Crankcase breather

[joe newsom]

Any suggestions on aftermarket air filter and crank case breather. I was considering using the stock air cleaner. But as my engine is coming together I am re thinking that. I have seen some nice pics of aftermarket filters.

I will be running SU Carbs from Ztherapy

 

 

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[Chickenman]

Run the stock Datsun PCV system. It works, very, very well.

The crankcase breather Tube connects to the PCV Valve at the bottom of the Intake manifold.  It has a built in oil baffle and screen inside the block.  It is very effective at catching and separating oil droplets. The Vent on top of the Valve cover goes to the stock Air cleaner. The hose to the Air Cleaner plays a more important part than people often realise. The Arrington CCV Bible article explains why. 

You should always run an operational PCV system on a street car. Failure to do so will cause fairly quick contamination of the oil via ring blowby, acid accumulation in the oil due to water condensation not being removed effectively by Vent To Atmosphere systems. Increased  oil leaks from seals and gaskets due to the fact that you will be running a higher positive crankcase pressure with out a PCV valve.  And often over looked. You get increased Ring seal by running a PCV system compared to a VTA system.

If you like, you can run a closed Catch can system between the Block breather hose and the PCV Valve. But it must be a sealed or " recirculating " Catch Can system. That means no Vent on top of the Catch can. Doing so renders the PCV system virtually inoperative and you are back to a VTA system. Which should not be run on a Daily Driver..

Race cars are a different deal for several reasons:

1: The oil is changed much more regularly than a street car. Professional Road Race cars may change oil after every race. Contaminants would never have a chance to build up as in a street car.

2: Race cars, particularly Circuit racers, run long enough and hot enough to burn off any water condensation that will forms acids and sludge in the oil. Short drives to the 7/11 on a Daily driver don't get hot enough to burn off the water condensation. That is the job of the PCV system.

3: Circuit race cars usually run a Dry Sump system for oiling. The scavenge pumps create a negative pressure in the even at High RPM. This is very effective at increasing ring seal. Nascar engines have seen HP gains all the way up to 20 in/hg vacuum in the block. 

This CCV article from Arrington Performance explains the functions and benefits of proper Cranck case Ventilation. Which on street cars is provided by the PCV system:

 Arrington CCV Bible.pdf

Edited January 1, 2018 by Chickenman

[Chickenman]

Note that in section 4 they discuss the problems of running a PCV Valve on Turbo engines. This only applies to retrofitted Turbo engines. On OEM designed Turbo CCV systems , the Vent routing incorporates one way check valves and specially designed PCV valve to eliminate the problem of pressurizing the crankcase through the CCV system when under boost.

Nissan has done this on the Factory L280 Turbo by using a specific PCV valve for the Turbo motors. This has a silicone sealing lip inside the valve that allows no reverse flow when under boost. This is important to remember if you have an L28 Turbo. ALWAYS buy the Nissan OEM  PCV valve for the Turbo models from a Nissan dealership. Aftermarket valves are often the same part for NA and Turbo models and may not have the silicone sealing ring. 

FYI, VW/Audi 1.8T engines are always had an oil  sludging problem due to a weak PCV system. Quite a few Big Turbo VW/Audi 1.8/2.0 Turbo engine builds are now switching to a design using the the Nissan Turbo PCV valves. The stock VW/Audi valves is made of plastic and is a POS. The all metal Nissan Turbo PCV  valve flows more than the VAG valves, creating more negative pressure in the Cranckcase and  and it reverse seals under Boost better than the VW/Audi PCV valves. Score one for Nissan!!! 

[zKars]

Excellent writeup. How many triple carb setups have I seen with a little K&N filter on the block tube and often the same on the valve cover. 

I just checked Rock Auto's listing for PCV valves for the 83 NA and Turbo models to look for differences.

They list the identical valves for all of the approx 6 manufacturers of valves. Great.....  And while it's "possible" that all these valves meet the turbo sealing spec, I think we know the truth about that...

And to assist with the actual question, once you get your balance tube back on, put the stock PCV valve back in and run the stock PCV hose between the block vent and the PCV valve. Put a little knipple on the back of whatever air cleaner you run and put that hose onto the valve cover. 

Edited January 1, 2018 by zKars

[Stanley]

Not the question you asked but I see you have the stock (hot=closed) manifold heater thermostat attached to the front intake manifold. On the stock 240z that thermostat goes on the back of the rear intake manifold to a steel tube that goes around the back of the motor to heater Y-pipe.   There's a BSPT hose barb that goes on the front.  I think it's a different size hose barb than the one on the thermostat housing so it takes a special hose. All that stuff was available last time I looked. Maybe it wouldn't make any difference where the thermostat is attached (I don't know enough about how it works to say), except the special hose might not fit as well.

[Stanley]

How'd you get the cam cover looking like that?

A quick look at that CCV book told me I don't understand the system as well as I thought.

Edited January 1, 2018 by Stanley

[jitenshakun]

Does anyone happen to know the K&N part numbers for the crankcase and valve cover breathers?  I'd prefer to avoid the zDepot freight and exchange if I can.

[jitenshakun]

Found them.

K&N 62-1340 is the 5/8"
K&N 62-1370 is the 1"

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