Need input on crankcase evacuation remedies

[dontlifttoshift]

So, to make sure I have the flow path right.

Fresh air enters the passenger side valve cover through a small hole. Then it flows through the crankcase to the drivers side valve cover where it is connected to the air oil separator with a 3/8" hose and mounted below the height of the valve cover and then connected to the intake or carb baseplate with another 3/8" hose. Right?

In theory, the crankcase will have negative pressure at idle and cruise but I just don't see one 3/8" hose being enough ventilation at wfo. Crankcase pressure will go positive and it will try to push through the AOS, taking oil with it, and when that's not enough, gaskets will start to leak.

At least that's the way it looks from 500 miles away. I hope it works for you but I think you will want a 5/8" inlet/outlet on the passenger side.

[will69camaro]

David (MightyMouse) is a wealth of knowledge on this. I spoke with him at length before setting up my car.

Have his PCV can on mine with:
-10 from behind air filter to DS valve cover (clean air)
-12 from passenger cover to catch can (dirty air to catch can)
-6 from can to intake through a PCV (clean air return)

Very happy with the look and so far so good for the performance of it.


You can see the -10 on the far side in front of the brake reservoirs, and the -12/can/etc on the passenger side firewall.

[SSLance]

Originally Posted by dontlifttoshift

So, to make sure I have the flow path right.

Fresh air enters the passenger side valve cover through a small hole. Then it flows through the crankcase to the drivers side valve cover where it is connected to the air oil separator with a 3/8" hose and mounted below the height of the valve cover and then connected to the intake or carb baseplate with another 3/8" hose. Right?

In theory, the crankcase will have negative pressure at idle and cruise but I just don't see one 3/8" hose being enough ventilation at wfo. Crankcase pressure will go positive and it will try to push through the AOS, taking oil with it, and when that's not enough, gaskets will start to leak.

At least that's the way it looks from 500 miles away. I hope it works for you but I think you will want a 5/8" inlet/outlet on the passenger side.

You are close except for one part. Should the blow by be more than the 3/8s line can handle from the driver side VC to can, it will then try to exit via the pass side breather as well. If I see sign of oil coming out the pass side breather, I'll up the size of the line from the driver side breather to the can. If you up the size on the pass side, that just makes an easy exit for the blow by air to go that way, which is not what you want.

David at Mighty Mouse says a 3/8s line is good for up to 600 HP generally, but every case is different depending on engine and other variables.

The main difference with his setup is his check valve in the can which takes the place of most PCV valves. It will NOT close off under WOT like most PCV do. This lets the manifold vacuum keep sucking on the crank case even under WOT and that keeps the air flowing in the pass side, out the driver side and the excess that doesn't make it out the check valve to the carb goes up out the breather on top of the can.

[SSLance]

Originally Posted by will69camaro

David (MightyMouse) is a wealth of knowledge on this. I spoke with him at length before setting up my car.

Have his PCV can on mine with:
-10 from behind air filter to DS valve cover (clean air)
-12 from passenger cover to catch can (dirty air to catch can)
-6 from can to intake through a PCV (clean air return)

Very happy with the look and so far so good for the performance of it.

You can see the -10 on the far side in front of the brake reservoirs, and the -12/can/etc on the passenger side firewall.

Sounds like a similar prescription as mine, just upped in size. A little more flow on the dirty out side vs the clean in side which keeps negative pressure in crackcase and air flowing the correct direction.

How much oil do you notice that you accumulate in your can? During every day cruising and also during heavy WOT driving?

[dontlifttoshift]

Should the blow by be more than the 3/8s line can handle from the driver side VC to can, it will then try to exit via the gaskets or seals because little restrictor in passenger side breatheras well.

fixt

Nature abhors a vacuum. If pressure in the crankcase is negative, blow by will never exit the breather on the passenger side.....physics won't allow it.

What will happen at wot, is the negative pressure in the manifold will be lost, consequently the negative pressure in the crankcase will be lost and you _will_ build positive pressure in the crankcase and now it can't breathe out the passenger side. The other issue with restricting the clean air side is when vacuum goes high, like it would in a closed throttle braking zone, it will suck oil into the AOS, far more than if the passenger side breather was open.

I've pushed the rear main seal out of an LS motor that had 2 -6 lines, one in each cover, and the OEM style fixed orifice pcv running from valley to the intake. The -6 lines ran uphill to a vent can mounted on the firewall. A Moroso universal AOS was inline with the dirty side. Before we pushed the main out, we could fill the AOS in a track session and we would get oil in the valve cover vent can as well.

After we replaced the rear main seal, we upsized the valve cover lines and fittings to the vent can to -10. The AOS gets drained at the end of track _days_ now and is less than half full. All that is in the vent can is water vapor usually. It has been this way for 3 years.

Have the tools with you to remove that restrictor.

[SSLance]

I appreciate your concern Donny, I'm learning about all of this from scratch and every bit helps. I know what I had before did not work...and have a pretty good idea why. If I'm correct in that assumption, this should cure my ills.

Originally Posted by dontlifttoshift

What will happen at wot, is the negative pressure in the manifold will be lost, consequently the negative pressure in the crankcase will be lost and you _will_ build positive pressure in the crankcase and now it can't breathe out the passenger side.

If there is enough flow for the pressure to exit the driver's side breather to the catch can, why would its need to exit the pass side also?

Originally Posted by dontlifttoshift

The other issue with restricting the clean air side is when vacuum goes high, like it would in a closed throttle braking zone, it will suck oil into the AOS, far more than if the passenger side breather was open.

I'm not sure why it would suck more oil under that scenario? Foul blow by air is one thing...that needs to leave the crankcase. Extra oil with that blow by is another. David mentioned that something his LS customers that road race deal with is the oil that builds up on top of the head during a long straight at WOT sloshing over the baffle and being blown or sucked into the line to the catch can under hard braking at the end of said straight. This symptom can fill a catch can up during just one session on track.

He doesn't think I'll have that issue because of the extra height from my tall valve covers, we'll see though. That is why I'll have the recirculator top to put on the can with me along with a line ran to a second can if needed.

Originally Posted by dontlifttoshift

Have the tools with you to remove that restrictor.

Not an issue, it can be removed without any tools at all...if needed.

[SSLance]

David said when at warm idle I should just have a bit of vacuum at the breather on the can. With the breather pulled, I can't really feel vacuum with my hand but a piece of tissue confirms there is just a bit of vacuum pulling through the breather. I flushed the cooling system several times today and finished up a few other odds and ends...then beat on the car for a bit after several road tests. I lost 150 RPM at idle... Which is fantastic as the car has always idled fast. Now it idles at a rock steady 810-830 RPM instead of the 970-1020 RPM. No sign of oil out the pass side breather yet, big test will be track day Thursday night.

Here's a little video of me testing out my other favorite off season upgrade. Anyone guess what it is...?

https://youtu.be/AmerrpIqFDo

I'll update how the catch can did after Track Night in America on the newly paved Heartland Park Topeka road course Thursday.

[will69camaro]

Originally Posted by SSLance

Sounds like a similar prescription as mine, just upped in size. A little more flow on the dirty out side vs the clean in side which keeps negative pressure in crackcase and air flowing the correct direction.

How much oil do you notice that you accumulate in your can? During every day cruising and also during heavy WOT driving?

Haven't put many miles on it yet but at 200mi and some of those hard, it had about a tablespoon. It does look nasty what comes out of there.

[SSLance]

Had a blast at the track last night, pics and videos will be posted soon.

Here's what I drained out of the MightyMouse catch can this morning after (3) 20 minute sessions on track at mostly WOT.





Just maybe an ounce or two of gassy smelling water with not even a hint of oil residue on the underside of the breather on the passenger side. Not only that but the engine didn't use or leak a drop of engine oil either. I'm VERY happy with the results of this mod. Not only did it cure a long standing idle problem by blocking a basically wide open vacuum leak but it also fixed the oil mess and usage problems the engine had before.

Here's a video of a single lap from session 3, will have the whole session video posted soon with a better update.

https://youtu.be/GdXBultZxaY

[dontlifttoshift]

Don't drink that.

Seriously though, that's awesome! I'm glad it worked out just the way you had hoped.