LSX 454 PCV Catch can / Oil breather

[49.5window]

I have a LSX 454 with a carburetor and I want to add a catch can to the pcv system. The instructions with the motor say the following.
There are 3 ports on the lsx engine the make up the pcv system. There are 2 foul side ports and both of theses ports should be connected to the intake manifold and be exposed to vacuum at idle.
The 2 ports are) front port on the valley cover) left rear driver valve cover. These two silver tubes may look simple but, they should not be modified. Both tubes have a small orifice within them that, is used in place of a PCV valve of early designs.
There is one fresh air port which is on the front of the right passenger valve cover. This port should be connected to the filter clean air (air cleaner).
My question is what line do I use for inlet of the catch can and what line connects to the outlet port on the catch can? How do I plumb this so it all works as stated above?
Thanks,
Gary

67604

[sjaroslo]

Hi, Gary:

I don't exactly have the answers for you, but I did just want to chime in to let you know that Chevrolet Performance has a newer document available for the LS Crate Engine Control System, and they've changed several items from the copy that I'll bet that you have; I have the same engine in my build and I have the same questions as you (I'm just not there in my build yet). Some of the changes are not too substantial, and some are--I would recommend keeping both docs available. Here's what the new doc says about PCV:

"Positive Crankcase Ventilation System (PCV)
How to set up your PCV system:
There are two ports on the engine that make up the PCV system. The
ports on the engine are:
1) Left rear (driver side) valve cover.
2) Top center of the inlet manifold.
The ports with silver tubes may look simple but, they should not be
modified. The tubes have a small orifice within them that is used in
place of a PCV valve of earlier designs.
There is one fresh air port which is on the front of the right (passenger
side) valve cover. Again this is a silver tube that faces forward on the
valve cover. This port should be connected to filtered clean air. This
connection must be within the engines air cleaner system and must be
between the MAF (Mass Air Flow Sensor) and engine’s throttle body.
The engine burns the air that enters the PCV system so, if the fresh air
port is prior to the MAF then, this air will enter the engine without being
measured by the MAF and adverse engine operation may occur."

And:

"How the PCV System Works:
A closed crankcase ventilation system must be used in order to provide
a more complete scavenging of crankcase vapors. Filtered air from
the air induction system (air cleaner) duct is supplied to the crankcase,
mixed with blow-by vapors, and passes through a crankcase ventilation
metering device before entering the intake manifold. The primary
component in the positive crankcase ventilation (PCV) system is the
PCV flow metering orifice. Vacuum changes within the intake manifold
result in flow variations of the blow-by vapors. If abnormal operating
conditions occur, the design of the PCV system permits excessive
amounts of blow-by vapors to back flow through the crankcase vent
tube and into the engine induction system (air cleaner) to be consumed
during normal combustion. This engine ventilation system design
minimizes oil consumption and significantly reduces the potential for oil
ingestion during vehicle limit handling maneuvers."

(sorry, also just realized that, with you going with a carb, not a lot of that is going to apply to you; I'm going FI).

Maybe Mike Norris will chime in on this thread. I'm subscribed! Let me know if you can't find the link.

[parsonsj]

Gary,

You want a Norris catch can between the two "foul side" ports and engine vacuum. I'd get 3 catch cans, and use one on each of the foul ports, and one on the clean side.

Air flows from the clean side to the foul side, so your foul ports connect to the inlet side of the catch can and the outlet of the catch can goes to engine vacuum.

You will also want a catch can on the clean side, since at WOT you'll push crankcase vapor (foul air) out of the clean side since vacuum drops to zero. On the clean side you want the connect the catch can inlet to the passenger port, and the outlet side of the catch can to clean air (usually your air filter, or your MAF tube).

Hope that helps.

[49.5window]

John,
Could I also fabricate a catch can that has 3 -10AN inlet/outlet ports on it like a 5" x 5" x 5" with a aluminum mesh filter so I can use 1 catch can? I'm a machinist and welder so I can make my own out of billet aluminum.
Thanks for your help.
Gary

[parsonsj]

Gary ... maybe. You need to keep the clean and foul sides separate so that clean filtered air flows into the passenger side valve cover, and the dirty air flows out and into the intake manifold. One big reservoir with multiple fittings won't work.

Another thing is that Norris' stuff works. It's been tested and is in use on thousands of vehicles. You might be able to make something that works, or not. And you can spend a lot of time and money trying to save a buck.

jp

[49.5window]

Good point, I'll stick to 3 Norris separate catch cans.
Thanks for all your help.
Gary

[sjaroslo]

I'm not arguing that this isn't the optimal way to go, but I'm just wondering how practical this approach really is.... I think Mike's cans are like 13" tall? Just figuring out where to mount them such that they don't dominate your engine bay with their presence and plumbing seems like the first challenge.... Couldn't you at least plumb the two foul side ports to 1 can? And how does the OEM get around it, considering this is a relatively "stock" configuration? Also, when you factor in an overflow can for the cooling system, that's a lot of hardware and plumbing to try to accommodate in an engine bay that many are trying to keep looking as aesthetically pleasing as possible.... I'm not trying to put form over function but I just don't see this approach as practical. For me, realistically, I'm going to spend very little time at WOT, so putting a can on the clean side seems like total overkill, and I can't see putting dual cans on the foul ports unless plumbing them together somehow overrides a built-in function of keeping them separate. Again, not trying to be argumentative and I certainly don't know anything about the topic, just trying to come at it from a practical perspective for a street-driven machine. Thanks for listening.

[parsonsj]

The factory doesn't use catch cans, because most people don't care that the inside of their intake manifold and air cleaner gets coated in oil. Their directions are pretty clear: hook the the foul side to engine vacuum, and the clean side to the air cleaner.

Done.

If you want a simple engine bay, that's the way to do it.

Could you combine the two catch cans on the foul side? Sure. Would that compromise something GM knows about the the need for two separate paths to engine vacuum? Probably, but maybe not. Could you run one for the two foul ports, and connect the clean side directly to the air cleaner. Sure. There are lots of ways to connect this, and there are compromises to make no matter what you do.

On my hot rod, with that engine, I'd use three catch cans. On my LS7 Z06, I use two, because there is only one foul port. I run one for the foul side, and one for the clean side. My engine spends a lot of time at WOT, and oil does accumulate on the clean side. I have to empty them after every event.

Lots of ways to do all this, and there's no perfect answer that is optimal for every parameter.

Hope that helps.

[MrQuick]

Hi John, would you have to connect the 3 cans?

I bet a competent machinist and weldor could make a larger capacity can with internal baffles and a breather cap. Maybe have a top port feeding a traditional PCV valve to the 3/8" port at the base of the carb.

[parsonsj]

Hey Vince, I think a competent machinist and welder could make something too. But will it work? Maybe -- maybe not. Mike gets $130 per catch can. The question is if you want to iterate through some design changes and testing, or just buy something that works. It's easy to spend a lot of time and money saving a buck.

You mention a "breather cap". There's no breather cap in a proper PCV system. Just sayin' ... :)

[49.5window]

John,
Does it matter about the height of the catch cans compared to the engine ports? Can the cans be lower than the engine ports? Also what type and brand hose did you use on your engine and are you happy with it?

[parsonsj]

Putting the cans low is a good thing. You want them to trap oil, and gravity is your friend in this situation. For oil, nearly any quality hose will work fine, but it needs to be vacuum-rated. I've found Earl's Pro-Lite 350 works well, and that's what is on my Z06.

[sjaroslo]

John, I hope that Norris is giving you a spiff of some variety! It must pain you to tell people to mount something LOW and to use pretty much any old hose.... Seems like it is unholy to all that is II Much Fabrication's Fuel Vent!

[parsonsj]

Steve, lol!

Yes, Norris' catch can and the II Much Fuel Vent have the exact opposite requirements it seems.

I think Mike owes me lunch. :)

[MrQuick]

Hey Vince, I think a competent machinist and welder could make something too. But will it work? Maybe -- maybe not. Mike gets $130 per catch can. The question is if you want to iterate through some design changes and testing, or just buy something that works. It's easy to spend a lot of time and money saving a buck.

You mention a "breather cap". There's no breather cap in a proper PCV system. Just sayin' ... :)

If that were totally true neither of us would have jobs. : )
I wasn't bashing Mike's can. I like to see people make stuff from scratch. Hell, I built my business on a $4 home made part.
Sorry, when I said breather I meant fresh air intake system, hose, port, valve, oriphis, bladder, screen, filter, pathway or something rather like it.

[parsonsj]

Vince, I hear ya. One other thing is that GM factory ECMs (including their crate motor offerings) actually account for the foul air being burned through the PCV system. So the fresh air intake side of the system needs to be plumbed in the engine intake between the MAF sensor and throttle body. Plumbing the fresh air intake anywhere else will cause the engine to run lean since it's burning more air than is being measured by the ECM.

[49.5window]

John,
I only have 1 port on the passenger side of the intake at the rear for the foul air, is it ok to put a Y fitting there and run both foul side lines from the outlets of the foul side cans into this 1 port?
Thanks,
Gary

[parsonsj]

Gary, the instructions aren't very clear, are they? It would be awesome if we could get to somebody in GM Powertrain and get a definitive answer. Absent that, a Y-connection will probably be fine.

[vstol]

Gary and Steve, I would like to bend your ear about the LSX 454 since my 418 purchase fell through. My home email is [email protected]. I would greatly appreciate what you have to say about the motor since it has now made it into my list of options for my build. Thanks Kevin

[sjaroslo]

E-mail sent :)

[sjaroslo]

Dredging up an old thread to ask the question, now that I'm here in MY build--which port is which on the Norris catch can? The one on the side just opens in to the body of the can, and the one on top looks to have some kind of separator, etc attached to it. I'm just ignorant enough that I can make a compelling argument for either one doing either thing in my head.... I'm thinking that the side port on the can attaches to the foul ports on the engine and top port connects to the intake manifold (vacuum). Thoughts? Thank you.

[sjaroslo]

Just answered my own question by studying Mike's web page a little closer. Not sure how I missed this! "The port from the valley cover goes to the top of the catch can and the port on the intake goes to the side of the catch can." And once again my logic is bass ackwards!