PCV valve location

[twobjshelbys]

The 400ci is a cleveland.

[patrickt]

Originally Posted by twobjshelbys

The 400ci is a cleveland.

And why would that matter? And how 'bout the 351M in my Post 16?

[twobjshelbys]

Originally Posted by patrickt

And why would that matter? And how 'bout the 351M in my Post 16?

Cleveland and Windosrs are hugely different designs. I don't know about the 351, but don't have time to dig deeper. More important things to do right now.

My statement stands: Leave the PCV on the side in which it was installed.

[patrickt]

Originally Posted by twobjshelbys

Cleveland and Windosrs are hugely different designs. I don't know about the 351, but don't have time to dig deeper. More important things to do right now.

Uhhh, no... nothing is more important than this thread.

[twobjshelbys]

I keep waiting for Brent to pipe in. He knows...

A brief search (really, I don't want to spend more time on this right now) for "pcv which side" hits mostly on GM products, which I believe use the opposite side of Fords, but it always says that one side will have suction and the other pressure, and the pressure side is the PCV side. Why that happens I don't know - I'd think the engine would be rather symmetrical. But it is logical since if both sides had pressure (and thus large amounts of blow by) that there would be PCV on both sides.

[patrickt]

Originally Posted by twobjshelbys

I keep waiting for Brent to pipe in. He knows...

Brent hates PCVs. But I suspect if there is an answer, he will know it.

[sunman]

1973 stock truck 390. Fresh air in thru small filter that clips into air filter on drivers side.
PCV in cap ( or a rubber grommet) in back of pass side with hose into carb base plate.
I’ve had other pre 78 (non emission) Ford trucks that had the same.
The Bronco is missing the air cleaner with the small filter and hose that plugs into the grommet you can see on the back of pass valve cover.
Looks like Ford did it both ways
Drivers on left side

[cycleguy55]

Originally Posted by twobjshelbys

I keep waiting for Brent to pipe in. He knows...

A brief search (really, I don't want to spend more time on this right now) for "pcv which side" hits mostly on GM products, which I believe use the opposite side of Fords, but it always says that one side will have suction and the other pressure, and the pressure side is the PCV side. Why that happens I don't know - I'd think the engine would be rather symmetrical. But it is logical since if both sides had pressure (and thus large amounts of blow by) that there would be PCV on both sides.

In an OHV V8 the pressure would be equal on both sides because they're connected through the pushrod gaps and the lifter valley.

[Tommy]

The very nature of gases in an enclosed space and the principle of entropy means that even if there is a momentary local region of higher pressure, it will very quickly even out within the enclosed space. So if the crankcase pressure in one area (e.g., the driver side valve cover) were higher than that in another connected area (e.g., the passenger side valve cover), they would very quickly equalize. With all the blow-by pressure dumping into a common oil pan area, unless there was some system of intentional or unintentional one way valves inside the engine, I can't see how the crankcase pressure would be inherently higher under one valve cover than the other.

Credentials: BA Aerospace Engineering

[patrickt]

Originally Posted by Tommy

Credentials: BA Aerospace Engineering

Ehhh, I bet twobjshelbys has a BS in something, maybe everything....

[Gaz64]

Originally Posted by twobjshelbys

That link is one of the automatic links. You'll have to use forum search for "catch can". In essence, one side has positive pressure (the side with the PCV, which is why catch cans work, and the other side will be neutral or small vacuum (which is why catch cans on the other side don't get anything unless something is awfully broken). The PCV has to be on the high side.

That is a mechanical impossibility. Crankcase pressure is ALWAYS the same within any engine, left to right, top to bottom. Unless we have multiple crankshafts geared to together like in a square 4 or tandem twin.

[twobjshelbys]

Originally Posted by Tommy

The very nature of gases in an enclosed space and the principle of entropy means that even if there is a momentary local region of higher pressure, it will very quickly even out within the enclosed space. So if the crankcase pressure in one area (e.g., the driver side valve cover) were higher than that in another connected area (e.g., the passenger side valve cover), they would very quickly equalize. With all the blow-by pressure dumping into a common oil pan area, unless there was some system of intentional or unintentional one way valves inside the engine, I can't see how the crankcase pressure would be inherently higher under one valve cover than the other.

Credentials: BA Aerospace Engineering

Everything you say is true. But an engine is anything but a closed systemi. An engine has lots of moving parts that disturb the static environment. I do understand entropy. In fact, I got an A in Heat and Thermodynamics (one of my degrees, there are more).

Let's just say that which side defies intuition based on all of our static analysis. Intuition says that the system should be balanced with equal pressure on both sides. The empirical data supports that one side is suction and the other side pressure. The fact that the 390 (probably a FE) picture has an open cap on one side with no evidence of exhaust and the PCV (pressure) on the other supports that. The same was true on my Windsor with no PCV but with the K&N filters - one side had oil from the inside to outside and the other was dry. And similarly, if both sides were pressure, I'd guarantee you that Uncle Sam would demand PCV hardware on both sides. Noone here understands why it works this way, but the fact remains, it is a fact. It defies logic and intuition. Sorry, I'm not trying to define why it happens, only, from the beginning, reporting my observations. Sorry if you're looking for something beyond that, since you're not going to get it from me.

Also, while other engines may be interesting, the OP was asking about Windsors. It is consistent with my catch-can observations on my supercharged Shelby GT which was the 4.6L 3V modular combined with others that have put catch cans on both sides and observe they never "catch" anything.

So the message to the OP is: Leave the PCV where it is.

I'm not sure the consequences of changing it would be pretty: As configured, minute amounts of oil but certainly some amount of pressured gasses go from the engine to the air intake. I don't know the volumes or pressures involved. If you reverse the configuration all of a sudden the suction/vacuum side will pull stuff from the air cleaner area to the top of the engine. Think about it carefully. Then try it if you feel lucky but please report back here.

I still think Brent is the only one that can explain it. I'm not going to try to solve it myself. I'm no longer interested in investing research and learning for something that I will only use once, 20 years ago maybe, but not now. My brain is full. I'll look for an expert to explain (similar to drywall, there are experts that can do that).

[Gaz64]

Oil inside one breather filter and the other side dry is more to do with position front to rear of each breather. Are they both at the front?

Otherwise I still say can't happen.

PCV valve should be placed as high up in the engine, and so moving to the front of the engine, either side, is likely to have less splash oil go through the PCV valve. Factory baffles plates aren't very good, and some aftermarket are even worse.

Whichever side has the PCV valve, the other side is the fresh air inlet, and flows air in BOTH directions.

https://www.google.com/search?q=pcv+...ih=791&dpr=1.1

[SBSerpent]

Originally Posted by Gaz64

Oil inside one breather filter and the other side dry is more to do with position front to rear of each breather. Are they both at the front?

Otherwise I still say can't happen.

PCV valve should be placed as high up in the engine, and so moving to the front of the engine, either side, is likely to have less splash oil go through the PCV valve. Factory baffles plates aren't very good, and some aftermarket are even worse.

Whichever side has the PCV valve, the other side is the fresh air inlet, and flows air in BOTH directions.

https://www.google.com/search?q=pcv+...ih=791&dpr=1.1

PCV is front of DS valve cover; breather is at the back on PS valve cover.

Why would there be more oil splash at the back of the valve cover vs front of the valve cover?

[patrickt]

I think the only reason the cap is on the front of one valve cover and the back of the other is because both valve covers are really the same. When you put the cover on one side of the engine the cap is on the front and if you put it on the other side it's on the rear. I think that's the only reason.

[sunman]

Valve covers are baffled if you have oil coming out you have a blowby prob.
Here’s a photo of a 73 Ford 390 FE driver side and 86 Mustang 5.0 HO pass side.
The 86 5.0 driver valve cover has no holes.
My early Chevy small blocks had a PCV in the vent hole next to distributor and a vented cap in intake manifold oil fill tube. A big oil separator bolted in the lifter gallery. The valve covers had no holes, said Corvette on them, good times

[Gaz64]

Originally Posted by SBSerpent

PCV is front of DS valve cover; breather is at the back on PS valve cover.

Why would there be more oil splash at the back of the valve cover vs front of the valve cover?

I would say because of the rearward tilt of the engine.

[patrickt]

Originally Posted by Gaz64

I would say because of the rearward tilt of the engine.

And maybe because you're driving forward.

[Gaz64]

Originally Posted by sunman

Valve covers are baffled if you have oil coming out you have a blowby prob.
Here’s a photo of a 73 Ford 390 FE
My early Chevy small blocks had a PCV in the vent hole next to distributor and a vented cap in intake manifold oil fill tube. A big oil separator bolted in the lifter gallery.

Note the blowby airflow has to make an abrupt turn which helps fling oil out of the air.

[Gaz64]

Originally Posted by patrickt

And maybe because you're driving forward.

Yes, acceleration G force is under load, more blowby. Deceleration Gs are under coast, less blowby.