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I noticed that too. Everyone seems confused on it.
You want to PULL blow-by out of the valve covers. A vented catch can will not do this, rather just direct the pressure [blow-by] to the can and filter the air before it's released to the atmosphere.
From a member on a DSM forum:
During cruise (15-20% throttle) at highway speeds I saw a low of only -.6in/hg while the map was reading -5in/hg to -9in/hg
At 5psi, 23% throttle at the highway speeds the lowest I saw was -1.1in/hg.
At idle it's equal atmospheric pressure.
At WOT, 23-24psi of boost, I usually see a low of -5in/hg to -6in/hg.
40% throttle, highway speeds, 15psi of boost I see around -3in/hg to -4in/hg
I am not a fan of the setup where one valve cover is vented and the other is attached to the intake pipe for a vacuum source. If the pressure in your valve covers exceeds the values above, guess where the blow-by is going.
Also, when it comes to using a check valve, nearly all that I played with are not sensitive enough to switch over at such low amounts of vacuum. If your check valve isn't doing it's thing until, say, -2in/hg, you just created a problem for yourself.
The best setup IMO is to have a functioning PCV _and_ a vacuum line from the intake pipe, both attached to a simple, sealed catch can, which is attached to both valve covers. This will give the can vacuum at nearly all aspects of operation.
And just to stir the pot, I have NO idea why people are bothering with the -AN fittings and hose. Other than looking cool there is no reason for it. Heck, the overflow for the coolant system I would argue is more important and warrants those fittings and lines more-so, yet I don't see a trend on that. It's a huge waste of money really.
The best setup IMO is to have a functioning PCV _and_ a vacuum line from the intake pipe, both attached to a simple, sealed catch can, which is attached to both valve covers. This will give the can vacuum at nearly all aspects of operation.
I would not recommend this. You will apply max vacuum to your crankcase. What ever your engine vacuum is it will be the same in the crankcase.
Originally Posted by beaner
And just to stir the pot, I have NO idea why people are bothering with the -AN fittings and hose. Other than looking cool there is no reason for it. Heck, the overflow for the coolant system I would argue is more important and warrants those fittings and lines more-so, yet I don't see a trend on that. It's a huge waste of money really.
Simple they look good..
Just like a hi rise intake,
billet valve covers etc.
. they aren't needed but they look good.
What do you mean? A PCV valve from the valve cover to the intake manifold is common practice - at least from what I've seen.
A DSM for example has 2 barbs off the valve cover. One going direct to the intake manifold with a PCV valve inline, the other having a line go direct to the intake pipe.
What do you mean? A PCV valve from the valve cover to the intake manifold is common practice - at least from what I've seen.
A DSM for example has 2 barbs off the valve cover. One going direct to the intake manifold with a PCV valve inline, the other having a line go direct to the intake pipe.
you said
I took this as you describing pcv with no breather so no fresh air coming in.
Originally Posted by beaner
The best setup IMO is to have a functioning PCV _and_ a vacuum line from the intake pipe, both attached to a simple, sealed catch can, which is attached to both valve covers. This will give the can vacuum at nearly all aspects of operation.
Originally Posted by beaner
Yeah, that's the idea. That's also how it is stock on many vehicles with the exception of an inline can.
I'm open to all information, if my set up doesn't work and or ingest oil through the intake then I'll change the set up. I was simply inquiring because it seems LS guys all run a small can vented to the atmosphere. I posted the question on here for discussion not butt hurt. David Lampe shared his setup with me on his boosted vette which is closed loop routed back to intake and his boosted truck which uses a larger vent to atmosphere setup, both not ingesting any oil and making some damn good power.
01-12-2017, 06:03 PM
