on it, but not as much, and #4 was dry as a bone.
Now I'm at the point of looking for any ideas of what could be happening as I have covered everything I can think of along with everything anyone I have been able to find has thrown out to me.
If there was ring wear, or the rings weren't seating, I could understand blowby causing oil to get pushed into the cylinder on an intake stroke, but there is no indication of blowby, and with 410 plus pounds of compression, it's obvious the rings have seated. Nor do I see any indication of it being an oil control ring issue. If that was the case, why was #1 dry as a bone when I pulled the head the first time, but the second time now, it's wet after having the head completely worked, and the pistons not having been removed?
Like I said, I've covered all scenerios me, and about a dozen others have thought of, and eliminated all of them by testing. Mind you I have done far more than I've stated, but getting further into details on what all has been done would take three times this amount of writing.
That said, do any of you guys have any ideas, because I and many others I know, are out of them on this problem?????????????
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