Possible Solution for Valve Cover Breather Oil Leaks


Active Member
I did some maintenance this winter and was trying to find a oil leak that i have been chasing for a while now. I thought it was the valve covers, then the rear main seal, etc. My starter would have oil dripping down it and the oil drips would wind up directly in the center of the flywheel cover. Well, after much work here and there, and changing gaskets, etc. I found it was leaking from the my valve covers. I have the GN1 covers, with the push in style Metco Breathers, on the angled push in style adapters.

I thought about making a baffling solution in the valve cover, but found 1 or 2 small threads here mentioning gasket baffles.

I found some in the store and wanted to share them since the leaking valve covers is an ongoing topic on here and there are no good threads in here about them that "I" have personally found.

Mr. Gasket sells these:

Baffled Grommets - P/N 5425

They can be picked up from the local O'Reillys for like $3 for a set of 2.


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If you look at the picture you can see the baffling. In my line of work, we call it a "torturous path" OR step that doesn't let oil directly through. Now.....I did have to cut a small square window out, because there was no pass through. So intially it was just a "plug" with the potential to have a good pass through hole for air. I tried to show it in the pictures below.

The method I used for making the rectangle air pass thru, was to use an exacto knife. I flipped the grommet upside down, and squeezed it tightly so that area I wanted to cut would expose itself. The exacto knife is long enough to get down into the hole. Then just cut it out carefully without cutting your fingers ;-)

The 1st picture shows how I squeezed it while cutting it. The rest of the pictures shows what path the oil will have to travel in order for it to get out, while still allow the air pass through. (Essentially keeping the crank from ventilated) You can see the daylight through the hole.


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I also found these from Summit Racing.

P/N SUM-G3428

This are sold individually for like $1.50 each.

I like that these have a piece of foam in them that will definitely stop any oil from bypassing the "stepped" path just in case.

These summit racing ones have a have a little pre-cut baffle door "flap" on them as you can see in the last picture (picture #6). I cut that out completely to allow more air flow once the foam is in place.

The foam is a bit restrictive so, I cut it in half with scissors and then installed it into the grommet.

So my total mods to this one was cutting the foam in half (1 of the half pieces of foam) and cutting the flap out.


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Here is a side comparison of the old "plug" style grommet vs the baffled one. It shows the difference in depth between the two.


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From what I noticed, the Summit Racing ones fit much better than the Mr. Gasket grommets. But both will work just fine once the aluminum adapter is installed.

What I mean by "fit better" is the Mr. Gasket ones spin a little too much once installed in the valve cover (without the adapter) and even once the adapter is installed, it can still spin. The Summit Racing one is more smug without the adapter installed (and tightens up a lot better with the adapter installed)

In conclusion, they fixed my problem. Cleaned the breathers and they are still dry. along with my starter and the fly wheel cover.

Hope this helps someone in the future.
Those are fine for putting around but the blow by gasses at wot will still need to escape. Usually carrying a mist of oil and fuel with them. The cross section on those grommets is inadequate to vent the crankcase at wot. Welding extensions into the valve covers with hose going to a can with a breather vent will prevent oil from leaking

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I always cut those baffles off to allow the crankcase to breath. The blow-by has to escape, especially at WOT. The baffles get in the way and introduce restriction to the breather, causing crankcase pressure to rise.
Hi bison,
I have a catch can Installed along with a new stock ac delco pcv and and rjc racing pcv ran inline with the stock pcv. I was still getting a pretty good amount oil blow by.

You have an example of the extensions attached to the valve cover that I can view?

I only installed this baffled grommet to the passenger side , my driver side isn't using a baffle. The driver side just has the angle Metco adapter with breather.

Do you think there still isn't enough ventilation?
Those are fine for putting around but the blow by gasses at wot will still need to escape. Usually carrying a mist of oil and fuel with them. The cross section on those grommets is inadequate to vent the crankcase at wot. Welding extensions into the valve covers with hose going to a can with a breather vent will prevent oil from leaking

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I am going to look in the option of getting a catch can with a breather. How should I run the lines if I got a catch can with a breather vent? Currently I am running a rjc check valve inline with stock pcv, and I have a catch.
I came home and measured the openings of the baffles. I also measured the angled adapters to figure out the cross-sectional area of the openings to find out what the difference really is. The baffle opening measured 0.225in. X 0.88in. Which equals to 0.198in^2. I was measuring the adapter, but then noticed that the opening of the adapter isn't what should be measured, the opening to the inlet into the metco breather should be. The adapter has a large port ID of 1.25in. , but the port/pathway is shrunk all the way down to a 0.5in hole (the hole in the breather). With that being said, the cross-sectional area of the metco adapter is 0.196in.^2. So the baffle actually has about the exact same opening as the breather. The foam adds a little more restriction, of course, but I did cut it down. If I remove it completely, the baffles should flow the exact same air flow as the breather without the baffles would.

Am I missing something? (Guys, I just want to say that I am not being a smart-ass or anything. Most of you guys have been working with these cars much much longer than me. I will take your advise by adding the vented breather if needed, but I want to make sure I competely understand before I go spend another +\- $110.)

Thanks in advance.
Those are some nice pieces T-type Tim. How will the hose routing go? I know that a hose will go from the v.c. breather to the catch can. But how does the routing go before that?

Currently, I have a hose coming from the stock pcv to the catch can catch, from the catch can to rjc check valve, to the vacuum block port.
thx for the heads up Nick

I have the PCV hooked up in stock configuration with a kirban valve ...the valve cover breather/vent system will be independent.

I'm not sure exactly where I will mount the breather, may mount it to radiator support or fire wall...I'd like to keep a minimum of line to reduce clutter.
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I may be missing something here, if you keep the pcv hooked up in the stock configuration with the kirban valve and keep the vent system independent by connecting the v.c breather to the catch can..... aren't u missing a connection some where? The catch can has an "in" & "out" port, so you are porting in but where will your "out" go?
Tim, be aware you will need to modify the valve covers at the least, and probably will need to weld on those breathers like I did on one of my cars.

Chris Hogeland made these for me

Which form part of a catch can system on my valve cover vents.

Probably overkill but I have no more oil out the breathers
Wow Tim, that looks very nice! Even though mine is not "modified " and I don't run her very hard, I just might do the same to mine. I just like the way it looks...