I replaced the cylinder heads on my 1993 ford Ranger 4.0l. The heads are new castings. After initial start up the engine seems to idle a little ruff has a high idle 1500 rpm. After the engine idles around 5 to 10 minutes the PCV valve blows oil out around the PVC valve seal on the valve cover. I also replaced the PCV valve this morning thinking it was causing the issue. The excessive pressure blowing past the PVC gasket sounds like a blow off valve on a turbo. This was not happening before the heads were replaced any help would be appreciated.

 

Check the Breather hose, it runs from oil filler tube to the Fresh Air Plenum, its there to deal with excess Blow-by as an engine gets older

Blow-by occurs on all piston engines, its the exhaust gases that "blow by" the the piston and rings every time a cylinder fires, as an engine ages more gases "blow by"
The gases are VERY hot, so vaporize some of the oil coating the piston and cylinder walls, this is where ALL the oil vapor in the engine comes from, nothing else in the engine is hot enough to vaporize oil

The PCV system was added to prevent these exhaust gases and oil vapor from polluting the air, so they are sucked into the intake to be burned, again, and then treated by Cat converter
There should be slight negative pressure at all times, when engine is running, in the crankcase and valve covers
The breather hose is there to allow FILTERED AIR to be pulled in so too much negative pressure doesn't occur and as an "overflow" if to much positive pressure occurs

And you do not have an EGR system correct?
In 1993 I think that was Calif. only.

 

There is no EGR. I inspected the hose going from the passenger side valve cover to the intake tube. The hose looks fine no splits or cracks are visible. Could this be caused if the lower intake is leaking?

 

Why were heads replaced ?

I'd check the compression of the cylinders now to eliminate rings.

 

I did the head gaskets 5 or 6 years ago because of a bad head gasket. I noticed a small crack between the valve seats. I Didn’t have the funds for New heads at the time. The truck was running fine after the first head gasket replacement. Fast forward to January 2020. I was going ice fishing and lost the fan belt. The truck overheated I limped the truck to the nearest town ( driving until the truck got hot and pulling over to let the engine cool down)replaced the belt and fill the antifreeze. Had the money So I figured it was time for new heads.

 

If you have or can get a vacuum gauge(good tool to have, under $25), you can test intake vacuum, 18-21" is expected at sea level, -1" per 1,000ft above sea level, because I see you are in Utah so you are above sea level a bit

Good testing article here: https://www.gregsengine.com/using-a-vacuum-gauge.html

You should test after engine is warmed up for 5 minutes or so

It tells you if compression might be low

 

I checked the vacuum it is 15 in Hg. I’m at 4,226 elevation.

 

So rings are fine, worn but fine, 15" at 4,000ft would be 19" at sea level, not 21" but still just fine
Was it steady, or was there a misfire showing?

The excess blow-by can be from head gasket issue or cracked block..............keep a good thought, lol

Pull off the breather hose at the air plenum end, start engine
Smell the fumes coming out, raw gasoline smell, would be gasket or block issue