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I am running Holley LS high-height valve covers on my LS3. My valley cover does not have a vent on it but looking for the best way to ensure I can properly vent. Is it best to just use those vent nipples on each valve cover and run them to a catch can? Anyone have any images of their setup? What did you do with your throttle body line? Another catch can with a filter on top?
Last edited by SupaDoopa; Oct 22, 2021 at 01:40 PM.
10AN lines from each valve cover to a breather can and a 3/8" line off the valley cover to a small breather tucked away in the passenger fender. Cap off the intake and throttle body ports.
[QUOTE=01CamaroSSTx;20388154]10AN lines from each valve cover to a breather can and a 3/8" line off the valley cover to a small breather tucked away in the passenger fender. Cap off the intake and throttle body ports.[/QUOTE]
As stated, my valley cover doesn't have a port. I'm mainly asking if it's acceptable to just have the two valve covers vent to a breather can and call it a day.
With -10 or -12 lines to a breather can and another breather for the oil fill cap you'll be fine. Don't think 6AN lines are adequate for venting but if your plans are to keep PCV by use of the intake port you could leave the 3/8 lines as is and run a sealed catch can. Drive side would go through the can and into the intake manifold while the passenger side would connect to the throttle body or run into another sealed catch can and then to the throttle body.
With -10 or -12 lines to a breather can and another breather for the oil fill cap you'll be fine. Don't think 6AN lines are adequate for venting but if your plans are to keep PCV by use of the intake port you could leave the 3/8 lines as is and run a sealed catch can. Drive side would go through the can and into the intake manifold while the passenger side would connect to the throttle body or run into another sealed catch can and then to the throttle body.
I'm not really intent on keeping it any specific way. I'm just looking for the best method. The available ports I have are 1 on each valve cover, 1 on the throttle body, and 1 on the intake manifold. So essentially, I'm just looking for the best way to route it all. This is a fresh build so I don't have any of the OEM items at my disposal.
Remember on any PCV you need either the PCV valve or a restrictor like GM does with a .100 hole. Here is a photo of the valley tube you have on the LS motor - you can see restrictor in there. If you do not run this the manifold air intake will suck to much in and you will get a lot of oil in manifold. If you are just running breather to atmosphere that is fine. But the PCV system need some restriction or it becomes a big oil sucking vacuum leak.
Your valve covers do not have this provision either so if you're planning on running PCV you'll need to get an inline PCV valve and route the lines as in post#4 to a sealed can then out of the can through the inline valve then into the intake manifold. Which way is better? That depends on its intended use and what it is your doing but in order to be emissions compliant you need to run PCV and if the vehicle inspector notices that it's not then he could fail you.
I have tried all sorts of different crankcase venting options. What I have works really well. Your vent tube may work ok, but you need an actual breather on one side of the motor and and vent to pull from on the other. You will need a Mishimoto baffled catch can. I actually have a 1/2" vent with a breather on the other side with a Mishimoto and a McNally can in series together. I have a supercharger on a stroker motor so I have a lot of crankcase pressure, but I have found this to be the best option for me short of a vacuum pump.
You may only need the the mishimoto can on yours. The good thing is these cans have a drain option on the bottom. My Supercharged 2013 Camaro with RHS block, AFR heads, &......
The reason I ask is I have 4 open nipples on the engine: 1 on each valve cover, one on the throttle body, and one on the intake manifold. My main question is what is the best way to ensure I can vent some pressure while also keeping oil out of the intake setup. Maybe a crappy MSPaint diagram is a smart play?
Cap off the intake and throttle body ports and connect a hose to a breather on the driver side and another one to the passenger side. I don't believe that either of your valve covers has the orifice as shown in post 6 and I'm not sure what the baffle's look like but feel those should be adequate for venting the crankcase. I would prefer larger openings in the valve covers such as 10AN fittings and larger 10AN lines to dual breather cans but a single breather can has been getting it done on my LSX427. It was just recently that I added a 3/8" line and small breather to the valley cover port which you do not have but you could replace the oil fill cap with a breather style cap and that will give you another place to ventilate the crankcase.
Last edited by 01CamaroSSTx; Oct 26, 2021 at 04:40 PM.
Cap off the intake and throttle body ports and connect a hose to a breather on the driver side and another one to the passenger side. I don't believe that either of your valve covers has the orifice as shown in post 6 and I'm not sure what the baffle's look like but feel those should be adequate for venting the crankcase. I would prefer larger openings in the valve covers such as 10AN fittings and larger 10AN lines to dual breather cans but a single breather can has been getting it done on my LSX427. It was just recently that I added a 3/8" line and small breather to the valley cover port which you do not have but you could replace the oil fill cap with a breather style cap and that will give you another place to ventilate the crankcase.
Those are the exact covers on my LS3 right now. I actually was looking at Radium's oil cap that has the ability to have an AN line/hose connected to it. However, that would give me only one other 'hose' for lack of better term. Do I just weld on another fitting to a standard can and vent all 3 to the same place with small screw-on style air filter on top to relieve the pressure atmospherically?
So you don't have the valve covers where the passenger side has an oil fill cap? If this is correct then you obviously have dry sump and your adding oil elsewhere but I would think you could get away with running hoses from the valve covers to a breather can and cap off the intake manifold and throttle body ports, and again if it were possible to open those holes up on the valve covers to a larger size in order to weld 10AN or 12AN bungs onto them you could then run larger lines which will expand the capacity of the lines and aid in the ventilation of the crankcase.
Remember: If you're going to ventilate to atmosphere then make sure your lines are large enough to relive the pressure in the crankcase but if you decide to keep PCV and you want to connect everything up correctly you would run a 3/8 rubber hose from the driver side around the back of the engine and along the passenger side of the intake manifold and just before you connect the line to the manifold port you would install an inline PCV valve. For the passenger side valve cover you connect it to the throttle body port and then you will have what is known as positive crankcase ventilation. You could also install a sealed catch can between the driver side valve cover and the intake manifold with an inline PCV valve in between the can and the port on the manifold but not a breather can because by doing this you will be pulling in unmetered air into the intake manifold.
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Manifold breather catch can? 
