No valve cover breathers?

[MadBill]

Yes, it has evolved. I like to seal the engine tight, but also run a big check-valved vent hose from the engine to the tank so that if a major blow by issue develops, at least it's not popping gaskets and igniting on the headers.

[FC-Pilot]

I have seen boat guys run them with breathers on the inside valve cover (circle racing) with the vent from the tank connected to the outer valve cover. So the inside valve cover is what vented the blowby. I don't know why, but saw several circle boats set up this way.

Paul

[MadBill]

Sounds like they're counting on the cornering force acting as an oil separator, centrifuging most of the oil mist to the outboard cover and hence to the tank, so that only gases exit the inboard vent. If I'm understanding correctly, it doesn't seem like as good an approach as the previously discussed vacuum pan.

[leahymtsps]

Morning Jay,
The way you are describing it is it has a breather on the tank and is venting, but the way I'm telling it is there was no breather on the tank. The
tank had a line that should have run to a breather but he ran it to the v/c instead, completely sealing the system less the leaks. I've seen what
you've described and this wasn't like that.

Tom

..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.

[Warp Speed]

Morning Jay,
The way you are describing it is it has a breather on the tank and is venting, but the way I'm telling it is there was no breather on the tank. The
tank had a line that should have run to a breather but he ran it to the v/c instead, completely sealing the system less the leaks. I've seen what
you've described and this wasn't like that.

Tom

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.

Wow, he'll never get that system to quit pushing gaskets! Lol

[Kevin Johnson]

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.

If the residency time in the tank is low and the swirl deareation system marginal the oil will gradually be populated with small air bubbles and reach the dissolution saturation point at one bar. Even assuming they are driven into solution by the pressure stage, when they emerge from circuits/bearings/lifters they will foam and slowly break and drain. Air entering the top of this system will help push or encourage the flow to the scavenge ports thereby decreasing the transit time back to the holding tank. The rate that the oil is replenished is obviously critical.

AVR Schrick has a nice articulated dyno system but as we know, the weakness there is that the system itself cannot be accelerated. Track testing is therefore important. Going back, OEMs have tried tilting the whole vehicle to test systems (Formula SAE as well).