Let's crank it up.

[james]

Do any of you guys use a crankcase evacuation system (what kind) or valve cover breathers, (what kind)? Which would you use and what are the positive and negatives of each? Or can you use both? Just asking? Thanks!

[blykins]

I use valve cover breathers on about everything as I'm not a PCV valve fan.   

Header and pan vac systems are a little more involved as they need hardware installed into the headers, and you still need either functional breathers on the valve covers with nipples on them for the hoses, or you need a fitting installed somewhere on the engine to pull vacuum on....a fuel pump block off plate, etc.

[My427stang]

Depends on use, on a race car, PCVs do nothing as vacuum is zero.  On a street car, they do great at part throttle and the best way is to use a breather to the air cleaner to take over at WOT when there is no vacuum.  Many can do fine with just breathers

Keep in mind though, any of these setups assume a motor with decent ring seal.  If you have a ton of blow by, PCVs and air cleaners pull oil, and breathers get messy, neither of which is good. 

I have built a few pan evac setups using exhaust and they work great, but only for open header racers.  Brent and Jay have a lot of vacuum pump experience and they can make power for a racer, but I have never used one.

[Barry_R]

On a race car the vacuum pump is absolutely the way to go - expensive and complex, but I have seen repeated double digit power gains with no other changes. 

The header evac deal is much less expensive and will still give an extra bit of power - I seem to recall a  consistant five or ten.

On a serious hot rod or mild racer ( or where evac systems are not permitted by rules) a breather in each cover is the best thing to do.  You need to provide an exit for crankcase blow-by gasses to escape from.

On a mainly street deal I will agree with Ross - the PCV does a very good job of keeping leaks to a minimum and keeping the engine compartment clean.  You do need to provide an open breather in the system because - as he mentioned - flow through the PCV is essentially zero at WOT where blow by is at its highest.

[BattlestarGalactic]

All my junk, including the race car have PCV.  Guess I'm not up to par?  But it works well enough for me 

[unclewill]

I use a PCV valve and an open element breather/oil fill cap on the drivers side valve cover for my street car.  I have found that straight breathers smell bad inside the car and emit a fine mist of oil which can make a mess out of the engine compartment.

[TJ]

Back when I thought I needed a PCV valve, I fooled with a PCV setup and baffles in the valve covers for quite a while and found out those adjustable pcv valves do reduce oil sucking if you ever notice that as a problem. 

I used to have a jasper 390 that I had a pcv valve on one valve cover and breather on the opposite valve cover.  Engine blew by so much I kept a sock on the breather to keep oil off my headers.  Engine I have now doesn't seem to blow by (that I can notice) so I have 2 breathers on each valve cover and they stay dry which is note worthy since most of my miles are freeway at around 3000 rpms.  Just make sure engine reaches at least 180F to drive moisture out of the oil.

[jholmes217]

Back when I thought I needed a PCV valve, I fooled with a PCV setup and baffles in the valve covers for quite a while and found out those adjustable pcv valves do reduce oil sucking if you ever notice that as a problem. 

I used to have a jasper 390 that I had a pcv valve on one valve cover and breather on the opposite valve cover.  Engine blew by so much I kept a sock on the breather to keep oil off my headers.  Engine I have now doesn't seem to blow by (that I can notice) so I have 2 breathers on each valve cover and they stay dry which is note worthy since most of my miles are freeway at around 3000 rpms.  Just make sure engine reaches at least 180F to drive moisture out of the oil.

Adjustable PCV valves?  Can you post a link to the company?  Sounds interesting.

[unclewill]

The most expensive PCV valve on Rock Auto for a 390 is $2.14 -  the cheapest is $.51!!  You can restrict the vacuum line to adjust it if necessary but spending any more money on one seems like a waste to me.

[TJ]

Should be able to find it if you google ME Wagner PCV valve.  They're $129 and like unclewill implied, there's more than one way to skin a cat.  If you're going to use a PCV valve on a custom FE, I think you'll need some way to adjust it...restrict the hose, fancy valve, something.

[machoneman]

Get a PCV valve for a Boss 302! I've fooled with this issue a lot and the Boss unit has the lowest spring tension and has worked well on many a hot-rodded engine that users have tried it on.

[CaptCobrajet]

I'm a big fan of a properly designed PCV, and other means of creating negative pressure in the crankcase.  As Barry said, vacuum pumps always boost power through better ring seal......always.  On race cars where vac pumps are not permitted, the pan evacuation hoses to the headers are definitely worth something.  It is very important to monitor the  check valves to make sure they are checking properly.  They will blow out periodically, and can pressurize the crankcase if the valves blow out.

In some cases, like Stock Eliminator drag engines, neither vac  pumps nor pan evacs are legal.  Sealed PCV systems absolutely DO help Stockers.  We adjust the spring tension in the inline check valves, and plug directly into the manifold, with no other venting.  Anytime there is vacuum, and with special check valves in play, it makes negative pressure.   The vacuum will last usually through the middle of second gear if you have good ring seal......it then eventually goes to zero, but then in high gear, when rules limit carb size, the vacuum returns.  I wouldn't run a Stocker without PCV.

On street pcv systems, I think they are very beneficial.  Most people get it half-right, and then it does nothing.  The PCV valve should connect to manifold vacuum.  The other "breather" should have a much lighter inline check valve(lighter than the pcv), turned the opposite direction in terms of flow, and connected to the AIR CLEANER.  Doing this will check it off and the pcv valve will evacuate at idle and part-throttle, without just pulling air and "leaking" from an open breather on the other side.  At wide open throttle, the pcv valve will close, but the negative pressure inside the air breather above the carb or throttle body will pull on the lighter check valve in the other valve cover and insure no positive pressure at WOT.  Back off the throttle, and the breather will check off and your pcv will open.....back to vacuum again.  If the system is not SEALED and properly "checked" on both sides, the pcv valve really won't do much in terms of benefits to engine performance.  A pcv valve and an opposite open breather will reduce the stink as was mentioned above, but will not create negative crankcase pressure.  The '70s Ford pcv was a wonderful setup.  The filter in the air cleaner had enough resistance to allow the pcv to work, and vented enough at WOT, which was sporadic, to prevent crankcase pressure during those events.

[scott foxwell]

Vacuum pumps do more than improve ring seal. They also improve windage issues because of reduced atmosphere in the crank case. Any skirted block will benefit more from a vac pump.
As already said, the crankcase needs venting. All engines have some level of blow by and will pressurize the crankcase if not vented. More HP, more rpm, forced induction...means more ventilation.
The PCV valve was designed for nothing more than getting caustic fumes out of the crank case. It was learned long ago that when oil vapor is mixed with combustion blow-by inside the crankcase it becomes corrosive to the bearings. It's for this reason that oil contains calcium...to try and reduce the acidity in that condition. In the beginning, there were road draft tubes that helped pull those corrosive fumes from the crankcase while going down the road, but it was soon realized that they did nothing when the car was at a stop. Enter- the PCV valve. The thing is, under acceleration or low vacuum conditions, the PCV valve does nothing to help "vent" the crank case when it needs it the most.
On performance engines I highly recommend more than one breather. One breather and a PCV valve, IMO, are not enough crankcase ventilation. ONe nice thing about the FE is the provision at the back of the intake for a PCV valve. If you feel the need to run one, then I'd run it there, and run two breathers; one in each valve cover.
Vacuum pumps are a little expensive but nothing could be simpler. They take less than 2hp to run at rpm and ANY engine will benefit from one. You could run a smog pump in it's stock location and bracketry and pull enough vacuum to be useful. Header evac systems have been shown to pull some significant vacuum depending on how they're designed. One thing to remember about trying to create negative pressure in the crankcase...the engine has to be sealed as well as possible. No breathers. I did an old trick to one of my small blocks once...I used the mechanical fuel pump as a vac pump and plumbed it into the side of the front cover. Never had a way of measuring anything but I could definitely tell when I hooked it up.
Vac pump is probably one of the best investments someone could make in their performance engine. I've seen 36 hp on one engine, and over 40 on another, verified on the dyno because of the vacuum pump.

[CaptCobrajet]

The back of the manifold is a good place to suck oil.  Two well-baffled valve covers are the ticket.   On dual carb FEs with baldy covers, I plumb the pcv into the oil fill tube at the front of the manifold, much like Ford did with the 5.0 302s, above the baffle, and connect the air cleaner/checked line to the back of the manifold.  It needs a sealed oil cap.....we weld the neck off of a '90s model 302 valve cover right onto the FE oil fill tube.  In a sealed/checked system, the rear intake basket deal will pull oil into the manifold if you hook manifold vacuum to there.

[james]

Do any of you guys use a crankcase evacuation system (what kind) or valve cover breathers, (what kind)? Which would you use and what are the positive and negatives of each? Or can you use both? Just asking? Thanks!

A big thank you for all the great answers.