Engine breathers

johnymd

johnymd

Club Member
I've been looking at what to do with regard to these 2 breathers. If the L-series is of a similar design to other engines then I would assume the rocker cover breather is an inlet and the one on the side of the block is the outlet. Modern engines use this air flow method to assist in returning oil from the head back to the sump which sounds like the right thing to do. So is the answer just to put a small filter on the rocker cover and feed the lower vent to the intake system? at the intake balance tube? I've pulled the carbs and all the hoses off my latest 240z and want to simplify what I put back on but do it right/better. I remember some time ago there was a thread about the benefits of forced crankcase evacuation and this is what I'm trying to do.
 
If the 'Cam Cover' breather is an inlet why is it connected to the air intake?
 
so filtered air is drawn into the engine
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I never would of thought of that Jon.

Rob - That's why I said "if" the L series is the same as other engines.

You see lots of people using oil catch tanks, which I'm not a lover of, and I'm sure they are not the best thing for an engine unless someone has fitted it with regard to engine internal air flow.
 
Rob Gaskin said:
:thumbs:
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I'm not really sure I know how it works :)
both the breather and the vent are connected to the air cleaner - (one inside, the other outside the filter).
some clever valve stuff must be going on to show a vacuum to the vent but not the breather.
 
So the 2 breathers go either side of the butterfly. 1 on the balance pipe and one into the air filter box. Filtered air at air cleaner to rocker cover and PCV valve in balance pipe to lower crankcase. Yes? Will this not make the mixture lean as your putting unmetered air into the engine?
 
Found this in an 'Autobooks' 260Z manual:
 

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There are K & N filters available for both rocker box and crankcase PCV spigots. Lower crankcase ventilation is surely an anti-pollution device and will contaminate the intake air to an extent.
 
Yes Mike, I think it will add an oil mist to the intake but is that really a bad thing. 2 strokes survive. I think positive crankcase ventilation has more good point than bad IMO. It certainly assists in removing water from oil in a similar way to an extractor in your bathroom.

I looked into using an oil catch tank on my 1jz a while back but doing so would create far too many problems. In modern engines it is designed to remove oil from the head so you don't starve the bearings of oil. Remove this airflow and you will need to address alternative ways of getting oil back to the sump quick enough. Not sure this applies to and l-series though with the timing chain hole but it is very common on timing belt cars.
 
Both mine are vented to a catch tank John, with no running issues. Of course my engine is very different to yours.
 
I can see the reasoning for a catch tank on a race car. I'm also not sure that you would actually notice any difference between a crankcase air circulation system and just venting both to the same pot. The pipes are connected to different parts of the induction system in order to create specific airflow within the engine.

Maybe I'm just trying a little too hard to put the system back together in the best way possible. This has all started from me not being able to start my engine after pulling all the US smog stuff off the car and looking at what to do about all the vacuum leaks.

Anyway, thanks for all the input but I've just bought another sump for the 3uz so I'll be back on that soon.
 
racer said:
Both mine are vented to a catch tank John, with no running issues. .......
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Mine were on my old car, no problem, no oil caught (just a bit of oil condensation) and no oil consumption issues either.
 
You realise there were factory instructions/recommendations regarding sporting/race use and engine breathers, and with factory parts to suit, right...?
 
Albrecht said:
You realise there were factory instructions/recommendations regarding sporting/race use and engine breathers, and with factory parts to suit, right...?
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Alan, no I wasn't aware however I'm sure it was more expensive and complicated than my water bottle and 'Y' pipe. I would be interested in learning more though.
 
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