Pro's / Cons - Oil Cap Breather.... ?
Thread Starter
Tech Contributor
Joined: Jan 2004
Posts: 20,030
Likes: 289
From: Wylie TX --> Less is More, except under the hood !
Pro's / Cons - Oil Cap Breather.... ?
Guys:
Right now I have my valve cover breather line going into my red intake.... See below pics #1, #2 , #3 ....
When I installed my Fast 92 with a LS2 TB ...., the LS2 TB did not have a port to plug in the breather line (LS1/LS6 TB does have a port)
I had to cut a hole in my red intake to plug this line in.
It is epoxied in the red intake well, and its holding for now.
I was wondering if anyone has one of those Oil Cap Breathers ? (See 4th pic below)
What are the Pro's and Con's of using the oil cap breather ?
- Oil mist on engine over time ?
- Not legal ?
- Best one to get ? Any one better than another ?
- I want one that "blends" in with everything else.
If I install one of these I plan to remove the red coupler with the hole and install a new red coupler with no hole.
Thanks for your input !
Toque
Right now I have my valve cover breather line going into my red intake.... See below pics #1, #2 , #3 ....
When I installed my Fast 92 with a LS2 TB ...., the LS2 TB did not have a port to plug in the breather line (LS1/LS6 TB does have a port)
I had to cut a hole in my red intake to plug this line in.
It is epoxied in the red intake well, and its holding for now.
I was wondering if anyone has one of those Oil Cap Breathers ? (See 4th pic below)
What are the Pro's and Con's of using the oil cap breather ?
- Oil mist on engine over time ?
- Not legal ?
- Best one to get ? Any one better than another ?
- I want one that "blends" in with everything else.
If I install one of these I plan to remove the red coupler with the hole and install a new red coupler with no hole.
Thanks for your input !
Toque
Safety Car
Joined: Dec 2009
Posts: 3,724
Likes: 9
So you are planning on providing the "fresh air" side of the PCV with a breather?
Gambler, size 3 to website
Pfadt Race Engineering
888-972-2464
info@pfadtracing.com
Gambler, size 3 to website
Pfadt Race Engineering
888-972-2464
info@pfadtracing.com
Thread Starter
Tech Contributor
Joined: Jan 2004
Posts: 20,030
Likes: 289
From: Wylie TX --> Less is More, except under the hood !
But without a valve cover breather on the setup I have now, I need something to breathe.
A friend of mine got a full heads cam setup recently and the tuner installed a oil cap breather and did not run the line to the red coupler like I did.
Toque
Thread Starter
Tech Contributor
Joined: Jan 2004
Posts: 20,030
Likes: 289
From: Wylie TX --> Less is More, except under the hood !
Safety Car
Joined: May 2007
Posts: 4,812
Likes: 46
From: Taylorsville North Carolina
All that line from the tb to the valve cover does is provide air for the oil to flow out of top of heads, so it doesn't glub glub (like pouring oil quickly out of a quart jug). The fi crowd and the stroked crowd try to stay away from this line because the excess crankcase pressure or blow by can cause oil to cycle back through the tb and intake and make a mess. Plugging the valve cover tube and installing an oil cap breather will provide the air needed. Or just installing a breather on the tube will work. Unless you car has a lot of pressure or blow by, you should not see much of a mess. Take note though, the valve cover port does have a shield to keep the rocker arms from throwing oil out the tube - the oil filler does not. Frequent high rpms could cause the breather on the oil cap to soil your motor. Good luck with which either way you go.
Thread Starter
Tech Contributor
Joined: Jan 2004
Posts: 20,030
Likes: 289
From: Wylie TX --> Less is More, except under the hood !
All that line from the tb to the valve cover does is provide air for the oil to flow out of top of heads, so it doesn't glub glub (like pouring oil quickly out of a quart jug). The fi crowd and the stroked crowd try to stay away from this line because the excess crankcase pressure or blow by can cause oil to cycle back through the tb and intake and make a mess. Plugging the valve cover tube and installing an oil cap breather will provide the air needed. Or just installing a breather on the tube will work. Unless you car has a lot of pressure or blow by, you should not see much of a mess. Take note though, the valve cover port does have a shield to keep the rocker arms from throwing oil out the tube - the oil filler does not. Frequent high rpms could cause the breather on the oil cap to soil your motor. Good luck with which either way you go.
Can you give me more detail on what you mean above in bold ?
Toque
Burning Brakes
Joined: Jan 2013
Posts: 1,091
Likes: 1
From: Hercules CA
i think what he's trying to say is that, with the current valve cover breather system (factory) it shields the oil from spilling during WOT runs. and since your planning to put a breather through the oil filler, the filler does NOT have the system to block out oil during spirited runs possibly causing oil to go up through the breather and making a mess
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
5 Best & 5 Worst Corvette Daily Drivers
Joe Kucinski
The Headlights of Every Corvette Generation Explained
Joe Kucinski
5 Best & 5 Most Overrated Corvette Track Packages of All Time!
Joe Kucinski
Every 2027 Corvette Engine Explained
Joe Kucinski
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Verdad Gallardo
10 Ugly Corvettes That We Still Kinda Love
Joe Kucinski
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
Safety Car
Joined: May 2007
Posts: 4,812
Likes: 46
From: Taylorsville North Carolina
If you take your valve cover off and look under it, where the tube port is underneath, there is a plastic type shield that blocks the oil from being thrown out of it. Take off your oil cap and look in, and you can see a rocker arm. If motor has a lot of crankcase pressure, it can still force it out the tube, but it won't sling it out thru the tube. HTH.
Thread Starter
Tech Contributor
Joined: Jan 2004
Posts: 20,030
Likes: 289
From: Wylie TX --> Less is More, except under the hood !
i think what he's trying to say is that, with the current valve cover breather system (factory) it shields the oil from spilling during WOT runs. and since your planning to put a breather through the oil filler, the filler does NOT have the system to block out oil during spirited runs possibly causing oil to go up through the breather and making a mess
If you take your valve cover off and look under it, where the tube port is underneath, there is a plastic type shield that blocks the oil from being thrown out of it. Take off your oil cap and look in, and you can see a rocker arm. If motor has a lot of crankcase pressure, it can still force it out the tube, but it won't sling it out thru the tube. HTH.
Thanks guys ! That makes sense.
So is that why in my searches I'm seeing some of the more expensive ones with a metal shield at the bottom like this one below ?
Maybe its design is to resist the splashing of oil up into the filter ?
Toque
Thread Starter
Tech Contributor
Joined: Jan 2004
Posts: 20,030
Likes: 289
From: Wylie TX --> Less is More, except under the hood !
This one looks interesting.....
http://www.c-f-m.com/performancepart...m#.UtWrU_teGVg
UTMYg~~60_3.JPG)
VRBS!+)tw-!!~~60_3.JPG)
0E9s37FbYKBSBUj6zU4!~~60_57.JPG)
http://www.c-f-m.com/performancepart...m#.UtWrU_teGVg
CFM Performance now makes it easy to vent the crankcase on your Chevy LS series engine with our new billet valve cover breather kit. This kit is a direct replacement for your factory oil fill cap and allows unwanted crankcase pressure to exit.
This breather is the ONLY one in the market which incorporates a check ball to keep unmetered air from coming through while the crankcase is under vacuum. In other words, this breather acts just like a factory oil cap under normal driving conditions and when you get into boost it will release any crankcase pressure present.
This kit also has an integrated baffle to help contain any oil particles present in the engine rather than saturating the filter element and eventually leaking through like many other kits in the market.
The filter element is washable and has a chrome top for great looks. The pre-oiled cotton fiber traps dirt particles without restricting air flow.
This breather is the ONLY one in the market which incorporates a check ball to keep unmetered air from coming through while the crankcase is under vacuum. In other words, this breather acts just like a factory oil cap under normal driving conditions and when you get into boost it will release any crankcase pressure present.
This kit also has an integrated baffle to help contain any oil particles present in the engine rather than saturating the filter element and eventually leaking through like many other kits in the market.
The filter element is washable and has a chrome top for great looks. The pre-oiled cotton fiber traps dirt particles without restricting air flow.
Burning Brakes
Joined: Jan 2013
Posts: 1,091
Likes: 1
From: Hercules CA
Melting Slicks
Joined: Jan 2004
Posts: 3,138
Likes: 37
From: Burbank. CA.
Don't install the Oil Cap Breather. I had one for a brief time. High rpm's and left hand turns with high g-force will cause oil to come out the breather and all over your header. If it doesn't catch fire, you got luckey.
Steve
Steve
Racer
Joined: Aug 2005
Posts: 465
Likes: 16
On my 383 I left the PVC system in place and installed a low pressure adjustable pop-off valve in the oil fill cap. If the system is under pressure instead of vacuum, the pop-off valve releases the pressure. Doesn't look pretty but works fine & I think the pop-off was less than $5 delivered.
Thread Starter
Tech Contributor
Joined: Jan 2004
Posts: 20,030
Likes: 289
From: Wylie TX --> Less is More, except under the hood !
Thanks for the input's so far guys ! 
Steve:
I see exactly what your saying, and that is NOT a good thing !
Did you have one of the generic types though, or the well thought out one I posted in Post #11. Seems they put some thought into that one about the exact issue you speak of.
Thanks !
Toque
I see exactly what your saying, and that is NOT a good thing !
Did you have one of the generic types though, or the well thought out one I posted in Post #11. Seems they put some thought into that one about the exact issue you speak of.
Thanks !
Toque
Melting Slicks
Joined: Jan 2004
Posts: 3,138
Likes: 37
From: Burbank. CA.
Thanks for the input's so far guys !
Steve:
I see exactly what your saying, and that is NOT a good thing !
Did you have one of the generic types though, or the well thought out one I posted in Post #11. Seems they put some thought into that one about the exact issue you speak of.
Thanks !
Toque
Steve:
I see exactly what your saying, and that is NOT a good thing !
Did you have one of the generic types though, or the well thought out one I posted in Post #11. Seems they put some thought into that one about the exact issue you speak of.
Thanks !
Toque
Not sure what your doing, but I put a catch can in line. It will fill up in just a few laps of Autocross.
Steve
Safety Car
Joined: May 2007
Posts: 4,812
Likes: 46
From: Taylorsville North Carolina
The chrome one is a nice looking piece. However, if you remove the line from the tb to the valve port, then the one with the check valve will not work. Remember the purpose of that line is to help drain the oil out of the heads without the glub glub effect(and yes, glub is a word).
If you are not having issues with crankcase pressure, then your current system is fine. An oil cap breather would still get that unsightly hose out of the engine bay.
If you are not having issues with crankcase pressure, then your current system is fine. An oil cap breather would still get that unsightly hose out of the engine bay.
Acct Suspended APR 2026 by request
Joined: Dec 2010
Posts: 10,367
Likes: 1,272
2020 Corvette of the Year Finalist (performance mods)
C5 of Year Winner (performance mods) 2019
I had a -10an bung welded onto both of my valve covers and ran those to a jegs dual inlet breather can... I removed my pcv valve and capped off all the ports on my valley cover, intake, and throttle body... I still use the passenger valve cover fitting and that is ran to the inlet of my supercharger... since you are n/a I would assume you would cap that one off as well if you decided to go the breather can route... here is a link to the one I used, http://www.jegs.com/i/JEGS+Performan...52202/10002/-1 ... I also had to buy an extra -10an union to put in the other side of the can as it comes from jegs with a plug in one side... this might be overkill for your setup but I just wanted to give another alternative than using one of those breather oil caps... I wanted something that would allow my motor to breathe sufficiently under boost and eliminate oil in the intake... the only negatives I can think of would be condensation settling on top of the oil since it isn't being evacuated by the pcv but most of that will boil off when your oil temps get up to 190° or so and if you change your oil religiously like me then I don't see that becoming an issue