PCV Catch Can

[Tomcio]

Let me chime in on this subject...
Intake vacuum draws air through the air filter and that black hose going to the oil filler cap. In effect there should be a little bit of vacuum in the crankcase unless there are holes to the outside allowing air to enter. Another source of too much air (or gas) in the crankcase is the ring blow-by.
In the first case (a hole allowing air to enter the crankcase) you would probably see oil leaking in that area. This includes valve cover seals, timing chain cover seals or any other oil passage with no positive oil pressure. A leaking oil pressure sender will not allow air to enter the crankcase. If you do not see any oil on the outside of the engine in those areas but there is a lot of oil in the intake I would check cylinder compression. That might indicate excessive piston ring blow-by which creates too much positive pressure in the crankcase pushing too much oil into the intake manifold. A dry compression test first, then again after adding a bit of oil into each cylinder. I would expect to see a jump in compression indicating worn rings. A cylinder leak-down test might also be useful here.
In many cases this is a good indication of a worn engine.
A catch can is useful on turbo engines because a turbo creates higher cylinder pressures and higher ring blow-by in effect pushing the oil out of the engine.

In a well maintained naturally aspirated engine there is no need for a catch can. If you need one, you need to address the issue causing the excessive crankcase pressure first. Adding a can will not fix the problem... it's like putting a band aid on a broken arm.

[Dutch]

Hi Tomcio, I concur with what your saying. Because I'm doing a complete rebuild I can see what's going on in the engine. As I mentioned I did the teardown for a reason, bad performance, leaking etc. I'm expecting a clean and lean engine after completion without leaks of any kind (oil , vacuum).

I started the topic to see if anyone had tried it and or had the same issues I had. Thanks for your insight.


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[Tomcio]

No problem, glad I could help
If you're doing a full rebuild (guessing from the picture in the original post it is a COMPLETE job) then you don't have to worry about a catch can. If the rebuilt is done correctly the can will just stay empty. There are some gasses from the blow-by that cause some yellowy-brown film on the intake but that is mostly gas and some very fine mist. All that should be burned inside the cylinders. Save some money by not buying the catch can

BTW, it's so nice to see people from all those familiar places... Tampa and Pinellas county. I used to live in Clearwater.

Good luck with the rebuild! You can use my car as a benchmark because from what I can see I'm lucky to have one of the best PRVs out there. My car (before I started a ground up restoration) was running 0-60 in 8.0 seconds pretty much every time. With the mods that you have and a freshly rebuilt engine you should easily beat that.
My engine is 100% stock, manual transmission.

Tom

[Delorean Industries]

We have proven through extensive dyno testing that the factory crank case ventilation system does not properly function at sub 100 kpa levels let alone under boost. This is why every island/bae car in existence pushes seals at sub 130kpa. At the very least venting is required in both valve covers independently of each other with basic breathers on naturally aspirated applications. On forced induction applications a secondary scavenging system is required with a one way recirculation valved return line into the lower case. (valve orientation allows for scavenging pump to pull oil back into case but is over come and closes if crank case pressure exceeds scavenging pump cfm.)