Oil catch can removal

[Payco]

Guys I had an oil catch can fitted when I had my engine work done but I have decided I would like to remove it  it for a cleaner look and less pipe work. The hose to the rocker cover I understand gets replaced by the cone filter I have ordered but the catch can hose to the side exit pipe on the engine block is my question. Do I need to block this off with a Bung ?. 

Martin

[paradime]

Is your engine turbo or an L series? Forced induction engines often have blow by past the cylinders that over pressurizes the case and gets vented off through a pressure valve. The catch can recaptures oil that's released in a fine mist. There is no need for a bung, in fact you want the pressure to be released. I removed the can in my SR20DET and have the hose venting to the ground.

[Payco]

Thankyou . No turbo, just stick L18 with 40 Weber DCOE carbs. So can I just remove the bottom hose from the block and leave it open ?.

[datzenmike]

Normally the valve cover hose went to the air filter so that under certain conditions flow would be reversed and any fumes would be sucked into the carburetor(s). The block vent pipe went to the PCV valve in the intake which provided a vacuum source to draw fresh air through the crank case.  None of that is happening here. Before the PCV valve the block vent pipe went down beside the engine where vehicle speed moved air past the tube causing a very week vacuum to draw fumes out into the environment. They were known as draft tubes. This is your best option.

 

The PCV valve draws filtered air through the crank case removing oil, gas and water vapors that will condense and dilute your engine oil much extending your oil change interval and the life of your engine. A 1950s engine might last 100k miles.

 

Here is a 1950's highway. Draft tubes were the cause of that black oil stain in the middle of each highway lane.

 

[Payco]

Thanks again Mike 

[datzenmike]

I don't think your catch can even do anything as it is connected.

[mojojojo78]

19 hours ago, datzenmike said:

I don't think your catch can even do anything as it is connected.

I was thinking the same thing. Shouldn't the hose from the block go into the catch can, then the hose from the catch can connected to the PCV on the intake? The pipe on the valve cover would then just have a small filter at least.

[yenpit]

You want a small filter on both........do NOT leave open & I would not suggest sealing up either one.  If your engine is healthy, you should be fine with filters, to keep dirt etc out.  If you see one or both filters getting oiled up and/or dripping, that means you likely have some blow by with the rings (some wear) & you will need to reconsider the use of a catch can 😎

 

We just got a customers 240Z in with a freshly rebuilt engine.  The builder did NOT seal off these open tubes, did NOT seal off or install an oil filter.  The car then went to body & paint, so there is at the very least, bondo dust & paint polishing compound everywhere.  We told the owner about it, but it is a moot point now...........we will simply clean what we can & fingers crossed nothing "heavy" entered any of those open tubes or oil filter galley!! 😫 

[datzenmike]

The engine will be slightly positive pressure and definitely not vacuum. Anything in the engine will be trying to get out. Dirt would have to fall in the L20B block vent to get in. Even harder on the L16/18 mounted horizontally on the side. There is still the screen in the block. As to the valve cover vent it is also baffled. Then there is the oil filter that catches every thing anyway.

 

Just having these two entrances open, filtered or not, is not ever going to do anything except vent to ambient air pressure. Every time you shut off the engine it will cool down and all the water vapor (gas and oil fumes too) will condense into the oil. Oil changes probably should be half what a PCV valve equipped one should be.... every 3k is about right for a '50s engine.  

[wayno]

I had the same thought about that catch can(how can that work), but we cannot see enough to say for sure how that one works, it appears to have a clear tube on the side that would let the owner know how much oil is in it, what else can we not see?

 

I thought maybe the intake could be modified to make a PVC work like I think Crash did, but that would require drilling and threading the 4 intake tubes/runners unless each side(2 runners) are connected together somehow as then it would only need 2 holes drilled and threaded.

[Payco]

Thanks for all your replies. I have removed it now but it was connected correctly according to all the photos online I have seen of Datsun 510 catch can connectivity.