PCV valve location

SBSerpent · #1 (**permalink**) 12-24-2021, 04:49 PM

I believe that I already know the answer to this dumb question, but does it matter which valve cover the PCV is on and which valve cover the breather is on? I want to swap the two for aesthetics.

Tommy · #2 (**permalink**) 12-25-2021, 05:49 AM

As no one else is rushing to offer an answer, I'll offer my opinion. I can't see why it would make any difference whether the valve or breather was on one side or the other.

twobjshelbys · #3 (**permalink**) 12-25-2021, 08:24 AM

Are you talking about front vs back of the same side or left vs right? If left vs right it does matter and they cannot be swapped. See the discussions about oil catch cans for the reason.

SBSerpent · #4 (**permalink**) 12-25-2021, 10:27 AM

Quote:

Originally Posted by twobjshelbys

Are you talking about front vs back of the same side or left vs right? If left vs right it does matter and they cannot be swapped. See the discussions about oil catch cans for the reason.

I'm talking left vs. right. The link you provided did not work. It just sent me to the Amsoil website.

tortuga · #5 (**permalink**) 12-25-2021, 10:37 AM

Maybe because usually the oil fill is on the drivers side? Also does the way the rotating bits throw oil, is there more oil ‘fog?’ On one side that the other? You would want the pcv on the ‘dryer’ side right?

In short i have no idea, mine is on the passenger side…

Merry Christmas 21

Steve H
Spf 1764

twobjshelbys · #6 (**permalink**) 12-25-2021, 11:55 AM

Quote:

Originally Posted by SBSerpent

I'm talking left vs. right. The link you provided did not work. It just sent me to the Amsoil website.

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.

twobjshelbys · #7 (**permalink**) 12-25-2021, 11:57 AM

Quote:

Originally Posted by tortuga

You would want the pcv on the ‘dryer’ side right?

No. The purpose of the PCV is to recirculate oil "blow by" and other leakages back into the intake combustion side. The amounts are miniscule and contrary to the catch can propaganda do not affect octane or any other operation. Unless something is dreadfully wrong.

SBSerpent · #8 (**permalink**) 12-25-2021, 12:35 PM

Quote:

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.

Ah, ok. So you're saying that there is an internal pressure differential between left and right sides of the engine? My PCV is currently located on the drivers side (Ford Racing Motor 392CID w/ Holley 750)

patrickt · #9 (**permalink**) 12-25-2021, 01:00 PM

Then why did Ford put the pcv on the driver's side in the 1978 Bronco?

patrickt · #10 (**permalink**) 12-25-2021, 01:30 PM

Nice shot of the Ford Bronco V-8. Ok TWOBJ, 'splain...

twobjshelbys · #11 (**permalink**) 12-25-2021, 02:02 PM

Quote:

Originally Posted by patrickt

Nice shot of the Ford Bronco V-8. Ok TWOBJ, 'splain...

Well, from experience....

On my 427 Windsor, I did not have PCV vented into the 8-stack. Instead I had some K&N filters...

One side (the side that all others have the PCV) the filter always had some oil on it. Had to clean it "frequently" (not because I thought it was clogged but because it attracted dust). The other side was always dry as a bone. Which side - I honestly don't remember.

The purpose of the PCV is to recapture those vapors.

Why the engine works that way was explained in one of the catch can topics. I think it has to do with crank rotation direction?

By the way, how do people that have 8-stacks connect a PCV??? When I registered mine I thought CO was going to make me have one but they didn't and I didn't ask.

patrickt · #12 (**permalink**) 12-25-2021, 02:16 PM

Quote:

Originally Posted by twobjshelbys

Well, from experience....

On my 427 Windsor, I did not have PCV vented into the 8-stack. Instead I had some K&N filters...

One side (the side that all others have the PCV) the filter always had some oil on it. Had to clean it "frequently" (not because I thought it was clogged but because it attracted dust). The other side was always dry as a bone. Which side - I honestly don't remember.

The purpose of the PCV is to recapture those vapors.

Why the engine works that way was explained in one of the catch can topics. I think it has to do with crank rotation direction?

By the way, how do people that have 8-stacks connect a PCV??? When I registered mine I thought CO was going to make me have one but they didn't and I didn't ask.

Then, if all that were true and were important and were related to crank rotation, why would Ford put it on the driver's side with the Bronco?

Tommy · #13 (**permalink**) 12-25-2021, 02:18 PM

First, I've not heard of the crankcase pressure being higher on one side of the engine than the other, and it doesn't sound right to me. Second, I looked at a few old threads re "catch can" and didn't see anything about crankcase pressure. So I'd like to see a link to the discussion that does. Third, I did find a discussion that suggested that the right side valve cover would have a higher oil level (and thus more oil droplets in the vapor) in race cars driven by high level drivers on a counter-clockwise course. That is because the G forces would pull oil toward the outside during the mostly left hand turns. As the OP is not likely to fall into this category of user, I stand by my earlier opinion that it doesn't much matter which valve covers has the PCV connection and which has the breather.

patrickt · #14 (**permalink**) 12-25-2021, 02:20 PM

Quote:

Originally Posted by Tommy

First, I've not heard of the crankcase pressure being higher on one side of the engine than the other, and it doesn't sound right to me. Second, I looked at a few old threads re "catch can" and didn't see anything about crankcase pressure. So I'd like to see a link to the discussion that does. Third, I did find a discussion that suggested that the right side valve cover would have a higher oil level (and thus more oil droplets in the vapor) in race cars driven by high level drivers on a counter-clockwise course. That is because the G forces would pull oil toward the outside during the mostly left hand turns. As the OP is not likely to fall into this category of user, I stand by my earlier opinion that it doesn't much matter which valve covers has the PCV connection and which has the breather.

What do you bet that if you hunt around you can find that exact same engine in something else from Ford, or a different year, that has the PCV over on the other side.

twobjshelbys · #15 (**permalink**) 12-25-2021, 04:31 PM

Quote:

Originally Posted by patrickt

Nice shot of the Ford Bronco V-8. Ok TWOBJ, 'splain...

A little closer examination will yield, as my old calculus professor used to say, "the answer is obvious to the casual observer". I'll disclose if you cry uncle.

patrickt · #16 (**permalink**) 12-25-2021, 04:31 PM

Or these...

patrickt · #17 (**permalink**) 12-25-2021, 04:33 PM

Quote:

Originally Posted by twobjshelbys

A little closer examination will yield, as my old calculus professor used to say "the answer is obvious to the casual observer". I'll disclose if you cry uncle.

If you're thinking the smog pump hose that's off matters...

twobjshelbys · #18 (**permalink**) 12-25-2021, 04:37 PM

Quote:

Originally Posted by patrickt

If you're thinking the smog pump hose that's off matters...

I'm going on a basic thing that is in the photo you posted. But its resolution is very low so I can't even see where a pump hose is.

Gonna be a while before I get back. Cooking two of the most beautiful filet mignons you ever saw.

patrickt · #19 (**permalink**) 12-25-2021, 04:41 PM

Quote:

Originally Posted by twobjshelbys

I'm going on a basic thing that is in the photo you posted. But its resolution is very low so I can't even see where a pump hose is.

I think the Ford diagrams are more reliable than any photo, because you don't know what the owner did before the pic was taken. But it sure seems like late 70's small block Fords all had the PCV valve located on the driver's side valve cover. I have no idea why and never even thought about it much until this thread.

cycleguy55 · #20 (**permalink**) 12-28-2021, 04:45 PM

Quote:

Originally Posted by twobjshelbys

A little closer examination will yield, as my old calculus professor used to say, "the answer is obvious to the casual observer". I'll disclose if you cry uncle.

The only thing I can see is that the passenger side mounting would place it very close to the firewall and the transmission dipstick tube. Placing it on the driver's side would avoid that crowded area.