Yes, quite a lot of oil mist escapes via breathers in all engines, which is one of the reasons that designs with catch cans have an attraction but may be difficult to make work. The plenum in the series 3 fuel injection intake is a low point in the intake and easily collects half a pint of oil. Fortunately, it doesn't upset the engine running too much.

 

This was the original filter location. The air flow at was definitely pressurizing the crank case. All of the engines I've owned had a vacuum line attached to the intake with an inline check valve.

 

I had a piece of scrap copper tubing and it allowed for a quick fix to see if crank case pressure was causing the rear main to leak. There is a long list of issues I still need to address to refine the installation of the Jaguar engine.

 

Apart from any effect of the air flow, you definitely don't want the filter. Flow from the breather is out from the crankcase. The filter serves only to block increase pressure in the crankcase as it oils up.

If you're not going to a more sophisticated system with a PCV (one way valves, catch can, etc), the ideal is to have the breather exit at or a little below atmospheric. Then, there's no pressure pushing oil out through crankshaft seals and the like, and not too much flow through the breather carrying out oil mist.
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A vacuum based PCV might not a good idea, the rear main has no seal. Creating a vacuum could cause air flow to enter the rear main scroll, possibly allowing contaminates to enter the engine.

 

to do it right, it looks like i'll need to route it back to one of the two new air cleaners i've installed. i think a plastic tube and fixing hardware for the tube was provided with each air cleaner. a hose of proper ID and two hose clamps should do it. if stout enough the hose may not need support...could i be so lucky?

 

Cut bottom of breather pipe at 45 deg. with long side forward, to create slight low pressure area at breather exit (I would not add the filter). With the exit below the engine you will have sufficient airflow. The length of the breather pipe is sufficiently long that you will have to trim it to fit.

Later "smog" cars vented breather to the back of the air cleaner(s) to burn blow-by fumes, unfortunately this introduced blow by oil into the intake system and made a mess in the carbs. I added a $25 eBay universal oil catch can before filters on my XKE. This is pure environmental, no benefit to engine or performance. I assume since you now understand it's a jaguar engine, you have the obligatory "oil drip pan" on you garage floor.

 

With a proper Plenum Chamber the oil drips out of the plenum chamber drains.

 

With your vehicle you can do as you like.

 

I just completed the first oil change. The oil filter paper pleats inspection was good, it was very clean with minimal contaminates on the paper pleats. This engine has the downward facing oil filter, you must allow the oil to flow back into the pan to get an accurate level check. With 6 1/2 quarts the oil level is in the middle of the Full area.

 

This was my first engine rebuild, it was worth the effort. The engine is running great and I got to experience the rebuild process.
The Moss 4 speed with overdrive was also an interesting project. It had to be disassembled, cleaned and inspected, then reassembled. There were some issues but they were easily resolved.