Blowby Breather
 

Well the old girl is getting to the point where she has a little blowby. I have a tiny amount of oil that likes to leak out of my brand new valve cover gaskets and sit on the head. I've heard that blowby should be vented from the highest part of the engine, dont know how true that is but it makes since. Anyway my plan is to drill and tap a couple valve covers (2&5) and set them up with a couple breathers. A buddy of mine gave me a fitting that he used for the filter and it works perfect. I'd like to know your thoughts on blowby and the proper way to vent it. Thanks for any input fellas. :c:

Here's the parts
Attachment 41425

There's a breather tube on the drivers side of your block. That's where blow by gets vented. But those vents on the valve covers probably work more efficiently, as well as look trick as all get out! :tu::choochoo:

Yeah i know theres a breather tube down there. Didnt mean it to come across like I didnt know what to do to vent it or how its vented. lol

I would bet that breather clogs up because of the oil residue.

No.... And if it does all i have to do is pull the filter off and clean out the fitting and filter.

Blowby Breather
 

Good possibility it'd clog. They were designed for gas jobs, with the use of a PCV valve the only thing that should make it's way thru that filter is fresh air. Diesels how ever dont "circulate" air thru the crankcase in tue same manner. There will be an oily steam vented thru that filter. How long it'll take to clog... Who knows. Clean it and or replace it periodically; it isn't like they're horribly expensive.


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On my detroit in my freightliner the blowby pipe come out of the valve cover up high on the side but it is just a pipe going down the side of the engine the filter will clog eventually pittsburgh power makes a nice little catch can for big trucks you might look at it to get some ideas

I feel like that will lead to ton of oil mist all over the engine. Could you just feed a pipe into the intake or air inlet hose that would use that oil mist during combustion like a gas engine? Or would that runaway?

Ive seen this done on many trucks and doesn't leave any mist or oil residue.... Its not like this fitting is the size of the valve cover. Its only like half an inch big. Just simply vents the excess pressure under the valve covers caused by higher than normal blowby, simply put. Ill post up some pictures of how to do it and how it turns out. Main thing is to make sure its not in the way of the rocker arms. :scare2:

you look into the Case dual cover breathers? id like to get those someday.

Attachment 41424

WOW! That is awesome! :tu:

The case valve covers are pretty nice. :rocking:


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Those case valve covers are sweet my wife works for the case dealer if you get me a part # I'll get a price

Blowby Breather
 

Part numbers!

Cummins Dual Valve Cover Breather Kit 5.9L Diesel 12 Valve

:tu:

You may save some money going through your local Case dealer, I did.

Thanks my wife gets a good discount for being an employee

What diameter lines come out of that thing?

I want to run a 1/2" Teflon line out of each valve cover, don't know if it'd be enough diameter to actually be worth it...

I don't think you have much oil that's going to come out of there. I can run mine at a couple thousand RPM without valve covers and it doesn't make a mess, the oil just slowly comes up and glistens over everything. But I've had other guys tell me that their engines do make a mess, so it's either a first gen/ second gen difference or my engine has oiling problems in its advanced age.

You definitely don't want to vent them into the air intake; that'll just get oil in the intake valves. That's what new engines do with their PCV stuff, and it sucks horribly. I'd run it down into a cup to catch the condensate and just let it bleed off to the air. And I probably wouldn't use a cup.

The vast majority of blow-by occurs when under a load and is exaggerated with increasing boost. Simply raising the engine rpms isn't going to present with a lot (pending wear on the engine of course).
Those black circular things at the top of the breather is an oil/vapor separator. Any oil entrained with the blow-by gasses is removed by way of impingement and drained directly back into the valve-cover. As such, it has been my experience that very little oil if any goes out the vent pipe.

And I vent mine into the engine's air filter housing with absolutely no oily mess. ;)

Attachment 41369

Blowby throwing oil around the valves and intentional oil spray throwing oil around the valves are two separate things. I've been told that some 6BT's throw oil around the valves intentionally and make a mess if you run them without covers. Mine does not; seems that I could probably drill an open half inch hole in the top of all my valve covers and not have too much of an oily mess. But other people say their's sling oil like crazy. I don't know if my engine's drier up there than normal or not.


You don't want to feed the crankcase breath back into the engine. Even if all the coalescing filter stuff is doing its job and you have no liquid oil in the vapor, it's still hotter than ambient air and short on oxygen. The environmentally conscientious way is to put it into the intake, the longevity or performance concerning way is to vent it to atmosphere. Of course venting it before your air filter isn't going to be a substantial detriment, but why risk blowing oil drops on your filter or just not giving your engine as cool clean air as possible? And I have seen many a 200,000-300,000 mile engine need a valve cleaning due to oil coming through the crankcase ventilation system; one of the benefits of direct injection is that your intake valves stay squeaky clean, why ruin it?

As you well know, ;) the valve-train is lubricated by oil fed up and through the rocker arm pedestals and to the rocker arm shafts and ultimately drips on the valve stems.

That oil drains back to the crankcase by flowing down through the holes in the head/block that contain the valve push-rods. That passage is rather narrow.

When on the throttle hard, producing more blow-by gasses, those gases pass up through those same push-rod tubes. If there's enough blow-by gasses rushing through those tubes (WOT ?), it will entrain some of the draining oil.
Those Case valve-cover separators work very well at separating the entrained oil from the blow-by gases.

Pending the wear on the engine, the amount of boost (blow-by), etc, a little or a lot of oil is picked up.

Certainly those gasses most likely do not support combustion of the fuel, but unless your engine is stupid worn out, it shouldn't (and doesn't IMO) present a problem.

I think with well over 400hp to the ground, taking this 6400# heap for a high 12 second 1/4th mile pass, the blow-by has apparent negligible impact in my case. ;)

If you vented it to atmosphere you'd probably be making 650 HP and running high 9's. :tttt: