When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
2005 LQ9 that had 170k on it. Completely stripped down and rebuilt with:
Enginetech p50418 Hypereutectic pistons STD Bore
Engine Tech rings, file fitted
LS3 Head Gasket
LS3 Heads (Gone through and redone)
Texas Speed LS3 Stage 2 cam
It currently has around 300 miles on it. I did the first 100 or so miles with Lucas break in additive and synthetic (yea I know its not recommended) mobil 1... I since changed it with regular Castrol 10w-30 and a full bottle of lucas break in additive. The car runs great and has plenty of power, I just noticed the smoke from the breather vents on the valve covers. It currently has 0 PCV system. Its just blowing to atmosphere from uncovered factory valve cover ports. See the attached video.
Looks like steam to me. It happens. Mine does it from my vented catch can. I’ve researched it extensively and it boils down to the ethanol in the fuel creating moisture that gets pushed out of the breather, without a pvc setup. Lots of guys experiencing this same issue.
No, not too much imo. Set the cap on so it’s loose and not threaded, rev the motor up to 3500-4K, if the cap jumps up or off where it’s sitting, you have too much crankcase pressure.
You need a pcv system. If you care about the engine and controlling the oil flow (keeping it inside the engine)
The PCV has nothing to do with keeping oil in the engine as long as it vented.
The PCV system is part of the emissions system to burn crankcase vapors rather than release them to the atmosphere. The PCV system actually contaminates the combustion process and that's the main reason people run a catch can on a high performance application, A catch can will remove some of the contaminants before they reach the intake.
Running a PVC system is still a good idea because it removes contaminants from the crankcase under vacuum and that helps keep your engine cleaner and your oil will last longer.
If you choose not to run a PCV It's still a good idea to run at least a catch can so you're not spewing the vapor all over your engine compartment.
Has anyone actually sent in the same identical type of used oils in for analysis? One being an engine that vents to atmosphere after 2500 miles and the other via PCV after 2500 miles. I'm willing to bet there won't be much of a difference if the oils had equal levels of abuse. Most of what you see coming from a breather can or valve cover breather is moisture and I've yet to open the valve and see oil spewing out of my breather can.
Has anyone actually sent in the same identical type of used oils in for analysis? One being an engine that vents to atmosphere after 2500 miles and the other via PCV after 2500 miles. I'm willing to bet there won't be much of a difference if the oils had equal levels of abuse. Most of what you see coming from a breather can or valve cover breather is moisture and I've yet to open the valve and see oil spewing out of my breather can.
I haven't myself but I used to work in mass transit about 30yrs ago, They sent samples in for every vehicle every 5th oil change. The report would detail what was found and possible causes. On gasoline engines the PCV system was a frequent repair so they must have seen something.
I do know from experience that that pre-pcv engines were nasty after 60-70 thousand miles and not nearly as bad when cars were outfitted with PCV valves. Gasoline and the oil itself has improved over the years so I'm sure that also helps. When I pull apart an engine with 150,000 miles it looks great compared to an old engine with 50,000.
Another thing to keep in mind is how the engine will be used, If it's a lot of short trips with very little time for the engine oil to come up to temperature I would change oil more often. If it's a serious street strip engine then I wouldn't bother with a PCV because the engine life is likely to be shortened anyway. On a race engine I would run a vacuum pump or at minimum a vented catch can(s) and change oil often.
sorry wrong. What good is a dry sump if it doesn't keep oil inside the engine? What good is a vacuum pump if it doesn't keep oil inside the engine?
What do you think the purpose is of the WOT fresh air pcv tube and restrictive paper air filter element from the factory?
PCV of all kinds is an integral absolutely critical component for high-mileage daily drivers which assists in oil quality and oil containment.
Here we go again, He has a mild rebuilt LQ4 not a race engine.
Venting to the atmosphere is not going to cause any oiling issues that wouldn't already be present with a PCV system. It will not use less oil with or without a PCV system but can actually lead to higher oil consumption.
You must not understand how a PCV system works in the performance world because it really does very little if anything under WOT. The manifold vacuum is at it lowest and the crankcase pressure is at it's highest and in many cases the vapors are forced out of the fresh air inlet of a stock type PCV system.
They work great when at idle and part throttle (Intake manifold is pulling a vacuum) On a performance engine pulling in those very same vapors can lead to detonation because of the lower octane caused by oil and combustion contamination.
And since you brought it up the reason a dry sump is preferred on a performance engine has little to do with crankcase ventilation but everything to do with oil control/windage/aeration and ring seal, Keeping the seals in the engine is an added benefit of running that setup.
A vacuum pump helps ring seal and keeps the seals in an engine but is severe overkill on a mild build that isn't seeing high boost and are also vented to the atmosphere.
On a mild performance build like the OP has there are pro and cons to running a PCV system and the same can be said about running a vented catch can. Keeping the oil in the engine is not even an issue either way.
How would venting to the atmosphere cause the engine problems as you stated and exactly how does the PCV control oil and keep it in the engine as you stated here?...>" You need a pcv system. If you care about the engine and controlling the oil flow (keeping it inside the engine) Basically what you are saying is an oil catch can doesn't catch oil/vapors or that you like burning oil and combustion vapors in your engine because it's better for it?
By the way, Changing oil more often fixes any issues related to oil contamination due to lack of PCV.
Last edited by LLLosingit; 09-07-2019 at 01:06 AM.
no matter what you type, there will always be a difference between 14.5psi of atmospheric pressure, and the pressure in a crank case of any running engine
pressure goes above atmospheric = helps oil escape
doesn't matter how big the vent is or what engine manufacturer. Pressure on the gauge is everywhere, every surface inside,the piston seals literally point into the pan. I don't even want the original14.5psi in there if I can help it. Let alone any additional from piston seals. Pressure is collisions of air molecules with the inside surfaces of every oil seal. The more of that, the faster the leak, the more they leak. Break a piston seal and see how much oil sprays out due to pressure on any setup. They will all leak eventually but how quickly until it starts? We are considering a rate equation, where the rate of oil consumption/leaking is related to the pressure in the crankcase over some time interval.
no matter what you type, there will always be a difference between 14.5psi of atmospheric pressure, and the pressure in a crank case of any running engine
Well that pretty much sums up the reason for the OP post Mr Obvious, And a PCV does little to alleviate the problem under WOT conditions.
If you have so much blow by in a mild performance build that you're blowing oil past the seals a PCV system isn't going to fix the problem that is causing the issue, All it's going to do is suck all the blowby into your combustion chamber.
If it's properly vented it won't build enough pressure to be a problem, In most cases something as small as a pair of -6 lines is enough from the factory valve covers.
On my roots blown 408 I run 2x -12 lines from the valve covers to a large catch, Anything short of rod ventilating the oil pan for me it should be enough catch all the oil even if I burn a piston.
I run a Mighty Mouse vented catch can on my high compression 441 on E85 and my vent at the top shows the exact same thing, Steam condensation from the ethanol....
a PCV does little to alleviate the problem under WOT conditions.
Strongly disagree. PCV is absolutely critical component of wide open throttle for non-race engines, regardless of whether the engine have vacuum pump or natural aspiration, additional vacuum in the crankcase is an oil control strategy to slow the rate of oil leakage over time (thus the original post #1 comment about needing PCV) and it improves piston ring seal character. The rate at which oil moves through engine seals in general is directly related to crankcase pressure over time.
You are suggesting to simply vent the crankcase which does not provide any 'positive' ventilation. The piston seals point directly into the oil pan. Each cylinder fires and provides a pressure spike from those piston seals into the oil pan which is a hot burst of pressure that will attack every surface equally including front and rear main seals, valve cover gaskets, front and rear covers, the whole crankcase takes a hit that it didn't deserve.
There needs to be a low pressure so when the piston seal fires its hot burst of pressure into the oil pan area, the low pressure pulls that wave away before it can harm the oil seals or interact with engine oil. Thus is the principle of vacuum pump strategy oil containment while using low tension piston oil seals.
Vacuum pump level of pressure is not recommended for wet sump application. However the crankcase can be programmed to almost any pressure by adjusting fresh air restrictor, which is present on most engines from the factory.
For example here is the factory LS route. Check valve in this case is typical pcv valve which sets the orifice from the factory.
The vent is 3/8" or maybe ~10mm or so, also set by the factory (In the valve cover). The tube is the orifice diameter in this case, however in many factory engines there is a physical restrictor in place in addition to a larger tube presumably the additional volume is for less possibility of becoming clogged.
If it's properly vented it won't build enough pressure to be a problem, In most cases something as small as a pair of -6 lines is enough from the factory valve covers.
On my roots blown 408 I run 2x -12 lines from the valve covers to a large catch, Anything short of rod ventilating the oil pan for me it should be enough catch all the oil even if I burn a piston.
I'll repeat another way so you can understand better.
If I go to build an engine for a street car. I use the tightest oil seals possible to make oil control a breeze. So of course it would be fine with just a can. LOL
Obviously any engine we use SHOULD be fine with just a can. If the engine is healthy then it should not even need the can in the first place or any pcv to stay clean.
So the caveat
I spent years volunteering in a variety engine import shop and on average saw one container of 55x engines of various manufacture come in high cube twice per month sometimes.
One of things I helped with wash the engines and dismantle/reuse broken parts or engines, put together complete swaps from misc. parts.
As You might imagine that most of these engines were performance oriented and turbocharged, and many were highly modified with the sickest parts I've never seen here in America on a muscle car. You guys can't even get Volks. Anyways, alot of 'noobs' would remove the pcv from engines just like you are suggesting to do and then drive them 40-50k miles or so. Almost every single OEM pcv engine that came through was gorgeous under the valve cover and leak free for years to come. And almost all of the engine where somebody had mangled or dismantled the pcv system were rough looking, sludgy, they looked mal-maintained. My sample size is near one thousand. One thousand engines I estimate to have come through and I looked, washed, determined, pulled many of them apart (around 5 to 7% of them) and made complete swaps, helped install into cars, fabricated, wiring, welding, tuning, etc... I learned anything I could given the free opportunity.
My experience led me to try and understand why the engines without pcv looked so terrible.
I wrote about it above you already know, hot pressure spikes in the pan, need somewhere to go Our perfectly leak free engine with the vented atmosphere can is going to be leaking from every oil seal and the engine oil will have a permanent, discoloroued brownish hue by the time it reaches 50-60k miles, even if we use total seal rings and 5% leakdown. If it makes any real power, some percentage of that pressure winds up in the oil pan, if it is allowed to mingle with the engine oil the hot reactive conditions are favorable for reactions to proceed (hotter = easier to react in chemistry) and the very hot gas state molecules squeezing around piston oil seals are headed directly for the blood of the engine (oil) and other such escapies, where they can react and form any number of unexpected molecular conformations.
So was the caveat obvious? Yes you can run without the pcv and just use a vent. But you have created a 50k miles max motor before it looks like a leaking pile of poo
Whereas if you keep the pcv and shoot for proper 2-4" Hg pressure drop at WOT, oil stays in the engine as it approaching 50k and will go even 150-250k without much oil appearing around the seals, oil stays cleaner overall color remains intact (nice and syrup and smells good), piston seal performance is improved, engine remains healthier overall. So of course I build it super tight, but then I also go the extra step, in the nature of highest performance (tech superior and automotive skills only approve) and keep the pressure down in the crankcase at WOT to preserve the oil seals and improve the piston-ring seal in effort to keep the engine healthy long term.
Its sort of like smoking. You can start and it will have no apparent effect. keep smoking though... look what eventually happens
The part you seem to be overlooking is that performance builds often exceed the capability of the stock PCV system and forces vapor/oil out of the fresh air side of the system and this has been well documented on LS based engines. It happens quite often on completely stock engine once they have started to wear considerably. I've seen it happen to low mileage stock engines that have seen sustained high rpm usage (highway pulls). These engines are also sensitive to the type of oil being used to the point that engines might use 2-3 quarts between oil changes suddenly only using a qt because of a brand change.
A stock type PCV system does nothing for ring seal...not even a little because it's not a closed system, all it does is pull air from the intake side of the system to the manifold, It does not create a vacuum in the oil pan so it does not help ring seal. Think about what you're implying for a second, You're basically saying that under wide open throttle your manifold has enough vacuum to pull on the oil pan so hard through a small hose that it overcomes the fresh air inlet and the blow by the engine produces to the point that you would have a measurable negative reading at the pan... I'll guarantee you that's not happening.
Hook up a gauge on your oil pan and show me how much vacuum it reads..... If it has reading at all it will be a positive reading because you done blew your **** up lol
A PCV system is not vital for performance as it actually hurts instead of helping. Like I've said many times already, You're sucking oil/combustion vapors into the combustion chamber, That brings down the octane rating and can lead to knock....What does the computer do when it see's knock? It pulls timing. Pulling timing does not help performance. The fact is a PCV system is an emission component not a performance component. On a stock engine I leave it fully functional because it does serve a purpose, On a performance engine where I want to make as much power as the combination is capable of then I don't run them, I run a catch can.
You want the best of both worlds you run a vacuum pump where you actually do help ring seal and you can actually pull the vapors from the engine....Yes you can run a vacuum pump on a wet sump system...it's done all the time and you would know this if you had any practical real world experience with high performance engines.
EDIT: Why can't you just admit when you really don't know what you are talking about? You seem semi intelligent but lack common sense, I know you have very little experience with V8 engines and even less when it comes to the LS variety. Sometimes you should learn from people who have first hand experience and quit relying your book smarts because that usually makes you look foolish. I'm not right all the time and will admit when I'm wrong and still learn something every day.
Last edited by LLLosingit; 09-09-2019 at 04:15 PM.
Your quote Kingtalon...”If the engine is healthy then it should not even need the can in the first place or any pcv to stay clean.”
Yet you state that you’ve torn down all of these import engines, and they were filthy BECAUSE they had no PVC? Your talking out of both sides of your mouth. Please make sure you have some knowledge about what your saying before you post.
08-29-2019, 07:27 PM
Is this too much blow by? 
