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Pro/Con of combining valve cover and engine breathers


zredbaron

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Well, I searched and searched and was inundated with unrelated results. It's almost embarrassing to ask! Ok it totally is.

 

What I want to achieve:

To minimize the visibility of these hoses and filters without compromising engine requirements. Race motor, in the off-chance that is a factor.

 

I basically have them joining at a T-junction under my air box, where the hose is then routed into the transmission tunnel and a small 1" universal filter is attached. Pics of my tentative approach below.

 

Any issues with doing this? Does it matter that the filter is several feet downstream? I previously followed a mechanic's advice and had the block breather closed off, but decided to go back to the original design and trust the engineers.

 

I considered routing them into the air box, but didn't want to fabricate supports at this time. In the future, would feeding the hoses to an air box be "more ideal" or irrelevant?

 

Thanks!

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Edited by zredbaron
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Do you not find the filter gets clogged up with oil?  I have pretty much the same set up as you, but the hoses run into an oil catch can with a filter on it.  There isn't a huge amount of oil that collects there, but there is some...

As for the answer to your question... no idea.  Will be interested to hear what the experts have to say.

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Let's be clear about this me thing. Crank case venting is very important to your engine oil health and longevity. How you do it is up to you and yes it involves oil mist that would be nice to catch or separate.

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Let's be clear about this me thing. Crank case venting is very important to your engine oil health and longevity. How you do it is up to you and yes it involves oil mist that would be nice to catch or separate.

 

Awesome, this is exactly the answer I was hoping for! :) I appreciate the reply, good sir.  (Though I don't follow the "me thing" comment?)

 

ryant67, yes the filter ends up being an oily filter, but I found that if the filter end of the hose is mounted in a climbing orientation, the hose seems to serve as the catch can. Perhaps this is sloppy? Just trying to keep it simple.

Edited by zredbaron
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I've ran my with cam cover and crankcase breather hoses joining together and feeding into a catch tank with the tank vented to atmosphere for over 4 years now, no issues to report after numerous on track activities, not had to drain anything out of the catch tank either  

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I've run triple sidedrafts with a pcv system with no problem. Although with a big cam you might need a vacuum reservoir with a check valve. Are you able to use factory power brakes? Turbo engines need to preserve negative pressure functions even under boost so you should be to at atmospheric pressure. But if traditional pcv system doesn't work then source your vacuum from the collector (and dump it into the high temp exhaust gasses to be rid of it, although burning as a combustion additive regulated through pcv valve is cleaner). Regardless, the valve cover port is for filtered fresh air coming in. I like to run an intake hose (after a 90 degree bend) away from that port at an incline and place its breather filter along the firewall (vertically oriented). It's less messy and preserves some oil vapor. But it could instead be plumbed from the filtered side of your airbox. It should not be hooked directly to the crankcase vapor outlet. That would unbalance vapor pressure and flow which would not serve any purpose and would potentially cause power-robbing increased crankcase pressure instead. The crankcase vent outlet is off of the block and is not just a passive vent, it has an evacuating function to respond to increased crankcase pressures due to high engine speeds. The pcv valve regulates blow-by pressure build up while conserving and recovering oil vapor instead of wasting it, keeping gaskets from spewing oil, and making sure that the air that enters the crankcase is clean, filtered air. And not some backwash air sucked in from under the chassis somewhere. Old cars used to have a wire mesh filter on the intake side of the crankcase and a road-draft tube to evacuate. That tube exited down by the trans and was cut at an angle on the end such that increased vehicle speed increased the negative pressure on the system (and let oil vapors spew into the vehicle slipstream).

 

There are no good reasons to do away with emission controls as basic as pcv and evaporative emissions. I'm including collector suction devices too as pcv regulators (if you have a low or wildly fluctuating vacuum signal).

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Just be careful with the exhaust bung as far as blowing smoke is concerned. Depending on the corner worker or whatever it is in autocross, they may have a hissy fit for some light smoke or smell but I doubt it will be a problem.

 

On my Datsun Pickup I have the valve cover to the air filter on the carb (you can use one of those little filters too), and the crank case to the manifold with a PCV valve between. Works just fine and everything is oil free!

 

On the 240Z I had a little filter on the crank case and the valve cover and I had oily residue over everything after a few months of daily driving. The little filters were dripping with oil.

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  • 7 months later...

I found that using my vacuum log to hook up my pcv was great until my MAP sensor at the bottom of my log collected all my blow by. I was not running a catch can, but I will now. I do run my motor hard , so some blow by is to be expected.

I have to make a significant mixture change on the triples when using a pcv vs. not using one.

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