Valve cover breathers - Team Camaro Tech
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post #1 of 9 (permalink) Old Nov 29th, 16, 10:25 AM Thread Starter
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Jim
 
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Valve cover breathers

I've seen various setups for breathers...some hooked together, some connected to a PCV, others just standalone...

Getting ready to start engine for the first time, hopefully in the near future.
What's the correct breather setup?

Jim
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post #2 of 9 (permalink) Old Nov 29th, 16, 12:16 PM
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Re: Valve cover breathers

Since 1963 a PCV valve and a breather in either the valve cover (messy), or inside an enclosed air cleaner. When you need ventilation the most at high RPM the PCV is drawing the least volume of oil laden air into the engine as manifold vacuum falls at higher RPM.

Race cars use a mechanical belt driven vacuum pump to suck out the fumes (and excess oil that can be drained back into the crank case later). In doing so they gain up to 25 more horsepower than required to power the pump due to better ring sealing and less windage.

Roundy round cars racing on dirt tracks use a tube bridging the valve covers with a pair of breathers on tall tubes to separate the most oil from windage. On pavement they use a mechanical vacuum pump and recovery system.

Finally they used to allow vacuum created by a venture in the exhaust collector to evacuate the oil laden air but I haven't read a NHRA rule book in over two years so that may have changed.

If you use a breather without a source of vacuum to evacuate the pan you will have oil all under your hood coating everything.

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post #3 of 9 (permalink) Old Nov 29th, 16, 01:22 PM
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Re: Valve cover breathers

Quote:
Originally Posted by Lobstah View Post
I've seen various setups for breathers...some hooked together, some connected to a PCV, others just standalone...

Getting ready to start engine for the first time, hopefully in the near future.
What's the correct breather setup?
Hey Jim. I'm not sure how correct you want to get, but from the factory there is a PCV valve in the DS valve cover and it's routed to the base plate on the rear of the carb for the vacuum source. The PS cover has a hose routed to the air cleaner.
On mine, I run the DS like factory going to the back of my Holley carb and then I have a stand alone filter on the PS. I haven't had any seepage issues and a lot of guys have run them like that. We'll see what happens on my new motor. I'm betting the same...






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post #4 of 9 (permalink) Old Nov 29th, 16, 01:43 PM
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Re: Valve cover breathers

Old days used a draft tube to pull fumes from the crank case. Then the PCV system and into play mostly because of EPA requirements.

That said the PCV system is genious in it's simplicity.

The breather tube to the air filter base assures filtered air came into the crankcase. A filtered breather does the same thing.

The later becomes and issue if you have CC pressure that exceeds the available vacuum and air is forced out of the breather. That's hat makes the mess in the engine bay.
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post #5 of 9 (permalink) Old Nov 29th, 16, 04:23 PM
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Re: Valve cover breathers

What about the oil vapors that get into the combustion chambers? Oil vapor can cause detonation and carbon buildup on the piston casing both hot spots and raising the compression. At least that is what I was told. Like Dave said above vacuum pumps are for race cars. I have two breathers and would like to hear good ideas on this subject also.
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post #6 of 9 (permalink) Old Nov 29th, 16, 04:52 PM
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Re: Valve cover breathers

On my 70, I run 2 breathers and no PCV at all. Been like that for many years now with no problems.




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post #7 of 9 (permalink) Old Nov 29th, 16, 05:55 PM
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Re: Valve cover breathers

The longer the stroke with a stock depth oil pan the more windage you will create. Rev that long stroke up and you can actually loose 25 horsepower as it is used to beat returning oil into foam.

Today I use windage trays, oil scrapers, and I open up the front oil return holes in the timing chain cavity while blocking off the holes above the crank with screens. I also paint the interior of the block with Glyptal paint to enhance and expedite oil return and exercise some measure of control. That said; from my Corvair to my 283's and 327s SBC stuffed into my 55 Chevys I was always spraying engine Shampoo (nothing more than kerosene and dish detergent in an aerosol can), and washing off oil from these engines. Part of this was my reliance on the needle bouncing off my ten grand tac to tell me when to shift. The other part was I used four M/T breathers in my valve covers that had little to any filtration, but look really good.

My 582 never spilled a drop of oil. I ran a single PCV with a breather on the end of a molded rubber hose stuffed inside my Holley Dominator's K&N air cleaner (using the Corvette and Chevelle BBC ninety degree plastic El) as I was trying to pass the engine off as a 402 BBC pick-up truck engine with an exhaust leak and looking stock helped sell the act.
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post #8 of 9 (permalink) Old Nov 29th, 16, 06:16 PM
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Re: Valve cover breathers

Dave, race cars and street cars are diffferent animals.

Lots of guys do not run pcv systems and just breathers in the valve covers. Been there done that.

PCV systems get the corrosive gases and fuel out of the crankcase.

Weekend drivers IMHO need a PCV even more as they sometimes don't get to operating temps for long periods of time.
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post #9 of 9 (permalink) Old Nov 29th, 16, 06:33 PM
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Re: Valve cover breathers

I agree with you John but not everyone goes to the track to open up their car.

I even confess to a little street racing back in the sixties despite my having a key to the front gate of a local quarter mile long drag strip in my pocket. It was a case of instantaneous gratification (at least for me, as I seldom lost because I drove what I raced either a B/G or an A/MP Camaro or Nova on the street as a daily driver carrying a bag of rosin and a gallon of bleach in the back seat). I didn't make a habit of it as I was paying for my car working as a street cop and didn't need to explain to my superiors what I was up too back from 1967 through 1970. After that I was working as an engineer with a race car fab shop on the side.

Actually it wasn't until ten years ago that I finally recognized that age was catching up with me and I stop deriving a nine second car on the street. Makes me wonder how Chris Karamesines does it.

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