Valve Cover Breathers or Not?

[TheJet-09]

Way back when it seemed like two breathers in the left valve cover was the norm, but anymore I see many engines that have only one breather, and even some that have no breathers at all. My question is, on a dry sump DLM engine, what determines either the need to have or to not have valve cover breathers on an engine?

[TALON75]

The "breathers" you see are in fact a one way pressure valve . Dry sumps are normally under vacuum, the valve is there to vent pressure if needed like when a piston gets burned and puts combustion pressure in the pan. I think it just helps it from blowing out the main seals so there is not a huge loss of oil and may save other parts. Our D!ckens engines have no valves, Cornett's do.

[powerslide]

So talon you guys just have a pop off valve on one valve cover?

[hucktyson]

That's correct just a Peterson blow off valve on 1 cover without and breathers. Clements and Cornett both do it that way.

[fastford]

I also run one pop off valve and vent the oil tank. I never ran a pop off valve on a 3 stage pump and never had a problem, even though now I would recommend it, but when I went to a 5 stage I had some issues and put one on and never had another problem.

[JHobbs26]

does the engine require special main seals if you are pulling a vacuum? Thought I read/heard that somewhere, you couldn't just use a standard type main seal.

[RayburnBaby]

Most engine builders will tell you that 7-11 pounds of vacuum on a drysump engine also makes about 25-30 more HP. An the drysump tank can breath it has its own breather system.

[Brian Gray]

Most of mine I'll put a check valve in the manifold valley to allow pressure out be there any residual inside the engine. The dry sump will pull enough vacuum to aid in ring seal but additionally the negative pressure will increase oil flow to key areas. For example 80 psi at the pump multiplied by the negative inside the engine doesn't increase the pressure but will help draw more volume through the system. The system is also vented at the tank.

[hucktyson]

Brian there's dudes who turn the 550 cat in their hauler more rpm than you do on the race track ... Does that even require a drysump ??