PCV valve,can I remove?
Burning Brakes
Joined: Dec 2007
Posts: 952
Likes: 0
Let me say this one more time (I think the 3rd time) in the vain hope you actually read it.
PCV was developed in the mid 60's to reduce smog.
Irrelevant to the arguement that they are detrimental or not.
The arguments that blow-by hurts the internals of the engine were based on that point in time.
Relevent. We are still talking about the same design
Let me try and catch you dinosaurs up on 40 years of engineering.
Oil - In the 1960's we were using very basic mineral oil, it had no detergent additive and was a single weight. It was so poor many vehicles required oil changes every 1000-3000 miles.
Fuelling - In the 1960's a gallon of gas cost 30¢, people didn't know or care what MPG was, if the car was off tune and dumping 3x the needed fuel into the engine no one cared. Likewise they didn't know or care about the black stuff coming out of the exhaust.
Tuning - In the 1960's cars were tuned by ear. If you were a real specialist you might use a vacuum gauge but that was it. Cars often ran excessively rich AF ratios, the driver didn't care as long as the car lit the rear tyres.
Development - As oils, fuelling and tuning improved many manufacturers disliked the idea that having spent millions on engine development they would leave the engine tune to 50¢ air leak. Unfortunately politicians still thought cars were the devils work so they compromised and used a non-positive closed system. This routed crankcase fumes to the air filter housing/box but allowed them to vent out themselves rather than using manifold vacuum to suck them out.
Whetrher above or below the manifold is irrelivant. It's still a low pressure area.
The Modern Day.
Oil - Now it's capable of going 10-15-20K before changing, it can do this because of the refining process, it's multi-weight, has longer polymer strands, plus the addition of stabilizing and detergent additives. The hydrocarbons they may have damaged 1960's oil now barely touch modern oil.
Fuelling - Look at peoples awareness of MPG, even you guys who often only use your cars on sunny Sunday still worry about MPG. This awareness makes you constantly concerned about how much fuel you're dumping into your engine.
Tuning - Today's carburettors are built mainly to run on the weak side of AF ratios, they are easier to tune and even if you take your orginial carb equiped car to the shop the tech uses a computerised engine analyser or maybe a chassis dyno, not his ear and guess work.
Development - Many engines designed after the 1960's don't use PCV, if the system is so essential why was this? It was because it was out dated, antiquated system that was no longer necessary. Today it is only fitted to cars sold in areas with the strictest emission laws and is often computer controlled.
Irrelivant. Modern cars are also fuel injected, which also reduces raw fuel in the crankcase.
So let me sum up.
Will an open system blow gaskets - noCorrect, and irrelivant
Will an open system cause sludge - noIrrelivant
Will an open system cause internal corrosion - noProve that one
I can tell you all these are true because cars that only have a non-positive closed system will regularly do 250-500k with no engine overhauls.Also irrelivant
Does PCV hurt performance - yesShow me the data.
Can an open system be clean - yesIrelivant
PCV belongs with stuff like cross-ply tyres and copper ignition wires, if you want to keep the car original then go with it. If you want performance throw it in the trash and forget about it.
You keep comparing modern tech with old. This engine was designed in 1955 or so. Most people retain carburetors that also wash the cylinder walls with more raw fuel than modern engines, which ends up as volatiles in the oil.
Show me some hard data that PCV on an old engine with modern oils is detrimental. Data, and less conjecture.
Burning Brakes
Joined: Dec 2007
Posts: 952
Likes: 0
Speaking of that, I have a new hero in life- Lord Monckton. Please watch:
http://www.youtube.com/watch?v=OzkB5DuveDE
Pro
Joined: May 2003
Posts: 593
Likes: 0
From: London England
OK, I'm finally going to admit defeat in this thread.
I'm quite a tenacious person but even I have my limit, there are only so many times I can type the same cold, hard facts and try to reply to an argument of "you're wrong, and if you want me to prove it I'll just type it louder".
I'm fed up with trying to explain engineering fact to people who either skim read what I've posted or lack the fundamental background knowledge of the operation of the internal combustion engine to make an educated argument.
I cannot believe how backward thinking a few of the forum members are. How many people have to tell you the same thing before you'll believe it?
I only need to look through this forum to see technological ignorance reach a new level.
Carbs can out perform EFI, rubber bushes are better than Poly, points are better than electronic, drilled discs are a myth, I'm surprised you don't think your cars run on steam and witchcraft.
You're such sheep, the EFI situation is a good example, people dismiss it until a few key old fashioned players suddenly say it's 'ok', then on mass the rest of the pitch fork mob accepts it.
You thoroughly embarrass the rest the of the Vette community not living in the 1960's.
I'm quite a tenacious person but even I have my limit, there are only so many times I can type the same cold, hard facts and try to reply to an argument of "you're wrong, and if you want me to prove it I'll just type it louder".
I'm fed up with trying to explain engineering fact to people who either skim read what I've posted or lack the fundamental background knowledge of the operation of the internal combustion engine to make an educated argument.
I cannot believe how backward thinking a few of the forum members are. How many people have to tell you the same thing before you'll believe it?
I only need to look through this forum to see technological ignorance reach a new level.
Carbs can out perform EFI, rubber bushes are better than Poly, points are better than electronic, drilled discs are a myth, I'm surprised you don't think your cars run on steam and witchcraft.
You're such sheep, the EFI situation is a good example, people dismiss it until a few key old fashioned players suddenly say it's 'ok', then on mass the rest of the pitch fork mob accepts it.
You thoroughly embarrass the rest the of the Vette community not living in the 1960's.
Last edited by Golden; Dec 19, 2009 at 09:56 AM. Reason: spellink
Race Director
Joined: Jul 2001
Posts: 15,892
Likes: 42
Not unarmed, uninformed or better yet- misinformed. Big difference. If you're going to stand up in public and shout that 'the sky is falling', best be prepared for those that will challenge that position. The greenpeacer in the video got what she deserved, as did the group he labelled as the '**** youth' who disrupted the proceedings.
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
Golden
There was another very long thread about this a while ago and I used a gauge to measure various conditions.
One result I didn't make too clear:
With the pcv valve disconnected and the guage hooked to the dipstick tube there was pressure recorded AND the lower seals both front and back started leaking. They did not leak before.
You should be able to find the complete thread from this too, with pics showing a slight vacuum under normal conditions with the pcv connected.
You can draw your own conclusions from some real data.
There was another very long thread about this a while ago and I used a gauge to measure various conditions.
One result I didn't make too clear:
With the pcv valve disconnected and the guage hooked to the dipstick tube there was pressure recorded AND the lower seals both front and back started leaking. They did not leak before.
You should be able to find the complete thread from this too, with pics showing a slight vacuum under normal conditions with the pcv connected.
You can draw your own conclusions from some real data.
Here’s some more info to mull over.
Had a little time to get some reading on the road today. Traffic was pretty heavy, so I didn’t get a lot.
I connected my “lower than atmospheric pressure gauge” (because Z-man and FB007 contend vacuum does not exist) the same as before, to the oem passenger valve cover breather tube.
I taped the gauge over the shadowband, so it’s not as clear as should be with the bright Florida sun behind it.
At startup and idle I got the same reading of 6”
After the engine got to full temp (180°) it went up to 7”
At 2000 rpm steady cruise it went back to 5”
At 2500 rpm steady cruise it stayed at 5”
At 3000 rpm steady cruise it stayed at 5”
At 3500 rpm steady cruise it dropped to 4.5”
At 4000 rpm steady cruise it stayed at 4”
Traffic wouldn’t let me cruise at any higher rpm
Half throttle acceleration thru 1st, 2nd and into 3rd stayed at 4”
Full throttle acceleration brought it to .5# pressure.
Thru all of the cruising rpm’s the needle stayed pretty steady.
At WOT acceleration, thru the gears, there was a lag of 3 or 4 seconds to reach pressure.
Had a little time to get some reading on the road today. Traffic was pretty heavy, so I didn’t get a lot.
I connected my “lower than atmospheric pressure gauge” (because Z-man and FB007 contend vacuum does not exist) the same as before, to the oem passenger valve cover breather tube.
I taped the gauge over the shadowband, so it’s not as clear as should be with the bright Florida sun behind it.
At startup and idle I got the same reading of 6”
After the engine got to full temp (180°) it went up to 7”
At 2000 rpm steady cruise it went back to 5”
At 2500 rpm steady cruise it stayed at 5”
At 3000 rpm steady cruise it stayed at 5”
At 3500 rpm steady cruise it dropped to 4.5”
At 4000 rpm steady cruise it stayed at 4”
Traffic wouldn’t let me cruise at any higher rpm
Half throttle acceleration thru 1st, 2nd and into 3rd stayed at 4”
Full throttle acceleration brought it to .5# pressure.
Thru all of the cruising rpm’s the needle stayed pretty steady.
At WOT acceleration, thru the gears, there was a lag of 3 or 4 seconds to reach pressure.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
If you say the PCV is costing me 50 HP then I'm tossing the damn thing and not worrying about the contaminants.
If you say its a couple HP then I think the trade off is worth it and I'll keep it.
Burning Brakes
Joined: Aug 2005
Posts: 1,164
Likes: 1
From: Europe, France
I removed the PCV valve one year ago, mainly because the engine was idling better without it and the spark plugs were cleaner.
But I didn't notice ANY difference in power. I don't say there is no difference, but in my case it was not significant.
But I didn't notice ANY difference in power. I don't say there is no difference, but in my case it was not significant.
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Race Director
Joined: Oct 2000
Posts: 15,013
Likes: 79
From: central FL, near the beach.
Golden
There was another very long thread about this a while ago and I used a gauge to measure various conditions.
One result I didn't make too clear:
With the pcv valve disconnected and the guage hooked to the dipstick tube there was pressure recorded AND the lower seals both front and back started leaking. They did not leak before.
You should be able to find the complete thread from this too, with pics showing a slight vacuum under normal conditions with the pcv connected.
You can draw your own conclusions from some real data.
There was another very long thread about this a while ago and I used a gauge to measure various conditions.
One result I didn't make too clear:
With the pcv valve disconnected and the guage hooked to the dipstick tube there was pressure recorded AND the lower seals both front and back started leaking. They did not leak before.
You should be able to find the complete thread from this too, with pics showing a slight vacuum under normal conditions with the pcv connected.
You can draw your own conclusions from some real data.
and a high power or worn engine overwhelms the valve, like on my 67 289. Connecting to the air cleaner base does vacuum the gases out of the crankcase, but in a higher volume than the pcv valve.
i actually learned something 
Last edited by Matt Gruber; Dec 19, 2009 at 12:17 PM.
Burning Brakes
Joined: Dec 2007
Posts: 952
Likes: 0
Dang you don't have to get so mad , I know I'm not the sharpest tool in the shed but I just ask a couple questions so I can make a decision on what I feel is best for me.
If you say the PCV is costing me 50 HP then I'm tossing the damn thing and not worrying about the contaminants.
If you say its a couple HP then I think the trade off is worth it and I'll keep it.
If you say the PCV is costing me 50 HP then I'm tossing the damn thing and not worrying about the contaminants.
If you say its a couple HP then I think the trade off is worth it and I'll keep it.
2)At cruise, a PCV is also at peak level. How much HP is required for cruise? 35-45HP?
3)At WOT, a pcv does zero. Thusly, at WOT, a pcv has no impact.
4)Even race cars use vauum pumps/dry sump set ups due to negative pressure adding performance. What draws less HP? A mechanical pump or a stupid metering valve?
5) Blowby is unburned gasses. Reintroducing them to the intake side can do little harm. It originated there in the first place.
6) Every English car manufacturer goes bankrupt.
Le Mans Master
Joined: Jan 2003
Posts: 6,575
Likes: 1
From: Tuttle OK
Cruise-In VIII Veteran
OK, I'm finally going to admit defeat in this thread.
I'm fed up with trying to explain engineering fact to people who either skim read what I've posted or lack the fundamental background knowledge of the operation of the internal combustion engine to make an educated argument.
I cannot believe how backward thinking a few of the forum members are. How many people have to tell you the same thing before you'll believe it?
I only need to look through this forum to see technological ignorance reach a new level.
Carbs can out perform EFI, rubber bushes are better than Poly, points are better than electronic, drilled discs are a myth, I'm surprised you don't think your cars run on steam and witchcraft.
You're such sheep, the EFI situation is a good example, people dismiss it until a few key old fashioned players suddenly say it's 'ok', then on mass the rest of the pitch fork mob accepts it.
You thoroughly embarrass the rest the of the Vette community not living in the 1960's.
I'm fed up with trying to explain engineering fact to people who either skim read what I've posted or lack the fundamental background knowledge of the operation of the internal combustion engine to make an educated argument.
I cannot believe how backward thinking a few of the forum members are. How many people have to tell you the same thing before you'll believe it?
I only need to look through this forum to see technological ignorance reach a new level.
Carbs can out perform EFI, rubber bushes are better than Poly, points are better than electronic, drilled discs are a myth, I'm surprised you don't think your cars run on steam and witchcraft.
You're such sheep, the EFI situation is a good example, people dismiss it until a few key old fashioned players suddenly say it's 'ok', then on mass the rest of the pitch fork mob accepts it.
You thoroughly embarrass the rest the of the Vette community not living in the 1960's.
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
Race Director
Joined: May 2005
Posts: 10,674
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From: Millington Illinois
St. Jude Donor '08-'09
Le Mans Master
Joined: Nov 2008
Posts: 5,691
Likes: 12
From: columbus oh
Dang you don't have to get so mad , I know I'm not the sharpest tool in the shed but I just ask a couple questions so I can make a decision on what I feel is best for me.
If you say the PCV is costing me 50 HP then I'm tossing the damn thing and not worrying about the contaminants.
If you say its a couple HP then I think the trade off is worth it and I'll keep it.
If you say the PCV is costing me 50 HP then I'm tossing the damn thing and not worrying about the contaminants.
If you say its a couple HP then I think the trade off is worth it and I'll keep it.
p.s.....to equate a mechanical vacuum crankcase pump to a pcv valve is ludicrous.....you are comparing an outside vacuum source that evacuates blowby to one that is made by the mill and plumbed to the plenum....
Last edited by midyearvette; Dec 19, 2009 at 04:28 PM.
Burning Brakes
Joined: Dec 2007
Posts: 952
Likes: 0
2) A PCV lowers the crankcase pressure.
3) A road draft tube, under high speed, moderately lowers the crankcase pressure due to the venturi effect.
4) A header venturi system lowers the crankcase pressure.
Last edited by FB007; Dec 19, 2009 at 04:44 PM.