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PCV - Yes, No for Street

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Discussion starter · #21 ·
vonzipper396 said:
The problem with a pcv valve on a big 540 with 700+hp is at high rpms you will generate more base pressure than a little pcv valve can flow, resulting in the dipstick pushing out and the pcv pushing out during full throttle blasts.if you only street drive and baby it around you might be ok.I went to a breather in both covers and am still getting oil mist everywhere on my 525 at 7200rpm so the next step is either a pan evac setup or vacuum pump.
Click to expand...
I was told this also from Patrick (Pro Systems). Told my builder this and
he disagrees. Said he never seen this happen and just had motor dyno'd
with 6 pulls (710hp, 685tq) and had no visable signs of this happening.
What is pan evac? Was told not to waste $ on vacuum pump for street
car (something to do with lack of oil maybe, do not remember). Other
option w/out PCV is 2 breathers and breather tank which should cut
down on oil mist in engine compartment. My concern with breather
way is been hearing without PCV on street car can due harm or some
kind of issues arise. Would like to go the 2 breather way myself and
use a breather tank to absorb some of oil mist which may come from
vc breathers which save me $. Once again, is there something that
could be harmful to my str driven car not using PCV. Also, if it may
matter, car is driven maybe 60 miles a week. Thanks! Bob
 
#23 ·
Ramrodd 69 said:
I was told this also from Patrick (Pro Systems). Told my builder this and
he disagrees. Said he never seen this happen and just had motor dyno'd
with 6 pulls (710hp, 685tq) and had no visable signs of this happening.
What is pan evac? Was told not to waste $ on vacuum pump for street
car (something to do with lack of oil maybe, do not remember). Other
option w/out PCV is 2 breathers and breather tank which should cut
down on oil mist in engine compartment. My concern with breather
way is been hearing without PCV on street car can due harm or some
kind of issues arise. Would like to go the 2 breather way myself and
use a breather tank to absorb some of oil mist which may come from
vc breathers which save me $. Once again, is there something that
could be harmful to my str driven car not using PCV. Also, if it may
matter, car is driven maybe 60 miles a week. Thanks! Bob
Click to expand...
I personally have the evac system on my motor with one breather to atmosphere. Works great the only issue is that, any vacuum I would be applying to my rings is negated by the open element breather. The best way to get around this is a check valve, which maybe someday I will get around to putting one on the atmosphere vent.

The evac system to your exhaust is a great setup but is only sufficient above about 3k and meant for drag motors. When added to an open vent works awesome. Simply speaking though it doesn't matter if it is venting to atmosphere or being pulled by vacuum from the intake system. Typically I disconnect the intake system, the only reason we do this today is emissions. The gasses coming out of the crank case are riddled with hydrocarbons. Although I will disagree on an engine producing more blow by than the PCV system can handle, all motors today under heavy loads see right around atmospheric and usually drop into a vacuum situation because the PCV is working well. PCV IS A MUST or else you will blow out seals, the only reason for the PCV is because you can significantly pressurize the crank case, i have seen one hit over 25 kpa and blow an oil pan gasket out. If its vented to atmosphere perfect, I hate putting it in my intake tract because the oil it will pull in wreaks havoc. You will get nasty intake valves, carbon and gunk build up in the runners and so on. If i run this to my exhaust who cares.
 
#24 ·
Radcannon said:
I personally have the evac system on my motor with one breather to atmosphere. Works great the only issue is that, any vacuum I would be applying to my rings is negated by the open element breather. The best way to get around this is a check valve, which maybe someday I will get around to putting one on the atmosphere vent.

The evac system to your exhaust is a great setup but is only sufficient above about 3k and meant for drag motors. When added to an open vent works awesome. Simply speaking though it doesn't matter if it is venting to atmosphere or being pulled by vacuum from the intake system. Typically I disconnect the intake system, the only reason we do this today is emissions. The gasses coming out of the crank case are riddled with hydrocarbons. Although I will disagree on an engine producing more blow by than the PCV system can handle, all motors today under heavy loads see right around atmospheric and usually drop into a vacuum situation because the PCV is working well. PCV IS A MUST or else you will blow out seals, the only reason for the PCV is because you can significantly pressurize the crank case, i have seen one hit over 25 kpa and blow an oil pan gasket out. If its vented to atmosphere perfect, I hate putting it in my intake tract because the oil it will pull in wreaks havoc. You will get nasty intake valves, carbon and gunk build up in the runners and so on. If i run this to my exhaust who cares.
Click to expand...
well said A+
 
#25 ·
Ramrodd 69 said:
I was told this also from Patrick (Pro Systems). Told my builder this and
he disagrees. Said he never seen this happen and just had motor dyno'd
with 6 pulls (710hp, 685tq) and had no visable signs of this happening.
What is pan evac? Was told not to waste $ on vacuum pump for street
car (something to do with lack of oil maybe, do not remember). Other
option w/out PCV is 2 breathers and breather tank which should cut
down on oil mist in engine compartment. My concern with breather
way is been hearing without PCV on street car can due harm or some
kind of issues arise. Would like to go the 2 breather way myself and
use a breather tank to absorb some of oil mist which may come from
vc breathers which save me $. Once again, is there something that
could be harmful to my str driven car not using PCV. Also, if it may
matter, car is driven maybe 60 miles a week. Thanks! Bob
Click to expand...
Your 2 breather vented to a catch can will work fine for you.You wont harm anything without a pcv system and that setup.If you do want to go with a pump check out GZ motorsports their pumps are street friendly.Patrick from pro systems is familiar with large motors trust his advice.Pan evac is a breather system hooked to your header collectors to use exhaust velocity to create a vacuum in your crankcase.Again it is not as effective on large motors like yours,especially with mufflers, and basically ineffective at lower rpms.
 
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#27 ·
A pair of breathers won't cut it,..plus it's a bit Bubba-looking. A pair breathers simply allow the engine to belch and relieve pressure, but do little-to-nothing to remove harmful blowby vapors which includes water vapor. As a side note, it's very important your oil temp reach the boiling point of water (212 F) which vaporizes liquid water from the oil and crankcase. Then this water vapor and other harmful blowby gases are removed via a PCV system. It's why 160 degree thermostats are a bad idea.

Also, a PCV system reduces oil leaks and it's no secret that a bit of vacuum in the crankcase is good for HP.

I think a PCV system would be fine here, even though this is a fairly snotty BB.

The second best option would be an Evac system to the header collectors which pull fresh air through the crankcase from the air cleaner.

FWIW
 
#28 ·
When you drive the car on the street the stench from the crankcase vapors is overbearing.I run a vacum pump on my street/race car,and plan on putting a tube out of the catch can into my headers just to make the stench go into the exhaust and maybe even be burned off a bit.Right now I have a catch can with a breather right under the driver's side front hood seam and the vapor rising out makes the track officials point at my car trying to tell me that I am overheating.The engine is super tight with gapless rings and has been doing this since new so it isnt a worn out engine.A while back I was beating around in an 89 Mustang that I got from a friend who gave it to me so I could yank the hot rodded 302 and give it back to him.He had breathers on it and no PCV and driving the car stunk like a junkyard on a hot summer day.I put breathers with tubes into the base of the air cleaner and I could actually drive the car in traffic for a hour without the inside of the car looking a a cigar lounge from all the smoke.Again,it was a fresh motor,but without a way to vent the crank vapors out the car will always stink too much to be enjoyable to drive.I may be able to live with it and maybe some of my hot rod buddies,but do you really want to have 50 grand tied up in a car that a non car person will sit in and think is a cruddy old clunker because it stinks like gas and fumes?
 
#29 ·
I ran my previous setup 3500 miles on the street and race track(Road course,auto cross) and never got more than a few ounces of water in the catch can. I never noticed any overbearing crankcase oil vapor smell. I tore down the engine due to a distributor gear failure and the engine was spotless inside including the valve covers. I do run a 180 stat and the water vapor does get burned off and carried out the catch can breather.(You can see it as the car warms up. I keep an eye on the oil and changed it as needed. It really stayed looking good for quite some time.

My new setup will include two 12an hoses and Moroso catch cans. I'm also using a heat exchanger oil cooler in the radiator for two functions. To cool and heat the oil. I'll run a 180 t stat and that should make for quicker oil warm ups and oil temps over 200 normally. On the race track it will begin cooling the oil if it gets to hot. At least that's the plan!

I can see a PCV on a 90% street car or weekend drag racer. Road racing and autocross require much more time at high rpm and wide open throttle. Life's full of compromises. I'll plan for the torture instead of the putting around.
 
#30 ·
I say run the pcv system to start with,If it gives you trouble go to the 2 breather Bubba setup,if that gives you problems go vac pump.you wont know what will work in your situation till you try it.You can go by others experiences but each has different motors and usage and some just like to give opinions without any experience with your type of motor.Let us know what works for you so we can learn from it.
 
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#34 ·
Hey guys, this topic caught my eye when there was talk of routing pcv into the exhaust.Makes a lot of sense. I have an oxygen bung and could dump there . Question is what the pressure would be like in the collector area. If it were positive doesn't seem to be a place to "dump" engine gases . If negative would be great......so are you guys talking about a passive system here or only for positive pressure coming out of a vacuum pump?
 
#35 ·
My 422CI LSX had two valve cover breathers that would gather oil and run down the cover onto the headers, especially after a WOT pass at the track. I had planned on running a vacuum pump with a remote resivior but ended up selling the car before I had a chance.
 
#36 · (Edited)
Denvervet said:
Hey guys, this topic caught my eye when there was talk of routing pcv into the exhaust.Makes a lot of sense. I have an oxygen bung and could dump there . Question is what the pressure would be like in the collector area. If it were positive doesn't seem to be a place to "dump" engine gases . If negative would be great......so are you guys talking about a passive system here or only for positive pressure coming out of a vacuum pump?
Click to expand...
No it will be positive or atmospheric never vacuum in the collector. The evac systems take advantage of the exhaust flow, you flow high velocity gases across a tube that is suspended at an angle in the center of the collector. It creates a vacuum at the tube drawing out gases. This requires special pipes in the collector an O2 bung will not work.

I too have oil coming from my breathers down onto my headers but i just wipe it regularly before I have issues. Again I still doubt the vents to atmosphere couldn't handle a 502. You really are not having much more blow by because its all dependent on ring gapping. If it wasn't then your rings wouldn't be sealing and most likely fluttering resulting in scuffing your bore. Also take into account the turbo motors running around from the factory now, wouldn't you think the higher cylinder pressures and the potential for high pressure leakages from the turbo into the crank case higher than a 502 and yet these stock motors are running single PCV lines to the turbo inlet and fresh air line to the valve covers.

IMO, a vacuum pump is ugly and overkill. You can make mere horsepower for it and if you have good baffling you can stop oil loss through a breather, I am going to have some aluminum baffles welded in to my covers to cure this.
 
#37 ·
Its not only about ring seal and blow by when it comes to higher reving motors.You also have windage .On a 540 you have huge counter weights and 4.5" or larger pistons moving air and oil all over the place creating enough base pressure to actually cause resistance to the bottom of the pistons and the backside of the rings.this is why nhra prostock first found the vac pump freed up horsepower and the rest of the racing world was able to benifit from their find.Most turbo motors do now come with a vacuum motor to ventilate the crankcase and almost every race turbo motor has a vacuum pump.He's going to have to find out for himself what his situation is going to need.I only wanted to convey what i have experienced with a similar setup.My motor leaks down at only 2-3 percent so its not about ring seal.And i know a single pcv line doesnt work.
 
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#38 ·
If you are concerned about crankcase vapors leeching into the brake booster while running a single vacuum line for both PCV and booster, there is a very small canister filter that can be installed inline at the booster. It is in the Help! aisle at most auto parts stores and was used on C3 and C4 Corvettes. Part number is 80195 and I have one on my car. Also, the check valve on the booster should prevent most positive pressure from pushing anything into the booster.

I'll be the second one to say T'ing into the booster line is fine. What is the difference since they both are connected to manifold vacuum? They "T" inside the manifold anyway.

Image
 
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#39 ·
Radcannon said:
No it will be positive or atmospheric never vacuum in the collector. The evac systems take advantage of the exhaust flow, you flow high velocity gases across a tube that is suspended at an angle in the center of the collector. It creates a vacuum at the tube drawing out gases. This requires special pipes in the collector an O2 bung will not work.

I too have oil coming from my breathers down onto my headers but i just wipe it regularly before I have issues. Again I still doubt the vents to atmosphere couldn't handle a 502. You really are not having much more blow by because its all dependent on ring gapping. If it wasn't then your rings wouldn't be sealing and most likely fluttering resulting in scuffing your bore. Also take into account the turbo motors running around from the factory now, wouldn't you think the higher cylinder pressures and the potential for high pressure leakages from the turbo into the crank case higher than a 502 and yet these stock motors are running single PCV lines to the turbo inlet and fresh air line to the valve covers.

IMO, a vacuum pump is ugly and overkill. You can make mere horsepower for it and if you have good baffling you can stop oil loss through a breather, I am going to have some aluminum baffles welded in to my covers to cure this.
Click to expand...
Positive crank case pressure will also cause ring flutter.


Aluminum baffles welded into your covers will shield oil from splashing/slinging into the breathers but they do nothing to stop oil vapors.
 
#40 ·
The crank case has no ability to create pressure in the system unless there is a air leak to pressurize the case. The PCV system is more than adequate, no turbo motor in production today uses a vacuum motor for ventilation. Its all routed to the low pressure side of the compressor, the vacuum pumps are for wastegate control to keep the turbo out of boost for fuel economy. Vacuum pumps on drag motors help because of creating a vacuum in the case which creates less resistance for the moving parts and helps ring sealing.

You can vent your motor with baffles and be fine. Oil vapor will not create gunk in your engine compartment, only after time does it form carbon deposits in the intake tract. It takes a little while though. Just my two cents.

You are talking about a few horsepower here, and really it won't sacrifice durability. The only reason it could was if you were pulling a vacuum and had a breather because it would allow air with particles in the 15-40 micron range enter your oiling system and depending on filter performance can potentially knock a few ten's of thousands off your engine. Who here is expecting more than 60K though on a motor?
 
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