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Do I have to run a pcv

Posted By: HEMIDOG 70

Do I have to run a pcv - 10/18/12 01:31 AM

I have just started driving my Challenger. It has a 528 hemi. Right now I have a moroso breather with the nipple for a hose on each valve cover no hoses hooked up yet. Can I just t these breathers to the nipple on the air cleaner or is a pvc to the carb a must have? I have about 100 street miles on the engine and no issues I can see. The valve covers are the Barton Stage v cast covers.
Posted By: Supercuda

Re: Do I have to run a pcv - 10/18/12 01:42 AM

you don't "have to" but you ought to. Helps keep the engine clean, inside and out.
Posted By: JohnRR

Re: Do I have to run a pcv - 10/18/12 03:48 AM

Quote:

you don't "have to" but you ought to. Helps keep the engine clean, inside and out.



Posted By: 70duster340

Re: Do I have to run a pcv - 10/18/12 04:11 AM

When I first bought my Duster, the previous owner had just a breather installed on the valve covers of the 340. It had a constant oil film on the valve cover. It will help keep the engine clean.
Posted By: 79powerwagon

Re: Do I have to run a pcv - 10/18/12 10:44 AM

Why would you not run a PCV?
Posted By: therocks

Re: Do I have to run a pcv - 10/18/12 11:08 AM

My 65 built 440 runs just 2 breathers.My kids 62 300 413 with 50K OE miles runs 2 also.Neither has any problems with pressure or oil film.Mine runs an M1 intake with Dominator and has no provisions for vacuum.When we put the headers on the 300 it eliminated the draft tube.Both have run like that for over 10 years.Rocky
Posted By: 1BAD68

Re: Do I have to run a pcv - 10/18/12 02:07 PM

Mine has a PCV on one cover and a breather on the other, is this right?
Posted By: JohnRR

Re: Do I have to run a pcv - 10/18/12 04:08 PM

Quote:

Mine has a PCV on one cover and a breather on the other, is this right?



yes
Posted By: bonefish

Re: Do I have to run a pcv - 10/18/12 04:13 PM

Quote:

My 65 built 440 runs just 2 breathers.My kids 62 300 413 with 50K OE miles runs 2 also.Neither has any problems with pressure or oil film.Mine runs an M1 intake with Dominator and has no provisions for vacuum.When we put the headers on the 300 it eliminated the draft tube.Both have run like that for over 10 years.Rocky

same here on my 496,if i beat on it real hard i will get a little oil seepage from the dipstick.
Posted By: Challenger 1

Re: Do I have to run a pcv - 10/18/12 04:20 PM

Quote:

Quote:

My 65 built 440 runs just 2 breathers.My kids 62 300 413 with 50K OE miles runs 2 also.Neither has any problems with pressure or oil film.Mine runs an M1 intake with Dominator and has no provisions for vacuum.When we put the headers on the 300 it eliminated the draft tube.Both have run like that for over 10 years.Rocky

same here on my 496,if i beat on it real hard i will get a little oil seepage from the dipstick.



Without a PVC valve, you are putting more pressure on the seals. Do you want oil leaks? Why not run one? Because you don't understand what they do?
Posted By: LaRoy Engines

Re: Do I have to run a pcv - 10/18/12 04:43 PM

The pcv is an emissions device that routes the oil vapors, produced by the engines internals, into your cylinders to be burned. Push all the oil into the cylinders that you want, it is however a very low octane fuel.
Posted By: az426john

Re: Do I have to run a pcv - 10/18/12 06:11 PM

Back in the day, before there were PCV valves, there were road draft tubes to relieve pressure build up. These were cut on an angle and when you were driving created a low pressure stream that would remove the vapors and the built up pressure.
Posted By: JohnRR

Re: Do I have to run a pcv - 10/18/12 06:30 PM

Quote:

Back in the day, before there were PCV valves, there were road draft tubes to relieve pressure build up. These were cut on an angle and when you were driving created a low pressure stream that would remove the vapors and the built up pressure.



Similar to evac tubes in headers ?

Where would one have been on a big block , or smallblock for that matter , Chrysler ? I remember seeing one on the 56 Chevy I owned with a 6 banger ...

I can see not using a PCV on a race engine , street engine I would think it wouldn't really hurt ...
Posted By: therocks

Re: Do I have to run a pcv - 10/18/12 07:49 PM

BBs were on the pass side valve cover.I had quite a few.My kids was in the same place.He runs 2 K&N screen breathers and I run 2 Moroso breathers.Neither leaks.His 300 probally got more street miles in a year than most cars here get in 10.My 440 is pretty much a race motor driven on the street.Ive driven it quite a bit and no problems.Besides Im not goimg to drill a new intake just to install a PCV.Its sees 6 to 7 K revs regularly.Rocky
Posted By: Cab_Burge

Re: Do I have to run a pcv - 10/18/12 08:11 PM

I run two PCV ,one in each valve cover, in my 518 C.I. pump gas stroker motor. I used a vacume T off the back of the intake that I drilled and tapped for a pipe thread and used a brass pipe nipple to hook the vacume hose to the T to I also run two breather caps, one in each cover. The PCV helps suck any condensation out of the motor once it gets up to temps as well as sucking any blowby fumes into the intake manifold, much better to burn them rascals up than to let them sit in the motor and cause acids mixing the water and oil together Besides adding the PCV opens up some more control vaume leaks, making the motor idle better with big cams
Posted By: Ramrod39

Re: Do I have to run a pcv - 10/18/12 10:58 PM

Do you have to re-jet the carb when you add a PCV valve? Or is the amount of air drawn into the the intake at idle so low it is a non-factor? What about at open throttle?
Posted By: dogdays

Re: Do I have to run a pcv - 10/18/12 11:08 PM

Generally the PCV is closed at idle, the high vacuum sucks it closed. Then at some point as vacuum drops, it opens up.
Now I'm not saying that there's no leakage, but if the PCV is stuck open it's hard to get a car to idle.
And yes, technically the oil vapors lower the octane rating of the mixture. It seems however, that the benefit of running a little vacuum or at least no positive pressure in the crankcase has more benefit.

My Poly 318 was leaking oil from every gasket. I found the hose to the PCV valve was collapsed internally. Replacing the hose cured 90% of the oil leaks.
R.
Posted By: Ramrod39

Re: Do I have to run a pcv - 10/18/12 11:23 PM

Is a generic Auto Zone PCV valve OK? Brand recommendations?

What kind of hose?
Posted By: Cab_Burge

Re: Do I have to run a pcv - 10/19/12 02:51 AM

Quote:

Generally the PCV is closed at idle, the high vacuum sucks it closed. Then at some point as vacuum drops, it opens up.
Now I'm not saying that there's no leakage, but if the PCV is stuck open it's hard to get a car to idle.
And yes, technically the oil vapors lower the octane rating of the mixture. It seems however, that the benefit of running a little vacuum or at least no positive pressure in the crankcase has more benefit.

My Poly 318 was leaking oil from every gasket. I found the hose to the PCV valve was collapsed internally. Replacing the hose cured 90% of the oil leaks.
R.

You have the PCV operation theory backwards, it is open at high vacume and the spring inside closes it at WOT or when the motor is not running, if it is hook up correctly If you hook it up backwards it will work backwards
Posted By: Ramrod39

Re: Do I have to run a pcv - 10/19/12 05:03 AM

Cab - I think you have the vacuum/valve open/valve closed thing bass-ackwards....
Posted By: 1BAD68

Re: Do I have to run a pcv - 10/19/12 12:32 PM

I'm pretty sure it's closed at idle, otherwise it would act like a big vacuum leak.
Posted By: Mr T2U

Re: Do I have to run a pcv - 10/19/12 01:36 PM

i have a 572 hemi.
i use cast breathers bolted to cast mopar valve covers. i have a single plane intake and the valve covers really aren't set up for pcv valves, so using a pcv system gets complicated.
i run a 10 or 12an, can't remember which, braided line line from the breather to the bottom of the air cleaner. seems to work ok.
if i used baffle in the valve cover i would get less oil thru the breathers. the only problem is there isn't enough room in the valve cover for that.

Attached picture 7427112-roadrunner005.JPG
Posted By: Cab_Burge

Re: Do I have to run a pcv - 10/19/12 05:35 PM

Quote:

I'm pretty sure it's closed at idle, otherwise it would act like a big vacuum leak.

That is real easy to check, start your motor up, pull the PCV out and put your finger over the hole in the bottom of the PCV and let us know if your motor speeds up or slows down blocking the PCV Let us know your results
Posted By: 1BAD68

Re: Do I have to run a pcv - 10/19/12 05:59 PM

Edit:
At idle the PCV is forced open from vacuum.
At high rpm's, the PCV closes.
Still don't know if it's a spring that closes it?
Posted By: skicker

Re: Do I have to run a pcv - 10/19/12 06:24 PM

I put about 5,ooo miles or so on my 383 and always had a oil pushing out the breather and trying to leak around the ends of the intake. I'm running an old set of MT valve covers that had no hole for a pcv. After pushing a valve cover gasket out a few weeks back I drilled the v/c for a pcv. END OF PROBLEMS! I never ran one before on aftermarket v/c's but from now on I'm not running without one.

Yeh Mike...I know if I would've listened to you....
Posted By: therocks

Re: Do I have to run a pcv - 10/19/12 07:43 PM

They suck at idle.Pull one and see.As for pushing out a cover gasket you need a rebuild or better gaskets.Our cars get the h--l beat on them and I know the 62 with 50K has never been reringed etc.No problems ever.Rocky
Posted By: RobX4406

Re: Do I have to run a pcv - 10/19/12 08:03 PM

Quote:

Quote:

I'm pretty sure it's closed at idle, otherwise it would act like a big vacuum leak.

That is real easy to check, start your motor up, pull the PCV out and put your finger over the hole in the bottom of the PCV and let us know if your motor speeds up or slows down blocking the PCV Let us know your results



Of course it's going to speed up. It's a vacuum leak at idle. Most of them have an orfice to leak at idle regardless of vacuum.

Pull the pcv from cover, hook up a vacuum gauge to another port and observe what the gauge does when the pcv is attached, attached and covered and completely unplugged. Those observations should get you in the area of how it works and whether it's closed or open at high/idle vacuum situations.
Posted By: Supercuda

Re: Do I have to run a pcv - 10/19/12 11:57 PM

PCV Valves are open at idle. One set of ring seal is to idle the engine, pull the breather and see if a piece of paper will get sucked down in the open hole by vacuum (obviously you have the PCV in place for this test).

If it doesn't get pulled down and seal the hole, or worse yet you see exhaust pulsing out the hole you have ring seal issues.
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