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How Does the Twin Cam Engine Venting System Work?

Started by Ohio HD, May 24, 2022, 10:18:04 PM

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kd

Quote from: Ohio HD on May 27, 2022, 07:24:45 AM
Quote from: turboprop on May 27, 2022, 06:48:45 AM
Quote from: Ohio HD on May 26, 2022, 07:39:15 PM
Quote from: kd on May 26, 2022, 07:29:12 PMIf you are using an automotive PCV valve test it first.  For the most part, they are not a positive seal and will actually breath both ways. (one way is more like a leak)  If you want to hold negative crankcase pressure it may not perform the way you want.

S&S one way check valves.


You cannot see attachments on this board.

How do you intend to route the lines and what are they going to?

Have you seen the video by Tom Reiser on using the oil tank as a catch can and then venting the tank? He wants to drill the trans case (M8 application) for the oil return. There are other ways to do this. For example on an earlier TC the trans case has a plugged hole on top right behind the engine. The vent line could go into that and then drill/tap the oil spout for a vent line. I have been thinking of leveraging this against the Torque-A-Hoe bike and eliminating the external catch can. Only drawback I see is not being able to monitor what is coming out of the vents, but it should result in a much cleaner exterior, specially after extended high speed touring.

That concept of taking the discharge from the heads to essentially the oil pan via the transmission case has me thinking. It would be a nice clean system regarding making it a closed system as it really should be. I agree about being in the blind as far as being able to see what happens at times. Currently I planned to go from heads to catch can.

I had always planned to drill and tap the oil inlet opening at the transmission oil filler neck while everything is apart. That way if I did decide to vent from the transmission case, I just remove a cap and connect a hose.

I have a few questions about what I can do with and around the transmission case. To the point I bought a damaged six speed case to learn from. I should have that on Tuesday next week. Pinwall Cycle is in Ohio, and ships pretty quick.

Updated: they already shipped yesterday, and it should be here today.

I'm going to look for the TR video, thanks for the heads up.



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Here's a consideration.  Rocker box to catch can, catch can vent to filler neck.  Best of both worlds.  The catch can is a mid flow monitor station but doesn't vent to atmosphere. I would even guess you could split the return line to the filler neck to fit a gauge to read crankcase pressure for OCD checks of engine conditions.
KD

turboprop

Quote from: Ohio HD on May 27, 2022, 07:24:45 AM
Quote from: turboprop on May 27, 2022, 06:48:45 AM
Quote from: Ohio HD on May 26, 2022, 07:39:15 PM
Quote from: kd on May 26, 2022, 07:29:12 PMIf you are using an automotive PCV valve test it first.  For the most part, they are not a positive seal and will actually breath both ways. (one way is more like a leak)  If you want to hold negative crankcase pressure it may not perform the way you want.

S&S one way check valves.


You cannot see attachments on this board.

How do you intend to route the lines and what are they going to?

Have you seen the video by Tom Reiser on using the oil tank as a catch can and then venting the tank? He wants to drill the trans case (M8 application) for the oil return. There are other ways to do this. For example on an earlier TC the trans case has a plugged hole on top right behind the engine. The vent line could go into that and then drill/tap the oil spout for a vent line. I have been thinking of leveraging this against the Torque-A-Hoe bike and eliminating the external catch can. Only drawback I see is not being able to monitor what is coming out of the vents, but it should result in a much cleaner exterior, specially after extended high speed touring.

That concept of taking the discharge from the heads to essentially the oil pan via the transmission case has me thinking. It would be a nice clean system regarding making it a closed system as it really should be. I agree about being in the blind as far as being able to see what happens at times. Currently I planned to go from heads to catch can.

I had always planned to drill and tap the oil inlet opening at the transmission oil filler neck while everything is apart. That way if I did decide to vent from the transmission case, I just remove a cap and connect a hose.

I have a few questions about what I can do with and around the transmission case. To the point I bought a damaged six speed case to learn from. I should have that on Tuesday next week. Pinwall Cycle is in Ohio, and ships pretty quick.

Updated: they already shipped yesterday, and it should be here today.

I'm going to look for the TR video, thanks for the heads up.



You cannot see attachments on this board.

There is a piece of the puzzle in each of these three videos. Can certainly be done with hardware sourced elsewhere but he does a god job of explaining everything.









'We' like this' - Said by the one man operation.

Ohio HD

Quote from: rigidthumper on May 27, 2022, 04:54:41 AMAre you going to drill & tap the head, or the rockerbox?

The upper rocker box, high as I can on the intake sides. over the rocker arm.

Ohio HD

Quote from: turboprop on May 27, 2022, 01:45:15 PM
Quote from: Ohio HD on May 27, 2022, 07:24:45 AM
Quote from: turboprop on May 27, 2022, 06:48:45 AM
Quote from: Ohio HD on May 26, 2022, 07:39:15 PM
Quote from: kd on May 26, 2022, 07:29:12 PMIf you are using an automotive PCV valve test it first.  For the most part, they are not a positive seal and will actually breath both ways. (one way is more like a leak)  If you want to hold negative crankcase pressure it may not perform the way you want.

S&S one way check valves.


You cannot see attachments on this board.

How do you intend to route the lines and what are they going to?

Have you seen the video by Tom Reiser on using the oil tank as a catch can and then venting the tank? He wants to drill the trans case (M8 application) for the oil return. There are other ways to do this. For example on an earlier TC the trans case has a plugged hole on top right behind the engine. The vent line could go into that and then drill/tap the oil spout for a vent line. I have been thinking of leveraging this against the Torque-A-Hoe bike and eliminating the external catch can. Only drawback I see is not being able to monitor what is coming out of the vents, but it should result in a much cleaner exterior, specially after extended high speed touring.

That concept of taking the discharge from the heads to essentially the oil pan via the transmission case has me thinking. It would be a nice clean system regarding making it a closed system as it really should be. I agree about being in the blind as far as being able to see what happens at times. Currently I planned to go from heads to catch can.

I had always planned to drill and tap the oil inlet opening at the transmission oil filler neck while everything is apart. That way if I did decide to vent from the transmission case, I just remove a cap and connect a hose.

I have a few questions about what I can do with and around the transmission case. To the point I bought a damaged six speed case to learn from. I should have that on Tuesday next week. Pinwall Cycle is in Ohio, and ships pretty quick.

Updated: they already shipped yesterday, and it should be here today.

I'm going to look for the TR video, thanks for the heads up.



You cannot see attachments on this board.

There is a piece of the puzzle in each of these three videos. Can certainly be done with hardware sourced elsewhere but he does a god job of explaining everything.











Thanks, just got back home. I'll view these shortly.


Ohio HD

 Well, the case arrived already. My UPS woman just shakes her head at me and laughs. She a really good person, always takes care of my packages if rain or snow is in the forecast.

She'll shake ammo boxes and say, you get some nine's  ?    :teeth:


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Ohio HD

Quote from: Ohio HD on May 27, 2022, 02:38:52 PM
Quote from: turboprop on May 27, 2022, 01:45:15 PM
Quote from: Ohio HD on May 27, 2022, 07:24:45 AM
Quote from: turboprop on May 27, 2022, 06:48:45 AM
Quote from: Ohio HD on May 26, 2022, 07:39:15 PM
Quote from: kd on May 26, 2022, 07:29:12 PMIf you are using an automotive PCV valve test it first.  For the most part, they are not a positive seal and will actually breath both ways. (one way is more like a leak)  If you want to hold negative crankcase pressure it may not perform the way you want.

S&S one way check valves.


You cannot see attachments on this board.

How do you intend to route the lines and what are they going to?

Have you seen the video by Tom Reiser on using the oil tank as a catch can and then venting the tank? He wants to drill the trans case (M8 application) for the oil return. There are other ways to do this. For example on an earlier TC the trans case has a plugged hole on top right behind the engine. The vent line could go into that and then drill/tap the oil spout for a vent line. I have been thinking of leveraging this against the Torque-A-Hoe bike and eliminating the external catch can. Only drawback I see is not being able to monitor what is coming out of the vents, but it should result in a much cleaner exterior, specially after extended high speed touring.

That concept of taking the discharge from the heads to essentially the oil pan via the transmission case has me thinking. It would be a nice clean system regarding making it a closed system as it really should be. I agree about being in the blind as far as being able to see what happens at times. Currently I planned to go from heads to catch can.

I had always planned to drill and tap the oil inlet opening at the transmission oil filler neck while everything is apart. That way if I did decide to vent from the transmission case, I just remove a cap and connect a hose.

I have a few questions about what I can do with and around the transmission case. To the point I bought a damaged six speed case to learn from. I should have that on Tuesday next week. Pinwall Cycle is in Ohio, and ships pretty quick.

Updated: they already shipped yesterday, and it should be here today.

I'm going to look for the TR video, thanks for the heads up.



You cannot see attachments on this board.

There is a piece of the puzzle in each of these three videos. Can certainly be done with hardware sourced elsewhere but he does a god job of explaining everything.











Thanks, just got back home. I'll view these shortly.



I may select a spot in the transmission case to drill and tap for hoses coming from the top end. If I don't use that method, I can always just put two pipe plugs in the transmission. Well and a third tapped hole near the oil fill for the new breather outlet. It can also be plugged if not used.

The only issue I can see with dumping the vents into the oil pan is you're potentially dropping water droplets into the oil if you get a lot of condensation in your area. I can park mine after a hot days ride. If it cools off overnight, I get more condensation in the rocker covers. When I start the motor it starts sending water droplets to the catch can, what doesn't burn off as the motor warms up.   

Think about the PCV valve system in cars. Some end up with the milky brown oil gunk in the valve and valve covers. That's water and oil mixing, or trying to mix.



Hossamania

My thought as well, I'm not a fan of running the vents back into the oil pan, I've seen what can come out of those hoses.
If the government gives you everything you want,
it can take away everything you have.

kd

It is fairly common to run a can to catch the sludge and acidic discharge then pass the gasses back into the crankcase (or in this case oil reservoir).  The bad part is because it is then a truly closed system condensed air that carries moisture stays in the sealed atmosphere and becomes acidic. 

My can is from a 5.7 Hemi and it works like that but the fumes eventually got delivered to the intake without the oil sludge load. Venting it high after the can makes more sense to me to keep the pistons clean of carbon but the EPA doesn't think so.

I have a low mounted can and a stainless vent line up and then down.  Any residual moisture leaves as a gas vapor and moisture runs back down until it becomes vapor and leaves on its own.  The line doesn't drip.
KD

Ohio HD

May 28, 2022, 09:05:32 PM #33 Last Edit: May 28, 2022, 10:40:26 PM by Ohio HD
I'm pretty sure I'm going to stay with the conventional catch can like I have on the current 124". No chance that anything gets back into the motor. I don't loose any oil through the vents anyway.

I expect the same behavior with the new 124".


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Wookie3011

When I had the motor out, I considered tapping the top trans cover to run my breathers into it. I found a gasket inside of the cover. I wasn't sure exactly what the gasket was for? Was it to keep a certain amount of pressure or just a oil seal? I backed out of doing it. My current vent system is 3/8 out the breather bolts. I bored out the breather bolts and opened up the holes hair more. With the venting system, how can I promote good vacuum for ring seal and to prevent ring flutter while still releasing pressures? Is this the primary purpose of the S&S valve? Does venting to atmosphere hurt vacuum potentially in a open system without this valve?

Ohio HD

The S&S valve is used when you remove the OEM breathers internal to the rocker box on top of the head. I won't be using the OEM breathers.

My head porter recommended that I use the S&S valves and place the oil lines as high as possible in the rocker box. He knows much more than I do.

Ohio HD

Permanently blocked off the lower breather plate of early style Twin Cam breathers.

Tapped for 1/4 NPT, plug was liberally coated with high Strength Sleeve Retainer. I doubt you could get it out 24 hours from now. If you did, the part would be warped from the heat.



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turboprop

As a result of this thread, I had a look at the two TC124s in my FXRs to see if this setup could be leveraged against them. Not needed at this point, but curious. I did not lift the tank and hold hardware in place, just sort of eyeballed it (VROM?). Seems that if one were to use the fittings and location shown earlier, that both lines would be obstructed by the mount for the upper link. Maybe not. I have a bunch of 6AN fittings to include some 90s and 220s(?) that might work better. I have a TC bagger but have never looked under the tank. Go figure.
'We' like this' - Said by the one man operation.

Ohio HD

Quote from: turboprop on May 29, 2022, 03:10:31 PMAs a result of this thread, I had a look at the two TC124s in my FXRs to see if this setup could be leveraged against them. Not needed at this point, but curious. I did not lift the tank and hold hardware in place, just sort of eyeballed it (VROM?). Seems that if one were to use the fittings and location shown earlier, that both lines would be obstructed by the mount for the upper link. Maybe not. I have a bunch of 6AN fittings to include some 90s and 220s(?) that might work better. I have a TC bagger but have never looked under the tank. Go figure.

Yeah, your setup has different restrictions as far as rocker box access. Is there room above the rocker box and the gas tank? You could use an AN6 x 1/8 pipe with a 90°. That would keep the required access height lower under the tank. Or send the AN6 connection to the right of the bike.


 

Ohio HD

Quote from: Wookie3011 on May 28, 2022, 11:24:24 PMWhen I had the motor out, I considered tapping the top trans cover to run my breathers into it. I found a gasket inside of the cover. I wasn't sure exactly what the gasket was for? Was it to keep a certain amount of pressure or just a oil seal? I backed out of doing it. My current vent system is 3/8 out the breather bolts. I bored out the breather bolts and opened up the holes hair more. With the venting system, how can I promote good vacuum for ring seal and to prevent ring flutter while still releasing pressures? Is this the primary purpose of the S&S valve? Does venting to atmosphere hurt vacuum potentially in a open system without this valve?

I'm going to drill and tap the transmission case for venting to the oil pan, and for venting from the oil fill. I'll plug them for now, but they'll be there if I need or want to use them.

turboprop

Quote from: Ohio HD on May 29, 2022, 05:56:30 PM
Quote from: Wookie3011 on May 28, 2022, 11:24:24 PMWhen I had the motor out, I considered tapping the top trans cover to run my breathers into it. I found a gasket inside of the cover. I wasn't sure exactly what the gasket was for? Was it to keep a certain amount of pressure or just a oil seal? I backed out of doing it. My current vent system is 3/8 out the breather bolts. I bored out the breather bolts and opened up the holes hair more. With the venting system, how can I promote good vacuum for ring seal and to prevent ring flutter while still releasing pressures? Is this the primary purpose of the S&S valve? Does venting to atmosphere hurt vacuum potentially in a open system without this valve?

I'm going to drill and tap the transmission case for venting to the oil pan, and for venting from the oil fill. I'll plug them for now, but they'll be there if I need or want to use them.


A 90 degree adapter fitting into the top cover would certainly work. I am stupid sometimes. I had a 90 degree hose end sort of held in place and thinking it was too tight. But duhh, a 90 degree adapter and a straight hose end would work very well. Based on your results, I might give this a try.  Thanks. Learning has occurred.
'We' like this' - Said by the one man operation.

Ohio HD

Quote from: turboprop on May 30, 2022, 04:45:55 PM
Quote from: Ohio HD on May 29, 2022, 05:56:30 PM
Quote from: Wookie3011 on May 28, 2022, 11:24:24 PMWhen I had the motor out, I considered tapping the top trans cover to run my breathers into it. I found a gasket inside of the cover. I wasn't sure exactly what the gasket was for? Was it to keep a certain amount of pressure or just a oil seal? I backed out of doing it. My current vent system is 3/8 out the breather bolts. I bored out the breather bolts and opened up the holes hair more. With the venting system, how can I promote good vacuum for ring seal and to prevent ring flutter while still releasing pressures? Is this the primary purpose of the S&S valve? Does venting to atmosphere hurt vacuum potentially in a open system without this valve?

I'm going to drill and tap the transmission case for venting to the oil pan, and for venting from the oil fill. I'll plug them for now, but they'll be there if I need or want to use them.


A 90 degree adapter fitting into the top cover would certainly work. I am stupid sometimes. I had a 90 degree hose end sort of held in place and thinking it was too tight. But duhh, a 90 degree adapter and a straight hose end would work very well. Based on your results, I might give this a try.  Thanks. Learning has occurred.

I've always liked that phrase.

JSD


Quote from: 60Gunner on May 25, 2022, 04:11:34 PMThing is,it's a compounding issue. The stock setup is marginally good enough...for a stock bike.
There's way better alternatives. Crankcase breathing has never been a strong suit for Harleys.
Use a good external reed valve. They close quicker and don't allow ANY air back in that builds pressure. They also don't dry out and fail to seal at all.
I don't get a drop of oil out of mine. My umbrella valves are removed. The stamped housings are still there, empty, to aid in oil separation.

Drill the return holes under them to 1/8".
A picture of external reed valve please. 

60Gunner

June 04, 2022, 07:59:32 PM #43 Last Edit: June 04, 2022, 08:16:47 PM by 60Gunner
Quote from: JSD on May 30, 2022, 10:12:00 PM
Quote from: 60Gunner on May 25, 2022, 04:11:34 PMThing is,it's a compounding issue. The stock setup is marginally good enough...for a stock bike.
There's way better alternatives. Crankcase breathing has never been a strong suit for Harleys.
Use a good external reed valve. They close quicker and don't allow ANY air back in that builds pressure. They also don't dry out and fail to seal at all.
I don't get a drop of oil out of mine. My umbrella valves are removed. The stamped housings are still there, empty, to aid in oil separation.

Drill the return holes under them to 1/8".
A picture of external reed valve please.


This is the actual reed valve used in the BMW twins.




This is the machined housing the valves are in. It can used in line or as a case mount by changing the fittings. I'm working on the best case mount location. I'll drill/tap a hole once I come up with the best location but for now this works really well. I've actually got it shortened up more and they're barely visible behind the AC. The case mount version of this is used on Norton twins. I never cared for breathing from the heads. My sporty build was from the cam chest. Drill/tapped a hole in the cam cover at the 2 o'clock position. Totally hidden by the front pipe.


Don D

Harley goes to great trouble (and expense) to also provide oil separation from the vented air. The system works fair at best but we push it's capabilities with modified engines. A one way valve just controls the backflow of the vented air. Oil carryover must be controlled and that can be accomplished by the choice where to tap which is out of the windage or Harleys method by employing separation. Let the pressure out and keep the oil in.

60Gunner

June 05, 2022, 07:27:18 AM #45 Last Edit: June 05, 2022, 08:31:35 AM by 60Gunner
Quote from: turboprop on May 27, 2022, 06:48:45 AM
Quote from: Ohio HD on May 26, 2022, 07:39:15 PM
Quote from: kd on May 26, 2022, 07:29:12 PMIf you are using an automotive PCV valve test it first.  For the most part, they are not a positive seal and will actually breath both ways. (one way is more like a leak)  If you want to hold negative crankcase pressure it may not perform the way you want.

S&S one way check valves.


You cannot see attachments on this board.

How do you intend to route the lines and what are they going to?

Have you seen the video by Tom Reiser on using the oil tank as a catch can and then venting the tank? He wants to drill the trans case (M8 application) for the oil return. There are other ways to do this. For example on an earlier TC the trans case has a plugged hole on top right behind the engine. The vent line could go into that and then drill/tap the oil spout for a vent line. I have been thinking of leveraging this against the Torque-A-Hoe bike and eliminating the external catch can. Only drawback I see is not being able to monitor what is coming out of the vents, but it should result in a much cleaner exterior, specially after extended high speed touring.

I'm not sure I'd want to return all that nasty crud to my oil tank/pan. It should burn off but...

That S&S valve looks like a copy of the one used by the Mercedes kompressor engines before the turbo. It's my understanding they're quick acting enough to work well for this application and can be had for under $10. Just not sure how well they hold up. Most automotive breather valves, especially PCVs, have an extremely short life expectancy. They can't handle the rapid pulses.
I'd like to see the actual valve in those S&S breathers.
Quote from: HD Street Performance on June 05, 2022, 05:48:57 AMHarley goes to great trouble (and expense) to also provide oil separation from the vented air. The system works fair at best but we push it's capabilities with modified engines. A one way valve just controls the backflow of the vented air. Oil carryover must be controlled and that can be accomplished by the choice where to tap which is out of the windage or Harleys method by employing separation. Let the pressure out and keep the oil in.

This is why I haven't vented from the cases...yet. I had a good location on my sporty and had 1/8npt X hose barb 90° baffled inside the cam cover. It worked quite well for oil separation. I just haven't given it enough thought on this twin cam...yet. But I will.

A visit to some other twin forums with giant air pumps like our engines and you'd see they pretty much laugh at Harley's umbrella valves.
Reed valves are way better at keeping a slight vacuum. 
The location (heat) doesn't do umbrella valves any favors tho.

The benefits are obvious. Better ring seal which means less pressure in the first place is a good enough reason for me tho.
These reed valves are obviously getting it done as my ring seal is outstanding. Did a compression test last week and while the calculators say my ccp should be around 207, it's just short of 215psi cold. I'll call it 212. Both cylinders are identical.

The best location for crankcase venting is closer to the source of the pressure imo. That would be the cases like they use to be before the EPA bs and venting back to the intake became mandatory. It would aid in oil return from the heads too.

Ohio HD

Quote from: 60Gunner on June 05, 2022, 07:27:18 AMThat S&S valve looks like a copy of the one used by the Mercedes kompressor engines before the turbo. It's my understanding they're quick acting enough to work well for this application and can be had for under $10. Just not sure how well they hold up. Most automotive breather valves, especially PCVs, have an extremely short life expectancy. They can't handle the rapid pulses.
I'd like to see the actual valve in those S&S breathers.

Whether Mercedes, S&S or whom ever uses these one way check valves, you can be sure they're made for industrial and medical use as a common type of valve. Neither Mercedes or S&S manufacture these valves.

They're commonly available with extremely low cracking pressure, as low as 1 to 3 PSI to seal them. Seal materials are commonly Viton, Buna or Silicon. They respond extremely fast due to the free floating diaphragm seal and seat design.


Coming from an industrial facilities background, as well as automation machine tool manufacturer, I've seen these types of valves work in poor factory conditions for many years before replacement.

What data do you have on life expectancy of these valves in cycles, and the actual cause of failure? By the way these are not automotive PCV valves.

60Gunner

Quote from: Ohio HD on June 05, 2022, 02:12:01 PM
Quote from: 60Gunner on June 05, 2022, 07:27:18 AMThat S&S valve looks like a copy of the one used by the Mercedes kompressor engines before the turbo. It's my understanding they're quick acting enough to work well for this application and can be had for under $10. Just not sure how well they hold up. Most automotive breather valves, especially PCVs, have an extremely short life expectancy. They can't handle the rapid pulses.
I'd like to see the actual valve in those S&S breathers.

Whether Mercedes, S&S or whom ever uses these one way check valves, you can be sure they're made for industrial and medical use as a common type of valve. Neither Mercedes or S&S manufacture these valves.

They're commonly available with extremely low cracking pressure, as low as 1 to 3 PSI to seal them. Seal materials are commonly Viton, Buna or Silicon. They respond extremely fast due to the free floating diaphragm seal and seat design.


Coming from an industrial facilities background, as well as automation machine tool manufacturer, I've seen these types of valves work in poor factory conditions for many years before replacement.

What data do you have on life expectancy of these valves in cycles, and the actual cause of failure? By the way these are not automotive PCV valves.

I wasn't implying those WERE pcv valves.
Extensive testing by several of us sporty guys 6 or 7 years ago is my experience with a variety of one way breather valves. No automotive PCV valve ever held up, at least not for long, in this application. The springs don't hold up. Others are not fast acting and can't keep up with the rapid pulses and allow air back in.
 An automotive application is far different and less demanding when there's just as many pistons going up, basically canceling out the ones going down at any given time,  as opposed to 2 going up and down at nearly the same time or in the case of a BMW twin at exactly the same time.
The XL forums has a huge database of all the testing we did, including slack tube testing and tutorials with pics on how to install the ultimate crankcase vent. My Sporty mod that a lot of them are running in one variation or another is there in detail.
No one that has done it has ever gone back to breathing from the heads. But twin cams are a different animal.
I could kick myself for not going gear drive cams tho. The DT cam plate I'm running has a labyrinth that separates air from oil. It's why this pump/plate eliminates aeration of the oil as I understand it.  R&R also has a cam cover that integrates with the plate and has a built in breather location that ties into this and solves the air/oil separation issue breathing from the cam chest. This cover only works with gear drive cams tho as it uses all the same bolt holes as the cam plate. How well it all works I don't know but I sure would've liked to have found out. According to one of the guys at R&R it works well.

This particular reed valve has been tested in street and track BMWs and why I chose it and its used in Norton twins now as well.
It's not cheap tho.


Ohio HD

Quote from: 60Gunner on June 06, 2022, 03:16:07 AM
Quote from: Ohio HD on June 05, 2022, 02:12:01 PM
Quote from: 60Gunner on June 05, 2022, 07:27:18 AMThat S&S valve looks like a copy of the one used by the Mercedes kompressor engines before the turbo. It's my understanding they're quick acting enough to work well for this application and can be had for under $10. Just not sure how well they hold up. Most automotive breather valves, especially PCVs, have an extremely short life expectancy. They can't handle the rapid pulses.
I'd like to see the actual valve in those S&S breathers.

Whether Mercedes, S&S or whom ever uses these one way check valves, you can be sure they're made for industrial and medical use as a common type of valve. Neither Mercedes or S&S manufacture these valves.

They're commonly available with extremely low cracking pressure, as low as 1 to 3 PSI to seal them. Seal materials are commonly Viton, Buna or Silicon. They respond extremely fast due to the free floating diaphragm seal and seat design.


Coming from an industrial facilities background, as well as automation machine tool manufacturer, I've seen these types of valves work in poor factory conditions for many years before replacement.

What data do you have on life expectancy of these valves in cycles, and the actual cause of failure? By the way these are not automotive PCV valves.

I wasn't implying those WERE pcv valves.
Extensive testing by several of us sporty guys 6 or 7 years ago is my experience with a variety of one way breather valves. No automotive PCV valve ever held up, at least not for long, in this application. The springs don't hold up. Others are not fast acting and can't keep up with the rapid pulses and allow air back in.
 An automotive application is far different and less demanding when there's just as many pistons going up, basically canceling out the ones going down at any given time,  as opposed to 2 going up and down at nearly the same time or in the case of a BMW twin at exactly the same time.
The XL forums has a huge database of all the testing we did, including slack tube testing and tutorials with pics on how to install the ultimate crankcase vent. My Sporty mod that a lot of them are running in one variation or another is there in detail.
No one that has done it has ever gone back to breathing from the heads. But twin cams are a different animal.
I could kick myself for not going gear drive cams tho. The DT cam plate I'm running has a labyrinth that separates air from oil. It's why this pump/plate eliminates aeration of the oil as I understand it.  R&R also has a cam cover that integrates with the plate and has a built in breather location that ties into this and solves the air/oil separation issue breathing from the cam chest. This cover only works with gear drive cams tho as it uses all the same bolt holes as the cam plate. How well it all works I don't know but I sure would've liked to have found out. According to one of the guys at R&R it works well.

This particular reed valve has been tested in street and track BMWs and why I chose it and its used in Norton twins now as well.
It's not cheap tho.



Lets keep the discussion to what we're "using" then and not confuse everyone with "automotive PCV" that no one is using in this post.

At the end of the day the valve style has nothing to do with oil expelling from the head. The valves job is to stop reverse flow of air from entering the head, and then allowing air to exit when the internal direction of flow changes in the motor. You get oil expelling when the head can't drain fast enough, or is being over loaded by internal motor issues or components. In those cases the valves become exposed to more oil than they should. 

S&S started using these check valves several years ago with their cylinder heads and with their crate motors. They however use one valve for the entire motor.






 

Don D

"You get oil expelling when the head can't drain fast enough, or is being over loaded by internal motor issues or components."

The location of where venting is tapped matters. There are many places that have a lot of oil windage that are not suitable to use to relieve pressure without guarding or other means of oil separation. These conditions are prevalent all the Harley big twins even on motors that have no issues.