Valve covers PCV and Breathers

[CSX3183]

For 7 years I and 7,000 miles, I ran CSX 3183 with a road draft tube from the rear of the intake and the intake oil fill tube with a oil cap on it. Never had any oil residue on the intake, or any oil, gunk, goo or mist from the tube.

Run the Pentroofs, without holes, get the "RIGHT LOOK" period correct, and never worry, if it worked originally , and worked for me, it will work for you.

[car4jim]

There is another factor which I don't recall being discussed which is compression blow-by the piston rings building pressure in the crankcase. There needs to be sufficient ventilation from the crankcase or pressure will build. I have similar questions on how to structure the crankcase ventilation system. I have a Keithcraft FE stroked crate engine that has a hose from the drivers valve cover to air cleaner carb intake, a puke tank with road draft and connection to the rear intake manifold and crank case and a vented oil fill cap and I still blew the oil fill cap off the breather at Fontana this summer. It seems my engine needs more crankcase ventilation area. Any idea how much bypass flow is created by the oil rings at 4000 RPM, etc? What is a acceptable positive crankcase pressure?

[DanEC]

Originally Posted by car4jim

There is another factor which I don't recall being discussed which is compression blow-by the piston rings building pressure in the crankcase. There needs to be sufficient ventilation from the crankcase or pressure will build. I have similar questions on how to structure the crankcase ventilation system. I have a Keithcraft FE stroked crate engine that has a hose from the drivers valve cover to air cleaner carb intake, a puke tank with road draft and connection to the rear intake manifold and crank case and a vented oil fill cap and I still blew the oil fill cap off the breather at Fontana this summer. It seems my engine needs more crankcase ventilation area. Any idea how much bypass flow is created by the oil rings at 4000 RPM, etc? What is a acceptable positive crankcase pressure?

I think I would talk to Keith's shop about that. That sounds like more positive crankcase pressure than you should have from a custom built motor. I assume the oil fill cap/breather had good tension on the retainer clip?

[Al G]

Originally Posted by chanmadd

al..... How many miles on your car?...

2300.

[DanEC]

Originally Posted by cscobra

PCV: Required in California model year 1962, rest of United States 1963 model year. Some manufacturers opted to start before these dates.

That sounds more like it but I know Corvettes ran road draft tubes on their small blocks up until 67 or so. And I think 427 Galaxie's did also at least in 63 but I think in 64 also. Maybe they stuck a PVC valve on there also. If so it probably was marginally operable with the road draft piping.

Correction - after more looking I see that some Corvette's as early as 64 ran a PVC hookup off of the oil fill tube. Not sure what tney did with the draft tube - left it operational or blocked it off.

[Danr55]

As you can see there is no breather or PCV coming from the valve covers.. There is what looks like a PCV coming from the intake manifold and a oil tube/breather on the right side of the manifold. Motor runs great and no sludge/gunk/crap build up of any kind.. Besides that give me an excuse to "blow out the motor" once in a while..

[xb-60]

Originally Posted by Dimis

Ok, thanks. So here's the follow on question.

Conceding its best practice to run both pcv and breathers through the valvecovers.
If I run a pcv through the back end of a TW manifold back to the carb, in an attempt to use bald chrome pentroofs on my engine, how much sludge and gunk would I expect would accumulate in my cobra?

Thx again.

Dimis - what polution requirements do you have to satisfy?
Cheers,
Glen

[Dimis]

Originally Posted by xb-60

Dimis - what polution requirements do you have to satisfy?
Cheers,
Glen

Not sure. Just wanted to make sure I'm not ruining an engine, and "gunking" it (is that even a word) all up on the inside.

[Barry_R]

Gunking is very unlikely.

Depending on the atmospheric conditions you are running in you may get some white/gray jelly and moisture condensation on the underside of those unvented valve covers. The covers are the physically highest point in the crankcase, and are exposed to cooler outside temperatures - hence they will be where any condensation forms. Ford and GM moved their ventilation from the intake to the valve covers 45 years ago for a valid reason.

If cosmetics are critical - and I personally see that as a legitimate concern - then you need to have a PCV of some sort just to promote airflow through the engine in an effort to purge vapors. If located in the rear of the intake as commonly done you need to do extra work to prevent oil leakage and consumption - baffles and a liquid containment loop in the vacuum lines will help. But you are now reliant upon just the oil breather cap area for WOT ventilation and that may not be adequate for some engines under high RPM loads.

This is not a new problem - those tall "S" shaped breathers and catch cans all came into being for a reason...

[ERA Chas]

It's great to see Barry weigh-in here and we need him to do that more often.
But the silly man places a priority on making a living rather than educating us with his experience.
All his points are valid-no contest. But I can say from my experience, in my case, the open fill tube breather and the rear intake-mounted PCV causes no issues such as he mentions. And yes, the valve IS working.
The sheet metal tray in the valley prevents liquid (not vapor) from being pulled through the valve and line. The engine stays clean and the exhaust smoke-free. The Pentroofs never have the moisture milkshake. In fact, I used to run the S-shaped rear breather he mentions and it caused oily sweat but not dripping wet. This PCV solved that.
But one should certainly check for those signs when installing a PCV system.