Why don't both valve covers have holes?

The PCV sucks out from the valley pan and goes into the carb.

But only one valve cover has an air inlet? Does that cause issues?

Just wondering why.

 

The idea is to "Ventilate " the crankcase . Only need 1 air entry as it encompasses the lifter area and thus the entire engine .

 

Actually allows PCV to move air faster with one breather.....IMO
Air is drawn in at valve cover unless there is so much blowby that it is too much for PCV to handle.

 

The PCV system is designed to seal the crankcase from the atmosphere.. under all operating conditions.. it was the first pollution control, adopted in the mid 60's.

Under part throttle operation, the PCV valve is sized to be able to remove all combustion gas blow by, and re-introduce that mixture into the intake stream, to be burned. It does this by using intake vacuum to suck the gases out of the valley area. Clean air is sucked into the crankcase, via the breather hose, to prevent the system from sucking a vacuum in the engine. This was done for 2 reasons: Those engines were not designed to run in a vacuum, and the extra clean air helped burn the combustion by products up in the engine.

At WOT, no vacuum exists, so the system then functions differently...pressure buildup is ventilated thru hole in the Driver side valve cover, thru the breather hose, back into the air cleaner assembly, where it is again introduced into the intake stream, to be burned.

Hi Performance engines operate at higher rpm, and much higher cylinder pressures, so there is naturally more blow by, which is why all performance engines should have at least two valve cover vents. Few find the need to run them to a sealed air cleaner, standard practice is to just run them open to the atmosphere.

I have heard of instances were very high HP engines actually picked up HP by adding a breather.

I recommend any engine over 500 HP have at least two valve cover breathers, and I run a pcv valve in all my engines, unless they run a vacuum pump.

JW

 

I often heard a similar comment from my dad growing up, then when something broke he would say 'Why don't you add another (enter modification here) '

 

Jim...on my Jag I have the PCV connected to one valve cover (ala Chevy) and breather on other one. Would I be better off connecting to valley? Full fumes better...?

 

You must have changed them then.. last time I saw it, it was wearing chrome stage 1 covers..

For guys with those covers, to add another breather, just order a TA 1335A oil cap/breather, and replace the oil cap with it. Does not matter if you have two breathers on one side.. or one on each. It's purely a volume thing.

The other issue we have is that there are no baffles built into either the stock or aftermarket covers to shield them from having oil pushed out, with a high performance type breather. You can use a baffled grommet like this:

https://www.summitracing.com/parts/...HXA_mu7gF4RVN_2SHLlOc-19-jW9jsGkaAjHJEALw_wcB

or fab some kind of baffle inside the cover..

JW

 

Ya, and more importantly it will get you to put a shield on the bottom of the intake, to keep from basting it with hot oil.. LOL.. ok, maybe you did that already... seriously, I doubt it makes any difference, valley or valve cover. We don't worry about it with a vacuum pump inlet. I have done that both ways, no difference.

JW

 

I use a MOPAR style breather to suck the fumes. Has internal baffles and doesn't seem to suck oil.

 

Good to hear Larry, ya stamped steel covers and TA alum heads are a pain..I have went to having the undercut machined in the intake side of the heads, so the steel valve covers fit properly, without spacers or ridiculous thick gaskets. A lot of guys are running stock rockers these days with those heads, and need no extra room under the covers.

For your engine, that is the best setup, and looks sharp..

JW

 

Ya, used those with the pan evac system I had on my race car, years ago..

JW

 

Hmmmmm he says. Hey Jim, do the valve covers I sent back for my engine have openings on both covers? I have a set of chrome edelbrock covers here and one cover is solid, the other has 2 holes.
I can't remember what the original covers looked like orif there is any kind of baffle in the stock covers.

Oh, and what do you recommend for my engine? Should I add another hole?

 

Jim, do you see any problem of running the PCV in the valve cover and the breather in the rear of the Edlebrock performer intake ? This is how my engine builder mocked things up.

 

I forgot to order the preformed PCV hose TA 1240D so he figured out it'd look neater to run a short hose to a hole in the valve cover