No valve cover breathers?

[Krooser]

Went to the stock car races Saturday night to help my buddy.. he runs a late model at one of the local dirt tracks.

He had an oil leak from the fuel pump cover... turns out he plugged the oil return line in the block rather than the oil supply port...made sense. He's running a KRC tandem fuel/power steering pump driven off the rear of the crank.

Then in the feature he was being blinded by oil leaking from the right side valve cover gasket. While searching for the source of the leak I noticed he didn't have any breathers on the left side valve covers. Didnt really hit me until the ride home...

This is a SBC with a five stage dry sump system. I believe he did have breathers last season... same motor and dry sump but in a different chassis.

I'm thinking this no breather deal is a recipe for more oil leaks...

[KnightEngines]

If it's sealed up tight & pulls vac it's a recipie for no oil leaks!
If it's leaking it's not pulling vac, only takes a small air leak to kill vac.
Tell him to seal it up better, not only will he not be blinded by oil mist he'll also be up some hp.
But make sure he runs a vac relief set at a max of 12" - more vac than than on a motor not set up for high vac will hurt things.

[Krooser]

I get it....as long as it's tight the vac side of the pump will take care of it.

I guess my zero experience with dry sump system shows!!!

Now if I could just keep that light bulb burning....

[MadBill]

It's also a good idea to install a permanent crankcase vacuum gauge. It provides a running report of external and internal (rings) sealing.(e.g., if it drops at WOT, the rings are losing seal. If just at high RPM, it might be ring-flutter.
It should take upwards of 60 sec. to bleed off all the vacuum after shutdown.

[Krooser]

Guess I'm too dumb to have all this fancy stuff... My son lost my when he installed a water pressure gauge on his race car...

[andyf]

I've seen a lot of dirt track or lower end paved track cars run valve cover breathers in their dry sump engines. I do not know why they do that but they do. Most drag race guys run sealed engines with dry sump and just have a breather on the tank. I know the higher end circle track cars run sealed engines since they pull a lot of crankcase vacuum, but the local circle track guys run breathers. Last time I asked a circle track guy why he had breathers in his valve covers he looked at me funny and said that was the way they've always done it.

[MadBill]

In another thread I reported helping a circle track racer dyno his ~ 400 HP dry sump SBC. After jetting and timing yielded ~ 8 HP, I said "Lets plug the breathers". Poof: +13 HP.

[Krooser]

Guess I'm too dumb to have all this fancy stuff... My son lost me when he installed a water pressure gauge on his race car...

[Alaskaracer]

Dry sump here, sealed engine, and relief valve on the vac pump (Star pump) set for as high as it will go.....no issues!

[leahymtsps]

A few yrs. back I had someone bring in a BBC with no breathers and a 12 fitting welded into the
valve cover. I asked what the fitting was for and the response was

"I run the vent line from the oil tank to the v/cover to keep it sealed up!"

Needless to say it had several leaks.

Tom

[Warp Speed]

A few yrs. back I had someone bring in a BBC with no breathers and a 12 fitting welded into the
valve cover. I asked what the fitting was for and the response was

"I run the vent line from the oil tank to the v/cover to keep it sealed up!"

Needless to say it had several leaks.

Tom

That was the way it was done in the early 90s.

[MadBill]

..That was the way it was done in the early 90s.

Do you jest Warp, or do I misunderstand the OP? It reads to me that there is no path to atmosphere for blow by gases...

[Kevin Johnson]

It is sustainable for a period of time. Twenty-two point four liters of gas are present in one mol of water and the liquid measure of that water is about 18ml -- this is the concept. Adjust for the average molecular weight of a paraffinic oil and the specific gravity of that oil.*

The blowby gases continually present new "atmosphere" to use potential dissolution volume that is available (about 9% by liquid volume per internal atmosphere differential, via Henry's Law). The key requirement is vacant space in the holding tank which then gradually fills with a fluid that is a homogeneous mixture of dissolved gas and lubricant.


* See Table 1.
https://reader.elsevier.com/reader/sd/p ... C30777B560

[leahymtsps]

..That was the way it was done in the early 90s.

Do you jest Warp, or do I misunderstand the OP? It reads to me that there is no path to atmosphere for blow by gases...

Morning Bill
That's exactly the way he had it, completely sealed and not vented to atmosphere.

Tom

[Warp Speed]

..That was the way it was done in the early 90s.

Do you jest Warp, or do I misunderstand the OP? It reads to me that there is no path to atmosphere for blow by gases...

Back in the late 80s, early 90s, many would run a breather line from the valve cover to the tank. That way, if there was any crankcase pressure getting released, it would be vented to atmosphere through the breather in the tank, instead of the engine compartment, through breathers wrapped in shop rags! Lol
That was before the use of crankcase depression. Even shortly there after, you would run the same vent line, but with a one way check valve. That way it would hold crankcase depression, but in the event of a failure and pressurization, it would still vent to the tank.
Now, most proper systems are sealed tight at the engine. Provided they have enough scavenging to create a depression.