Catch Can - Motion Raceworks

[GCguy2169]

So I ordered a new catch can from Motion Raceworks. I want to make sure I set it up right, so I called them. I’m NA btw.

So.. one of the gentlemen there told me to cap off the valley cover crankcase vent and hook the can up to both valve covers. So the catch can has two ports and yes, I can easily do that.

What I’m not educated on is why? If I block off the valley crank vent, won’t the lower portion of the engine build pressure below the pistons? If I cap it off that is. Just seems to me that capping the bottom end, and opening the top end allows the bottom end to build pressure which can obviously be bad. Thanks all.

[Badbubba]

For the dirty side, catch can connects between the valley cover and intake manifold, behind the tb. Remove the short oem jumper hose. Just need to know the in and out on your catch can.

[GCguy2169]

Originally Posted by Badbubba

For the dirty side, catch can connects between the valley cover and intake manifold, behind the tb. Remove the short oem jumper hose. Just need to know the in and out on your catch can.

Right. I get all that. But per my post, I was concerned about crankcase pressure. Just was curious why Motion Raceworks would want the valley capped off and just to vent the valve covers.

[1LE_ROLL]

Motion thinks in a drag racing mindset, and the recirculating system is just an extra load of shit to please the EPA. Vent it to atmosphere. The reason to vent both valve covers instead of the valley and one valve cover is so you don’t get left with a bunch of pressure built up on one side. And it works fine trust me.

[Badbubba]

Originally Posted by GCguy2169

Right. I get all that. But per my post, I was concerned about crankcase pressure. Just was curious why Motion Raceworks would want the valley capped off and just to vent the valve covers.

I'm stating how it needs connected. Connecting at the valley cover is basically the same as connecting at the valve or valve covers. Shares the same "air" space. Except on the LS3, the driver's side valve cover would need to be drilled. And the passenger side valve cover has the port for the "fresh" metered air and would need to be drilled. But then your PVC system wouldn't function very well. Because you'd be supplying air to the passenger side valve cover, the sucking it away to the catchcan. You would not be evacuating the crankcase's contaminated vapors. What's your concern with crankcase pressure? Are you concerned that the catchcan is restrictive and will therefore build crankcase pressure? It's not. Or is it the idea of capping off the valley cover? If so, there is no separation between the upper and lower part of the engine, air circulates through it all. Besides if there is excessive crankcase pressure, it will vent through the clean side, reversion. The hard line that's attached to the intake tube. That's why people put a catchcan on the clean, "supply", side. You stated you have a 2 port can, you would need to use a tee to connect the 2 valve covers or have a 3 port catchcan.

[1LE_ROLL]

Originally Posted by Badbubba

I'm stating how it needs connected. Connecting at the valley cover is basically the same as connecting at the valve or valve covers. Shares the same "air" space. Except on the LS3, the driver's side valve cover would need to be drilled. And the passenger side valve cover has the port for the "fresh" metered air and would need to be drilled. But then your PVC system wouldn't function very well. Because you'd be supplying air to the passenger side valve cover, the sucking it away to the catchcan. You would not be evacuating the crankcase's contaminated vapors. What's your concern with crankcase pressure? Are you concerned that the catchcan is restrictive and will therefore build crankcase pressure? It's not. Or is it the idea of capping off the valley cover? If so, there is no separation between the upper and lower part of the engine, air circulates through it all. Besides if there is excessive crankcase pressure, it will vent through the clean side, reversion. The hard line that's attached to the intake tube. That's why people put a catchcan on the clean, "supply", side. You stated you have a 2 port can, you would need to use a tee to connect the 2 valve covers or have a 3 port catchcan.

You wrong. Motion is a 2 in with a breather for the out. So you cap the return on the intake. And super weird my LS3 didn’t need the valve cover drilled at all... just had a rubber cap from
Factory. Some catch cans don’t recirculate like you are saying. Motion race works being one of them.

[Car Nation Videos]

If I were you, I would call Motion Race Works and ask why they are recommending it.

[Badbubba]

Originally Posted by 1LE_ROLL

You wrong. Motion is a 2 in with a breather for the out. So you cap the return on the intake. And super weird my LS3 didn’t need the valve cover drilled at all... just had a rubber cap from
Factory. Some catch cans don’t recirculate like you are saying. Motion race works being one of them.

Maybe op should have stated the design or a picture of the catchcan. As I'm not going to research models and manufacturers. When I stated how it should be connected in my 1st post, there was no reply about the style of the can. I figured it was a standard catchcan since Motion Race Works didn't state to the op to also cap off the dirty side at the intake manifold, behind the throttle body. That would create a vacuum leak, by only capping the valley cover. And may as well remove and cap the clean side, as it will serve no purpose. Since there is no vacuum pulling the contaminated air from the crankcase, no need to supply air. The L99 uses the driver's side valve cover. So it would make sense for GM to standardize covers and use plugs.

[Cyber10]

I'm assuming it's this can?

[Badbubba]

Originally Posted by Cyber10

I'm assuming it's this can?

Thinking it's a different one. Not sure if it's the same catch can but the other Motion video states to connect to each valve cover and block off the valley port. Ended up researching Motion somewhat. And then in the comments, someone asked about the port at the intake manifold. Motion's reply was to cap it. Surely they would have a different catchcan for each application. ???? I would prefer the can between the valley cover and intake. But, unless the breather has a check valve, the catchcan and crankcase evacuation would be of no value. And suck unmetered air.

[1LE_ROLL]

I have a motion catch can bubba chill out lol he’s asking people who know... you are giving wrong information by continuing to tell him to put it on the dirty side. It’s not a one way flow catch can. And yes motion only makes one type of catch can....

[Moto-Mojo]

I got chastised for being anal about torque ratings on a brake caliper bolt. This is just a catch can.

[Cyber10]

Originally Posted by 1LE_ROLL

I have a motion catch can bubba chill out lol he’s asking people who know... you are giving wrong information by continuing to tell him to put it on the dirty side. It’s not a one way flow catch can. And yes motion only makes one type of catch can....

I misread their website, I thought it mentioned this being an improved design on a previous version but I think they were maybe just referencing improving traditional catch can designs that they've used before.

[Badbubba]

Originally Posted by 1LE_ROLL

You wrong. Motion is a 2 in with a breather for the out. So you cap the return on the intake. And super weird my LS3 didn’t need the valve cover drilled at all... just had a rubber cap from
Factory. Some catch cans don’t recirculate like you are saying. Motion race works being one of them.

Originally Posted by 1LE_ROLL

I have a motion catch can bubba chill out lol he’s asking people who know... you are giving wrong information by continuing to tell him to put it on the dirty side. It’s not a one way flow catch can. And yes motion only makes one type of catch can....

1st off, don't tell me "you wrong". I'm inquiring about what the op has and about their fundamental concern. 2nd, drop the attitude with with telling me to "chill out". You've got 28 posts, so learn how to be civil. I had a generalized statement about where I would prefer the can, I did not state the Motion can. I even commented about them possibly making 2 cans. And in my 1st post about which fitting was in and out. Why? Because a can that exits into the intake manifold needs to have directional flow to achieve the best possible results. I will say it again, I prefer A CAN between the valley cover or valve cover and the intake. If the op was not experiencing high crankcase pressure, being NA, then why modify the pcv system to vent to the atmosphere? Doing so eliminates the evacuation of the crankcase's contaminated vapors. Which would most likely lead to more frequent oil changes or other issues.