Do we need a PCV System?

[moparmaniac59]

I run 2 vents filters on my valve covers (They have a removable cleanable filter in the metal housing), but one of the filters has a barbed fitting which I run a vacuum hose to the adapter plate my carb mounts on for negative pressure. I just don't have the actual PCV valve (which has a check feature). See the attached pic for the type filter I use. (The vacuum hose is not attached in the picture). This setup seems to work well with my engine. 


                                                                             Matt B.

[jhaag]

Think it through. If you connect a vacuum hose to your valve cover, you need a pcv valve in the system in case of an engine backfire. You don't want to blow the pan off. If you are sucking oil out of your valve covers you need to put a baffle under it or move it to a different location. You should have only a very slight mist entering your intake which is in turn sucked back into the engine and burned, creating no ill affects. All you need is a breather on 1 side and pcv connected to the carb base, on the other. This creates some negative pressure and source for clean air. Negative pressure helps horsepower, ring seal. blowby, etc. If you have ever looked at pro stock drag racing engine technology, you will see they actually use vacuum pumps to create negative crankcase pressure. So the answer to the original question is yes a properly designed and connected pcv system, while not absolutely necessary is far better than 3 or 4 breathers open to the atmosphere.

[cudabob496]

Think it through. If you connect a vacuum hose to your valve cover, you need a pcv valve in the system in case of an engine backfire. You don't want to blow the pan off. If you are sucking oil out of your valve covers you need to put a baffle under it or move it to a different location. You should have only a very slight mist entering your intake which is in turn sucked back into the engine and burned, creating no ill affects. All you need is a breather on 1 side and pcv connected to the carb base, on the other. This creates some negative pressure and source for clean air. Negative pressure helps horsepower, ring seal. blowby, etc. If you have ever looked at pro stock drag racing engine technology, you will see they actually use vacuum pumps to create negative crankcase pressure. So the answer to the original question is yes a properly designed and connected pcv system, while not absolutely necessary is far better than 3 or 4 breathers open to the atmosphere.

I considered a vacuum pump, but was told you have to have special rings for it to be effective.
Not sure how a back fire could blow pan off, if valve covers vented. Will have to think about that one.

[7212Mopar]

I think this would be a good read, kind of long but informative.

 http://www.shophemi.com/images/media/p-2273-arrington_ccv_bible.pdf

[jhaag]

Excellent read 7212mopar! Bob, the blow the pan off comment was for moparmaniac. He said he is not using a pcv, which is a checkvalve. If you have an unrestricted path to gasses in the crankcase a backfire could ignite them. Highly unlikely, but possible.

[blown motor]

I'm confused. How can your intake manifold vacuum be higher at idle? A higher RPM would require more CFM to be drawn in so wouldn't that create more vacuum in the manifold?

[Chryco Psycho]

at idle the htrottle plates are closed but the enigne is trying to draw in air with no source available so the vacuum is high , at wide open throttle the engine + rpm is drawing in a lot more air but the throttle is wide open so the air supply is easy to access = lower vacuum

[cudabob496]

I think this would be a good read, kind of long but informative.

 http://www.shophemi.com/images/media/p-2273-arrington_ccv_bible.pdf

dang, thats a good article. OK, I'll keep the PCV system, and just build a good oil separator.
Only real comment I have is that it mentions you keep bad crankcase air from going into the environment. True,
but on the other hand, I have 600 hp worth exhaust coming out of a dual 3 inch exhaust system, so a few
crankcase fumes are insignificant, with respect to that!

[moparmaniac59]

That was a very detailed in-depth article. I used to run lines from the valve covers to anti-backfire valves welded into bungs on my headers. Pretty much a race set-up suited for straight pipes. I have a catch can, but need another to run a double catch-can setup with no PCV valve as shown in the article. A good catch can is costly. Thanks for sharing the article! 

                                                                           Matt B.

[cudabob496]

That was a very detailed in-depth article. I used to run lines from the valve covers to anti-backfire valves welded into bungs on my headers. Pretty much a race set-up suited for straight pipes. I have a catch can, but need another to run a double catch-can setup with no PCV valve as shown in the article. A good catch can is costly. Thanks for sharing the article! 

                                                                           Matt B.

I'm making a catchcan out of 1.5 inch PVC black pipe, 6 inch long, two end caps, stuff it with stainless steel wool (can get in the cleaning section of ACE Hardware). A 3/8 NPT going in, and one going out, and a drain valve on bottom.

[Aussie Challenger]

PCV's are a must, I had a motor that drank more oil than fuel, so I then removed the R/C and made special baffle which couldn't collect oil and in fact directed oil away but still allowed vapor to pass up the tube and be burnt. Hard to explain what I did but making the baffle considerably larger than just covering the hole really helps.

[inviolet]

Great article. I'm looking into this style Catch Can. Maybe I can mount it off the motor somehow. Anyone else have any ideas?

[burdar]

I just bought a $35 aluminum can off of Amazon.  It's pretty big...bigger then I thought it was going to be.  It's empty inside but I'll add some steel wool or something to filter out the oil vapor.  I'm going to mount in on the PS inner fender right next to the firewall.

It looks like I purchased the same breathers as "moparmaniac59".  The breather with the nipple has a PCV valve INSIDE of it.  You don't need another one.  The valve is held in with a snap ring on the bottom side. 

[HP_Cuda]

Anyone know an inline PCV valve that would work on a big block setup?

It seems the Standard motor V165 would work but would need some massaging.

Think I'm going to wait to see what vacuum this motor will be pulling before finding a PCV valve.

[inviolet]

I'm think it maybe more effective to just eliminate the PVC valve, and just plum off the valve cover into a catch can than from the catch can to the stock air filter bong before the air cleaner, and leave the other valve cover with an open air breather. If the engine back fires the air filter will be in the way.

Sounds good?