View Full Version : PCV (Positive Crankcase Ventilation)

06-23-2013, 09:15 PM
Since PCV is under the 4 letter minimum search criteria and I doubt anybody is going to take the time to type out positive crankcase ventilation.........

This is on a 352 FE with the original 4100 Carb. The car originally did not have PCV but I am adding it because I changed the engine in my car and this new one doesn't have a road draft tube. I'm also using some new chrome valve covers (bling!).

To obtain the PCV vacuum I decided to use a carbuerator spacer with PCV like this one (as long as the ebay link holds up) - C8SZ-9A589-B. Seems to work great.


After installing the PCV plate under the carb I have 20 inches of vac at the valve cover using an old Nissan PCV valve I had laying around.

Questions are - is this a good reading at the valve cover (high idle - choke on - about 1000 rpm) and what PCV valve should I use?

Looking for a right angle valve with 1/2 inch output (same size as the PCV plate input) and 1 1/4 push in for the valve cover grommet. I can find one easily by just using a Mustang, Torino, etc as refrence but wondering if this is too much vacuum and if there is one needed that regulates the vac by the size of the orifice.

Any help, suggestions, ideas or laughter is appreciated - :D.


(PCV will replace the existing valve cover vent)

06-23-2013, 09:52 PM
Got a 352 engine? Get a valve designed for a 350 or 351 engine, made over many decades. Just make sure the flow goes toward the intake or carb plate. PCV's are made in both directions. If an arrow is not stamped on the outside, blow into it hard. If flow stops, output is on the engine side.

PCV valves do not control vacuum. They simply use a spring offset prindle to act against vacuum pressure to control how much flow passes. It closes off completely like a check valve in one direction because you don't want fuel mixture coughed into your block if the engine backfires.

Anywhere around 18-20 inches of mercury is acceptable vacuum for power brake booster operation.

06-23-2013, 10:48 PM
Well some of them must regulate - I read it on the internet - and everything you read on the internet is true........ :D

Many thanks Dave. The search is on for a 90 deg. with the right dimensions. So far it looks like a Fram FV202 might work but plenty to look at. Just a matter of guessing the right vehicle and seeing the dimensions of the parts. (Only way I have to check them anyway) Plenty of straight ones with the right dimensions....:mad:.


06-24-2013, 12:37 AM
Go for either a STANDARD MOTOR PRODUCTS Part # V190, a Stant 10071 cam-lock valve cover cap (http://www.rockauto.com/catalog/moreinfo.php?pk=48457&cc=1120004), and a PCV grommet (DORMAN Part # 42065)

06-24-2013, 07:58 AM
Unfortunately both valve covers have the same small grommet hole so the breather will have to be the 1 1/4 push in style (a small one to clear the air cleaner snorkel plus use as the location for oil fill - no filler neck on the intake)

Most likely it will be a Mr. Gasket 2056
Possibly a K&N but I don't really like the exposed screen look. If it fits though.....

I'll add the V190 PCV valve to the list of ones to check at the parts store - looks like a good fit.


06-24-2013, 04:23 PM
Eric, it's important that the breather has a mesh inside to coalesce the oil. That means the mesh cannot expose to the outside as it is part of the vapor path to your intake.

To clarify, do your rocker covers have twist-lock holes with baffles underneath the openings?

06-24-2013, 08:23 PM
Naaa - they're cheapo valve covers. Wasn't sure I would like them so went with the cheap ones for starters. They both only have a grommet hole - no locking tabs underneath - :o

The Mr Gasket 2056 breather info is listed as....."It has metal baffle/foam element"

If it fits without interference it's probably my best bet because of it's smaller size - it's the smallest breather I can find - there are other smaller plain caps that are not breathers.


06-24-2013, 08:36 PM
If you use a breather/oil-filler cap that's not designed to hook up to your air-filter you can put one of those elastic cotton 'sweat-bands' around the base of the breather. (The thing that tennis players have around their wrist to wipe sweat from their forehead!)

This pretty much stops blow-by oil from running down your valve-covers!
(a.k.a 'tappet-cover' here in NZ)

Just remove the sweat-band twice a year and rinse it in de-greaser.

06-24-2013, 09:37 PM
Probably where K&N got their idea - you guys should have patented that......

This one should work much like the original system and has the filter built in but rather than "draft" the vapors out of the road draft tube I'll be sucking them back into the engine via PCV port under the carb. Those breathers that hook to the air cleaner usually don't have a filter and rely on the air cleaner element to filter the air.

Your MOT lets you get by with a sweatband in the engine compartment? - :eek:

Tappets - now your talking my language - that's all the MG guys call them other than cam followers.

Thanks for the ideas though - might come to that.


06-24-2013, 11:08 PM
(Cam followers and lash adjusters are used in overhead cam systems with no pushrods.)

The valve covers I'm using on Penelope's 390 are stock '73 Ford covers with cam-lock and baffles. Nothing fancy, painted Ford Blue. One of the covers had a rubber plug which held the PCV in place.

I took the rubber grommet out and replaced with a Stant breather. This Stant has mesh inside with one hole on top and none around the outside. (Hope I explained that right.) It's important to remember that air needs to ENTER the engine from the opposite valve cover.

You mates down under, if valve covers are called tappet covers, what do you call valley pans? - Dave

06-25-2013, 12:21 AM
You mates down under, if valve covers are called tappet covers, what do you call valley pans? - Dave

Not many motor still with them Dave - but in my Y-block days we called them 'valley covers'!!