Crankcase Ventilation?

So as-bought, I have nothing connected to my air cleaner, no breather hose and a thermal snorkel connected to nothing. The valve covers are aftermarket (and chrome, and don’t look good as far as I’m concerned) and I’m not familiar with the oil filler cap on there and don’t know how to tell anything about anything anyway.

Is this maybe bad news? There’s nothing capping the breather tube on the air cleaner, it’s just sitting there open.

Is there a benefit to having an open vs closed system? Not sure I’m even understanding the difference. I’ve read some online (including everything I found with a search on and read through the shop manual too. Not really getting it.

I wanna understand all this sorta stuff, everything about how this car works really, but most important of all is I need to know if the way it is, as-bought, is bad news or potentially dangerous or would lead to crap performance or fuel economy or whatever.

As always, I really appreciate your help in getting my Cougar running best and keeping it that way. Thanks!!


Should have 1 pcv valve conected via hose to manifold or carb base and on the other VC a cap with a hose connected to the air cleaner. If you don’t vent enough the engine will blow oil out anywhere it can. For instance the dip stick tube or front and rear crank seals.

Lots of people are running open crankcase ventilation, witch means you have a filter on each valvecover, i did it too for many years, but recently changed over to closed venting again, due to the open system leaves an “oily” air in the enginebay, and that attracts dust and so.
The enginebay is easier to keep clean for a longer time with a closed ccv, i just put on a PCV valve on the right side (passenger side) valvecover, with a hose running from the PCV to the front centre inlet on the carb, some have it on the backside, or on the spacer, then a hose form the oil cap on the left side (drivers side) valvecover and into the airfilter, so it draws clen air from inside the airfilter

Not having the PCV valve hooked up could be a sign of a problem. I installed roller rockers and, because I’m using stock valve covers, I had to cut the baffles out. I was 200 miles into a road trip, and I noticed my oil pressure start to drop. I pulled over to the nearest gas station and checked my oil. Nothing on the dip stick. I went in and grabbed a couple of quarts. Still nothing. I ended up putting 7 quarts of oil in the engine. (Before you call BS, I had a deep sump Moroso oil pan with 8 quarts in the pan and one in the filter). I popped the PCV hose off the back of the carb and it was dripping with oil. Oil was being sucked into the engine through the PCV valve. I plugged my PCV system and completed the trip without a problem. It took me a little while to fix it and in that time I started to notice some seepage from my rear main seal. I picked up some baffled valve cover grommets and reconnected my PCV valve. Problem solved.

The previous owner could have had a similar problem. I noticed you have aftermarket chrome valve covers. Do your valve covers have baffles?

Showing my super noobness here, how do I know if they have baffles or not? I’m gonna swing by the garage today (hopefully) and check out exactly what’s going on with the valve covers and carb mount and try and identify the pcv valve (seen pics so I know what they look like). I’ve already read this part of the Engine section of the shop manual twice, and will probably read it a 3rd time before I go take a look and get a ton more pics with better detail.

Oh and fwiw, every time I’ve driven so far, the oil pressure has been very stable at 50. And I’ve checked the dipstick to find the oil right around the full mark when cold and actually above the full mark when hot. It has still never made it all the way up to the halfway point on the temp gauge.

To see if you have the baffles, take off the oilcap, or the filter on the valvecover, look in to the hole, if you see a metalplate just below the hole, then you have the baffle in place, or take off the valvecover and look inside, you´ll notice it instantly if it´s there

Pull the PCV valve out of the passenger side valve cover. If you see your rocker arms, you don’t have baffles. If you see a flat piece of metal, you do. You may also have something like this: … s=Rank|Asc

So I got this resolved I think. I posted a whole ton of pics in my “hello all” thread. Looks to me like my crankcase ventilation situation is all gold. Please have a look!

If you have a modified engine and are buzzing the motor past where Henry thought it should be OR your motor is getting tired, then more than likely the PCV won’t handle the volume of blowby the engine is producing. The result of not having enough crankcase venting is the dipstick blown out of the tube, intake end seals blown out, front or rear crankshaft seals leaking.

Hi Art, have you or anyone you know used an air pump for crankcase evacuation? Do you know what was used for an oil separator?

No and no.

I just had no breather connection to the air cleaner, so got inquisitive. But it just turns out that the silly chrome valve covers that were put on have a vented oil cap rather than a breather tube connection. It’s all good.

Bump of an old thread here…

I’m about to order new valve covers from WCCC and was wondering if anyone has experience with the aluminum finned valve covers?

Do they have built in baffles?

I have to assume they come with bolts, yes? They’re not the stupid post-with-a-wing-nut type piece at the top for tightening (and not measuring torque) are they?

Are they good?

Was looking at the running cat ones but I really wouldn’t mind saving half the cost, to put into other parts.


Here’s what I’m planning to buy for the valve cover update…

Finned aluminum valve covers

Rubber gaskets


PCV valve

Chrome vented oil cap with integrated tube

That all fit together right? I miss anything, or have anything I don’t need? I’m guessing the oil cap I have on my existing aftermarket valve covers is probably fine and might fit, but considering how dirty the oil that’s in the car now is, seems like its best to just go ahead and get some fresh crankcase ventilation parts in there, especially for the price.

Ask WCCC about whether or not the covers have baffles when you order, ask about bolts too, covers usually do not come with bolts in my experience.

Bumping this as it is the only thread with the FoMoCo manual terms to make life easier for future searches

The crankcase vent hose repros have 2 designations: C9OZ-6A664-A And. C9OZ-6A664-N
(There is a D too, but different form).

Can someone clarify the importance of the last letter? Unfortunately, I have plain…(heater hose?). It is not formed hose and it keeps popping off.


It means that the part is entirely different and had a different application. It’s a different drawing and a different part number.

These are available:

Thanks Royce,
The reason why I asked about “A” & “ N” is they both look identical to the shop manual pic.
from your response, I’ll be ordering A. Appreciate it!

Here are the pics for clarity in the question.

Sharing a perfect Murphy’s Law… this was the link I used to buy the part. It arrived yesterday, with this

Correct item number on the tag, correct item number printed on the part…wrong part. Holley got back to me today saying their entire inventory is incorrect. They hope to have correct part in the next 10 days.