SBC leaking oil through the valve cover breather

[BrazilianZ28Camaro]

Hi fellow gearheads

I just did some 5500 RPM (half foot) tests with the new 421" to see how she's liking the jets and timing....so far the street tires proved to be useless at speeds lower than 60 mph.

But I noted the right hand valve cover breather did leak a bit of oil , I'm not sure why....I'm running 6 1/2 quarts with a 6 qt milodon oil pan with windage tray and 1 qt oil filter,so half qt lower than maximum level.

Oil is std 15-40. Oil pressure always good, 40 PSI at hot Idle, 60 PSI at 2000 rpm and above.

I was thinking to drain half quart more and test....I could plug the RH breather and let only the LH open. Engine didn't have a PCV valve or any kind of external vacuum source to the crankcase.

What do you friends think?

[F-BIRD'88]

valve cover breather baffling (lack of) oil control is alwayss a issue.

you need to get creative. Look at road race and nascar prepped cars for inspiration.

[Kevin Johnson]

What do you mean by right hand valve cover? From the perspective of facing the crank pulley in front of the car or sitting in the driver's seat behind the motor?

[rfoll]

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Most of the breathers I have seen have a sponge of paper to keep debris out. They quickly become saturated, and when the engine produces crankcase pressure, it pushes the oil out. I use the ones from Mr. Gasket with the tube projecting from the side of the enclosure. I remove the sponge from the inside and run a hose from the tube away from the motor. Nothing ever comes out of the hose, but before everything was always wet from the oil mist.

[Cubic_Cleveland]

valve cover breather baffling (lack of) oil control is alwayss a issue.

you need to get creative. Look at road race and nascar prepped cars for inspiration.

This is where I'd be looking. What kind of baffling (if any) is under the breather?

[ProPower engines]

Again baffling is the key. Most custom of aftermarket valve covers do not have any baffling in them and almost always there is a rocker under and inline with the opening so the push rod oil hole squirts oil directly at the opening in the cover.
The opening at the rear on the passenger side is even worse as the oil is trying to drain there and fills the rear of that area and can be forced out by some base pressure at higher RPM.

I weld a 3" long baffle inside the covers the fill holes and PCV holes to avoid any splash induced oil venting in these areas. Helps keep things clean on the outside

[robert1]

I just had to ad a baffle to my daughter's LS motor because there is a service bulletin about changing the cover. Even after all these years they still don't have this figured out. If it's only leaking out one side that's a very good sign. Should be able to do some type of mod to correct it.

[Kevin Johnson]

Hi fellow gearheads

I just did some 5500 RPM (half foot) tests with the new 421" to see how she's liking the jets and timing....so far the street tires proved to be useless at speeds lower than 60 mph.

But I noted the right hand valve cover breather did leak a bit of oil , I'm not sure why....I'm running 6 1/2 quarts with a 6 qt milodon oil pan with windage tray and 1 qt oil filter,so half qt lower than maximum level.

Oil is std 15-40. Oil pressure always good, 40 PSI at hot Idle, 60 PSI at 2000 rpm and above.

I was thinking to drain half quart more and test....I could plug the RH breather and let only the LH open. Engine didn't have a PCV valve or any kind of external vacuum source to the crankcase.

What do you friends think?

I looked at a picture of your engine (seen below) and am assuming that you mean the vent nearest to the firewall.

The valve covers appear to be polished and painted versions of the Chevrolet Performance 12480127 aluminum valve covers that already have baffles from GM.

You are running steel four-bolt main caps so I am assuming they are the aftermarket style that tends to block flow around the ends from bay to bay; the stock four-bolt main caps are rounded at the ends.

The oil pump body projects into this area and the clockwise windage flow collides with it and is further channeled/confined by the main caps. This creates a localized higher pressure zone as well as very fine droplets of oil from multiple impacts with the pump body. This mist is naturally driven up near the camshaft where the lobes are spinning opposite to the movement of the crankshaft and this directs the mist up into the valley. The closest path to vent to the atmosphere is back up the drain hole in the rear of the cylinder head directly underneath the valve cover vent. Mist traveling up the other head will have a longer path to travel and the droplets will be more likely to adhere to surfaces along the way.

If you add additional baffling to the factory part be careful that it does not have any chance of vibrating loose. Try blocking the vent if you don't want to risk damaging your valve covers or switch to an alternate style vent cover that provides a passage to a catch can (or draft tube as seen in a previous post).

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[F-BIRD'88]

From the picture: Just having the breather at the back of the motor is a issue in of itself.

Should be at the front of the motor, like the other side is.

Righteous job on this car thou.

[rfoll]

When I had this problem, baffling the valve covers did little to solve the problem. The breathers are for providing some kind of vent to atmosphere. If the baffle in the breather isn't mechanical, (like a chambered muffler), it will eventually become saturated, and it is going to end up on the motor. If my engine compartment looked as clean as yours, I would be looking for a solution too. If what I did didn't work, my next step was too find enough room on the firewall for a catch can.

[BrazilianZ28Camaro]

What do you mean by right hand valve cover? From the perspective of facing the crank pulley in front of the car or sitting in the driver's seat behind the motor?

Sorry, I should say passenger side valve cover.

[BrazilianZ28Camaro]

valve cover breather baffling (lack of) oil control is alwayss a issue.

you need to get creative. Look at road race and nascar prepped cars for inspiration.

This is where I'd be looking. What kind of baffling (if any) is under the breather?

The valve cover have a sheet under the hole about 3" wide, covering the direct shot of oil from the crank. The breather have a small half moon shape inside its tube.

[BrazilianZ28Camaro]

Again baffling is the key. Most custom of aftermarket valve covers do not have any baffling in them and almost always there is a rocker under and inline with the opening so the push rod oil hole squirts oil directly at the opening in the cover.
The opening at the rear on the passenger side is even worse as the oil is trying to drain there and fills the rear of that area and can be forced out by some base pressure at higher RPM.

I weld a 3" long baffle inside the covers the fill holes and PCV holes to avoid any splash induced oil venting in these areas. Helps keep things clean on the outside

Yes, the leak is on the passenger side breather.

Thanks for the tip Propower. This valve cover already have a baffle, but I think its not working as intended. Do you have a pic of the baffling you do on your engines?

[BrazilianZ28Camaro]

I just had to ad a baffle to my daughter's LS motor because there is a service bulletin about changing the cover. Even after all these years they still don't have this figured out. If it's only leaking out one side that's a very good sign. Should be able to do some type of mod to correct it.

Yes, its leaking just on the passenger side breather, the driver side is dry.

[BrazilianZ28Camaro]

From the picture: Just having the breather at the back of the motor is a issue in of itself.
Should be at the front of the motor, like the other side is.

Good to know this! I didn't find mirrored valve covers when I got those, and they came with the hole already drilled.

Righteous job on this car thou.

Thanks alot. You know how this sickness goes on and on........LOL