1988 Lancer, 5 speed, 4G15 engine. Blow by hose fills the aircleaner with oil.\r\nHave replaced PVC valve, measured & honed bore, replaced rings, vacumed checked valves, replaced valve stem seals. Please help!!!

You describe the situation as a heavy blowby. In the usually accepted meaning of the term blowby relating to an engine, means piston blowby and is recognised by a large amount of whitish vapour being expelled through the crankcase breather, dipstick tube and the oil filler cap if removed. This usually indicates the excessive wear of cylinder bores, pistons and piston rings that are no longer capable of sealing and allow combustion gas to blowby.

If the vapour puffs in sympathy with the engine speed it suggests stuck or broken piston rings confined to a single cylinder or a damaged piston.

It is difficult to understand how this would happen with a newly overhauled engine that surely must have been rebored and had new pistons fitted in order to qualify as overhauled. I can possibly advise you further if you post details of the overhaul in the comments section.

Not unrelated but perhaps surplus information just now - new cast iron piston rings take 500 miles to bed in to new properly honed bores while steel rings take 1000 miles. It is important to complete those miles with the engine filled with a base or low grade engine oil or proper running-in oil. Filling a newly overhauled engine with a modern high-spec oil can mean the piston rings will never bed in and forever afterwards the engine ios likely to smoke and consume a lot of oil.

we are USA
no KB here, not a one., sorry why ask Yankee's this./..??
your machine shop would not ask that question.
a real overhaul (if measurements prove the case, all parts are MIKED)
1: measure bores. top/bottom and 90 degrees.
2: then bore and hone it to next oversize.
3: then new pistons and rings. and all new bearings

any thing, less is a DIY, trash build.
shade tree , hack.
(the Bernard Lawrence Madoff" ) way. (dig?)
there is one more way, if measurements warrant. IT.
light hone,.
new rings, std, size or what's there, now.
then keep old pistons if lands measure ok. (inspections here are many )

I guess you don't have the micrometer sets to do this right?
inside bore gauge. etc.?
what we do is take the block to a real machine shop
the mic it for a fee. (some do it for free)
then they tell you what is best, and is always the best answer.
why not let a pro rebuild your engine.
for max future life, not lowest cost and shortest life.

ask how to clean a block after honing
its not easy and must NOT BE SKIPPED.

4th per inch diameter of bore is the norm for a water cooled engine .so your bore is roughly 3 inches from memory so a ring gap of 12 to 15 th ,check the thickness of the ring in the piston groove as well as up and down movement can and will cause excess oil consumption .give the bore a hone as well with a special honing tool ,not that expensive from a motor factor .

Most likely engine blow by or more precisely ring blow by. All engines have blow by, the PCV valve normally handles this but as the rings and bore ware the blow by increases.
Check that the PVC valve is operating correctly.

you did't state what engine it is. Some diesels have wet liners and others have dry liners. in both cases if the block was cracked you would have a water in the oil problem. I have come across this problem before and it basically comes down to mechanical experience. Rings will only go on pistons one way to work properly. If they are put on upside down they act as oil pumps and collect the oil from the bores and burn it in the chamber. Will empty a 5 gallon sump in 100 miles.
Next some mechanics prefer to save money and so do not replace the liners ( pistons ,rings and liners come as a kit) but rather hone out the bores. Two problems with that idea
the bores do not handle a hone well and so loose the hone marks quickly ( glazed bore = oil usage)
the angle of the hone marks is critical as they are there to trap oil for lubrication and turn the rings to prevent undue wear in the ring grooves. If the oil pistons were used with out new rings that are set to the right gap then the rebuild was a waste of time and money. Diesels are critical on measurements because of the high compressions that they run at and if the gap is at worn out gap the compression fire comes down past the rings and ignites the combustibles in the sump oil. The oil turns black very quickly , disappears or will not drain out when cold ( tar like substance)

blow by tubes are there to vent combustion pressure in the sump. This pressure is generated by combustion pressures escaping down past the rings. If there is a ring problem or a bore problem this gas blow by becomes excessive . When an engine is running the hone marks of the bore continually causes the rings to rotate and at times the ring gaps will line up and the compression gas goes straight to the sump ( sometimes noticeable blow by). Rings that turn this freely indicate wear and loss of ring tension. The method of diagnosis is to have an evaluation of the engine condition by a compression test.

old man the engine is old too. the rings do not seat well against the cylinder walls anymore, same with the valves. this creates "blow by", meaning crank case stuff is going through the PCV valve into the air cleaner. take a look at the inside of the valve and the PCV hose and you will find oil residue. time for a rebuild, it has more than done its job.

Blue smoke is usually an indication of bad rings, which allows engine oil to be burned as you drive. The fix requires engine teardown, pulling off the heads, removing the oil pan, and removing the crankshaft, rods, and pistons. The cylinders may need to be bored, but at the least they will need cleaned up with a hone. The old rings taken off and new rings istalled. If the engine needed bored, then new pistons must be installed. Then, put it all back together.

Hope this helps you

Your engine has an issue, on the cylinder with the wet spark plug, that is resulting in motor oil getting into the combustion chamber. The two main causes are a broken piston ring or worn valve guides/damaged valve guide seal. The former is a bigger issue as the pistons have to be removed to replace piston rings, which is a major undertaking and often reguires engine removal. The valve issue is significantly easier, which can be cured by what is called a "top overhaul". However, even a top overhaul is beyond the scope of a casual DIY pundit.