289 FIA valve covers and positive crankcase vent

[seatra]

While looking at photos of CSX 2345, I noticed that the left and right valve covers appear to be stock stamped covers finished in chrome. Both covers appear to be the oil filler/vent cap style. (no PCV port). I know PCV was just becoming a thing back then. Looks like both oil fill caps vent off to their own puke tank mounted on either side of the engine bay. Was there a reason PCV was not used on this setup? Perhaps the flow of crankcase gasses at high engine RPM affected ENG/CARB tuning. Maybe the intake manifold didn’t have a vacuum port designed for this gas recirculation. I am prepping a 1965 289 for my FIA replica and am on the fence about replicating this valve cover vent set-up. Other than oil puking into the tanks, is there any negative issue with not running PCV? Anyone have identification information for those caps and puke tanks on CSX-2345?

[Tommy]

In general a PCV system serves three purposes. It burns vapors that would otherwise escape into the air. It can reduce crankcase pressure to lessen oil leaks at seals and enhance engine performance slightly. And it can reduce contaminates inside the crankcase allowing oil to remain cleaner longer.

The Cobra I once owned was built for street and track use with no PCV and a catch can plumbed to the closed valve covers. I changed the oil and emptied the small amount in the catch can before each track event. Other than negligible damage that may have been done to the environment, I saw no disadvantage to that system. Had it been a car that saw 15,000 miles per year, my answer may have been different.

[CompClassics]

How do you plan to distribute the crankcase vapor to all the cylinders evenly on a Weber system? A better question would be, why would you want to?

[1985 CCX]

Cannot find mine.
Also missing thermostat ?????

[seatra]

Originally Posted by CompClassics

How do you plan to distribute the crankcase vapor to all the cylinders evenly on a Weber system? A better question would be, why would you want to?

Good point. I've never had a Weber system so I was not sure about the manifold ports, vacuum, etc. on those 8 stack configurations. My only interest would have been to establish crankcase ventilation, which does not appear to be an essential need. Any idea where I can get the catch cans and Oil fill/vent caps similar to CSX-2345?

[1985 CCX]

I would get a couple cans like this and call it a day.

Easy
Metal and cheap

https://www.thecarycompany.com/f-sty...20group%20%231

[seatra]

Originally Posted by Tommy

In general a PCV system serves three purposes. It burns vapors that would otherwise escape into the air. It can reduce crankcase pressure to lessen oil leaks at seals and enhance engine performance slightly. And it can reduce contaminates inside the crankcase allowing oil to remain cleaner longer.

The Cobra I once owned was built for street and track use with no PCV and a catch can plumbed to the closed valve covers. I changed the oil and emptied the small amount in the catch can before each track event. Other than negligible damage that may have been done to the environment, I saw no disadvantage to that system. Had it been a car that saw 15,000 miles per year, my answer may have been different.

Tommy, Appreciate the feedback. My plan is to build a car for street and track use too. If I go with the Webers then PCV won’t/can't be on mine either. Don’t mind the more frequent oil changes unless it’s my RAM pickup.

[seatra]

Originally Posted by 1985 CCX

I would get a couple cans like this and call it a day.

Easy
Metal and cheap

https://www.thecarycompany.com/f-sty...20group%20%231

I like it, simple yet elegant!

[1795]

Just make sure that the catch can has a breather on it. It can be as simple as punching holes and putting some filter paper over the top of them, but it needs to breathe.

Jim

[6TNCRZY]

A PCV only works when the manifold has vacuum, not much value on a race car.

[KarlzEE Bebout]

My manifold for my Webers does have a plenum chamber on the underside with two threaded pipe plugs in between the carbs. I don't know what brand it is and don't remember seeing a name. I put a 90° fitting in one of those, ran a hose with an inline PCV valve to a tee fitting with hoses going to both valve cover breathers. Works pretty well but I do still get some blow by with some higher RPM spirited driving. Might have something to do with the engine getting close to 90,000 miles

[Tommy]

Originally Posted by KarlzEE Bebout

My manifold for my Webers does have a plenum chamber on the underside with two threaded pipe plugs in between the carbs. I don't know what brand it is and don't remember seeing a name. I put a 90° fitting in one of those, ran a hose with an inline PCV valve to a tee fitting with hoses going to both valve cover breathers. Works pretty well but I do still get some blow by with some higher RPM spirited driving. Might have something to do with the engine getting close to 90,000 miles

Perhaps I don't understand your description, but it sounds like the vacuum from your plenum is pulling through the PCV valve to two breathers. If so, it seems to me that at higher vacuum levels the plenum is likely pulling in outside air more than crankcase vapors. I used the more common arrangement of having the PCV pull from one valve cover with the breather on the other. At low RPM / high vacuum the system pulls crankcase vapors in through the PCV valve while outside air enters through the breather to equalize the pressure. At high RPM with high crankcase pressures, the PCV pulls in as much as it can and excess pressure is vented out through the one breather.

[KarlzEE Bebout]

Tommy, you've got me scratching my head now. Maybe I'll block off one of the valve cover vent lines to see if maybe that will be more effective. Thanks for the tip. K.

[seatra]

Originally Posted by Tommy

Perhaps I don't understand your description, but it sounds like the vacuum from your plenum is pulling through the PCV valve to two breathers. If so, it seems to me that at higher vacuum levels the plenum is likely pulling in outside air more than crankcase vapors. I used the more common arrangement of having the PCV pull from one valve cover with the breather on the other. At low RPM / high vacuum the system pulls crankcase vapors in through the PCV valve while outside air enters through the breather to equalize the pressure. At high RPM with high crankcase pressures, the PCV pulls in as much as it can and excess pressure is vented out through the one breather.

I didn’t stay at a Holiday Inn Express last night but that’s how I’ve always understood it too. The PCV valve allows vapor flow from the high pressure (valve cover/engine crankcase side) to the low pressure (intake/vac source side). I don’t think the PCV valve totally shuts off flow, it just regulates it. Low RPM/high vacuum pulls the PCV valve disc up, against spring pressure, and restricts gas flow through the valve body. When vacuum reduces during higher RPM, the valve body spring pressure overcomes the vacuum source and pushes the valve disc back down to allow more flow through the valve body and into the vacuum source. Of course these crankcase vapors would flow much better with some sort of ventilation, and like Tommy pointed out, that is usually done on the opposite valve cover via a vent.

[twobjshelbys]

This is a different flavor of the breather/PCV/catch can discussion that has gone on many times here...

In Ford engines one side will be mild vacuum and the other side positive pressure outbound. The pressure side is the side on which the PCV system resides to direct the "exhaust" back into the air breather assembly (somewhere) where it goes back into the engine.

Catch cans are, with rare exceptions, just income to the producer of the part. They serve no useful purpose. The amount of oil "blow by" captured is drops per 100 miles and will do nothing to reduce octane. If they were an important part of the EPA gas rating of engines trust me they'd be there from the factory.

The joining of the two sided nature of the covers is why there is no value in having two catch cans.

With two exceptions...

First, racing and continued operation at high revs does produce some blow by. The amount is still inconsequential to engine operations.

Second, if you have excessive blow by, and if you have virtually any in the vacuum side, then that is the sign of a much larger engine problem than a catch can can solve. Especially if you have a naturally aspirated engine.

I understand that some recent model year GT500s have catch cans as do (unconfirmed) the higher end versions of the Challenger, but noone can verify that they collect other than miniscule amounts. Note both are supercharged applications.

My Kenne Bell equipped Shelby GT had a catch can that never saw any oil and it wasn't because I drove it like an old lady. The later Ford/Whipple version did not include one.

[1795]

Unless you are racing there really is no need for a catch can. Most, if not all, race sanctioning bodies require a catch can for any part of the car that has fluid in it to prevent spills on the track. If you are using one to replicate a race version of a car, then go ahead. If you think you need one, probably not. On a race ar you will be running the engine at high rpm's for extended periods and could possibly have some oil in the catch can, on the street that is not likely.