To PCV or not?

[440]

I currently have a 440 6 Pack and at the moment has two breathers. One of them is a billet breather and since I hate it I'm looking to replace it but that got me to thinking, should I replace it with a PCV valve or a plain ol' chrome breather, or non PCV breather with tube? PCV equipped engines tend to stay a bit cleaner inside but many also recommend to ditch them due to ingesting oil through the air cleaner.

Thoughts? Opinions?

[John_Kunkel]

When installing a PCV in a valve cover, it's essential that the opening in the valve cover has a baffle inside to prevent oil from being ingested into the engine.

I can't picture a PCV system that would ingest oil "through the air cleaner"; normally, only fresh air is drawn through the air cleaner, drawn through the engine internals, and exits through the PCV.

[440]

Yes most valve covers should have a baffle around the breather to prevent oil sloshing out. The PCV port is also normally under the throttle plates but non PCV breathers hook up to fittings on the air cleaner. No matter what you will still suck oil vapor etc into the intake unless you use a catch can.

I'm just asking is it wise to install a PCV back in or just stick with two breathers, or split the difference and use a normal breather with tube to air filter assembly?

[RallyeMike]

There is a down side to having crank pressure vented into your shiny engine bay. There is no downside to sending it back to be combusted.

[Bronzedodge]

Right - what Mike said above.  As long as it's right, there is no downside to PCV.  Your rings might seal better eventually.

[c00nhunterjoe]

With the majority of our engines having lots of overlap, there isnt much engine vaccum to work with so the gains from pcv will be negligible at best. But it is still better then straight breathers. If you want max performance- invest in a vaccum pump. 15-20 hp gain easily by running 8" on the crankcase in a mopar

[440]

Seriously, 15 - 20 hp just from drawing vacuum on the engine?

I already have a vacuum pump set up to run the power booster so tapping off of that shouldn't be too hard.

I decided to just run a hose from the breather to air cleaner assembly so it is at least recirculating, but now I'm interested in the vac set up as the pump is already there (electric).

[c00nhunterjoe]

I doubt the pump you have is capable of what is needed, or would last. You will also need a suitable filter system because it will draw oil in.

[440]

Maybe, but it runs the power brakes 100% of the time.

Yes a catch can set up is a must to seperate the oil, but I'm not sure I want that on my car, maybe for a race car or hot street machine.

I had another look and the problem with the 6 pack air cleaner is that there are no "sealed" ports to connect a breather to. There is one but it's outside the element which is kind of useless.

[green69rt]

I'm trying to remember the arrangements I've seen on cars.   If you have two breathers now, and replace one with a PCV valve that goes to a vacuum port then what you will have is a system that will "sweep" vapors from the crankcase.  I thought this was to remove and water from the crank case (causing oil foam) and to remove gasoline vapor (prevents oil dilution).   You probably won't be removing much oil vapor.  But yes, the PCV side does need a baffle of some kind (usually mounted inside the valve cover) to keep oil drops out of the carb.

The arrangement that I remember had one breather use a rubber hose connected to the underside of the air filter so it would draw filtered air into the engine.  The PCV valve was connected to a vacuum port at the bottom of the carb to provide the suction.  Because this is another air source for combustion, the carb has to be jetted accordingly but because it's a small stream it might not need any change in jetting but it doesn't hurt to check.

Never thought that drawing a vacuum on the crankcase would add horsepower??

[c00nhunterjoe]

Maybe, but it runs the power brakes 100% of the time.

Yes a catch can set up is a must to seperate the oil, but I'm not sure I want that on my car, maybe for a race car or hot street machine.

I had another look and the problem with the 6 pack air cleaner is that there are no "sealed" ports to connect a breather to. There is one but it's outside the element which is kind of useless.

Which i why i said "if you are looking for max performance..."

[440]

PCV is probably the best option then. Looks like the power brake/pcv port is on the base of the center carb which in my case is free to use as it's plugged. I'd like to take a vacuum reading off it to see if the electric pump is necessary or not.

I'll probably have to do the PCV when I get the car dyno tuned as I still have some Quick Fuel jetted metering plates to go in the outboard carbs.

[c00nhunterjoe]

There are different valves available depending on what cam you have installed. Vaccum plays a big role here of course.

[440]

I wouldn't have a clue what's in it at the moment but when I bought the car the guy said it had a Mopar purple cam in it. It could be anything but I assume it's low on vacuum due to the auxiliary vac pump.

I tore the car apart before I took any readings so I'll have to wait till the dash is back in.

[c00nhunterjoe]

Probably going to have 8-10" with a purple cam.

[tsmithae]

I just went through the hassle of trying to find something for my Weiand finned aluminum valve covers.  I had an impossible time finding a PCV that fit.  Turns out Scott Drake has a grommet (C7AZ6892) that  is made for a Ford application but worked great for me.   

[metallicareload99]

The best part of PCV for me is if there is a leak, it will be air leaking into your engine, instead of oil leaking out. At least in theory

... can't picture a PCV system that would ingest oil "through the air cleaner"; normally, only fresh air is drawn through the air cleaner, drawn through the engine internals, and exits through the PCV.

Do you think it's possible on a engine that is in "good" condition would have enough blow-by that flow reverses and crank case pressure vents into the air cleaner @ higher RPM?

With the majority of our engines having lots of overlap, there isnt much engine vaccum to work with so the gains from pcv will be negligible at best. But it is still better then straight breathers. If you want max performance- invest in a vaccum pump. 15-20 hp gain easily by running 8" on the crankcase in a mopar

I've been thinking about adding one, but my car is mainly street/daily driver.  How many miles a year do you put on that, how long can you go before needing to rebuild it?

I've thought about using a grommet that doesn't have the hole cut out yet, put a very small hole in it to reduce the amount of air available on the breather end of the PCV system.  The idea being that the crankcase will then be under a constant vacuum.  My concern would be that at high RPM the PCV valve wouldn't be able to flow enough to maintain the vacuum, nor would the breather allow enough to escape, the result being crankcase pressure

[c00nhunterjoe]

With the pistons moving up and down, a tiny hole in the breather vs the correct size hole would cause damage to the rings.