olescarb

I was told that the pcv system is something we learned from the Germans vehicles we captured during world war 2, thier convoys had very little smoke while our vehicles always had a blue haze from all the blow by. this story may not be true but...........

I would run a pcv system on any gasoline engine other than a supercharged or full race unit unless the engine has a dry sump oiling system. the suction side of a dry sump system will create a vacuum in the crankcase of the engine thus no need for a pcv valve.

The only time i see problems with pcv systems is when the engine does not have a baffle system between the pcv and the point where it goes into the valve cover. The pcv system should only pass crankcase vapors i have seen more than i car where the pcv valve had oil spray hitting the pcv valve thus passing oil into the intake system (not a good idea).

I hope this helps Henry @ olescarb

Ironcross

its gamesmanship...







thats a word, right? sounds good anyway...

Reggie Dunlop

I stand corrected on the early engines (409s, Hemis, 413s, 426s, 406s, 421s, etc). All the rest I listed did use it. PCV was really an emission requirement. And all those race motors stuffed in street cars had after 1967. Personally, I won't run it on a race car or a car with a gigantic cam and high compression. But for a street car, even a fairly hot number, there's no harm in using it. Dig the 'Cuda.

gkull

The output goes to canister with a breather vent and a bottom spicket to drain periodically

midyearvette

it was the first smog part..designed to let the engine eat the fumes and delete the road draft tube...

gkull

I said performance motors. Not some stock emission based factory motor. I've actually owned and driven some "stock" Muscle cars you listed when they were new. Very few muscle cars were much over a HP per CI. Go to any real performance aftermarket motor and you never see PVC


I was dynoing a V-12 tonight that i help rebuild and it did not have a PVC and it was factory race motor from the 60's. It actually had what every motor needs a dry sump

73, Dark Blue 454

The PCV system is absolutely needed on a street driven rig. All engines have some blowby. These gasses are toxic to an engine's life and need to be evacuated or your engine won't last as neary as long. Combustion is nasty business; hydrocarbons, acids, mositure, etc, all conspire to cause sludge, increased friction, and even rust inside the crankcase.

Breathers do nothing to evacuate the crankcase. They simply allow the engine to belch (and often make a mess of the engine bay).

The PCV system is beautifully engineered. The crankshaft, turning from 600 to 6000+ RPM, acts as a fan in the crankcase. Fresh air is drawn from the passenger's side valve cover and the harmful blowby gasses are pulled out of the driver's side back into the combustion chamber, which yes, helps performance.

Just as important to engine life and the PCV system, is operating temperature. Your oil needs to operate at 212 degrees or hotter to cook out the moisture in the oil (water boils at 212~). Once this moisture is turned to steam, then it can be evacuated through the PCV system. Otherwise you oil's ability to lubricate is reduced dramatically. That's why cars that always make short trips never have long lasting engines beacuse they never reach OT. Since water temp runs 15-30 degrees cooler than oil temp, I'm always amused by people who run 160* thermostats or none at all. Nonetheless, an oil temp gauge is worthwhile for this reason alone.

With the PCV system, the carbs were (are) simply metered and jetted accordingly. Non issue.

On a track car, who cares. You'll be tearing down the engine and rebuilding so often that PCV benefits (long engine life) don't come into play. Although most mills I've seen at the drags use something to evacuate the crankcase.

There are probably 100 supporting docs. Here's one (simply google "blowby PCV internal combustion engine" and you'd be hard pressed to find anything credible that says PCV is a bad thing):

http://www.yourautonetwork.com/pcv_valve.html

FWIW

71coupe

I would not just pull the PVC system & put a couple of breathers on the valve covers & call it a day. Do what chevy did on the L88's - road draft tubes...

baxsom

i have seen a lot of people put those oil/air separators like air compressors have inline on their pcv systems to keep oil out of the carb. do those work.

7T1vette

Why don't we just leave this thread as a "draw". There are those that swear the PCV system is unnecessary or useless...and we aren't going to change their minds. There are others...with documentation...who state that there is advantage to having the PCV system and that it does "no harm". Each group has had their say; let the OP decide what he/she wants to do. {No one is going to change anyone else's opinion on this one....}

63mako

Don't know but my 63 had a crude PCV. A fitting with a 1/8 hole in the base of the carb and a tube coming out of the oil fill tube in the manifold hooked together with a hose. Breather on the valve covers. I kept this functional when I went to a 3x2 setup to keep the oil mist off the engine.

Reggie Dunlop

Yeah, right. ;^~

2armor

May be a silly question but it doesn't matter what valve cover (left or right) the PCV is on does it? My PCV is on the driver side/breather on the pass side.

didn't know if the crank rotation has anything to do with this(?).

DRIVESHAFT

In theory there is a correct side, but even the OEMs have put them on different sides so I wouldnt worry about it.

2armor

I didn't think it would matter (much).

gkull

Not to pick on you. But just ask yourself the question: When does a motor have the most blow by? 2nd question: What amount of vacuum do you have at Wide Open throttle?

answer to 1. is: At a high VE point at or near max hp and TQ at higher rpms

#2: some motors can record less than 2 inches of vacuum and rising with rpm as the cfm limit of the throttle body is reached. Most engines never reach 1/2 of the max vacuum readings under no load light throttle

So when you need it most the PVC is not working at all. So the bigger the breather system the Better to vent off any crank case power robbing pressure.

Now cruising down the road at max vacuum the pvc is drawing crank case gasses, but i doubt that it draws enough to actually create any case vacuum that could be measured as a hp gain. Because it is also breather vented. I've ran numerous dry sump motors on the dyno. Dry sumps can create 20+ inches of vacuum in the case all the time. so they generally have an adjustable air bleed to limit vacuum. Because the max hp gain is up near 16-20 inches of vacuum.

73, Dark Blue 454

Somebody needs to study up. Here are a few starters.

http://www.valvoline.com/carcare/art...cid=2&scccid=3

http://books.google.com/books?id=U4T...esult&resnum=3

http://www.filtercouncil.org/techdata/tsbs/94-2R1.pdf

http://www.106rallye.co.uk/members/d...hersystems.pdf

http://www.absoluteastronomy.com/topics/PCV_valve

http://books.google.com/books?id=jco...um=9#PPA535,M1

http://www.underhoodservice.com/Arti...ts_breath.aspx

http://www.secondchancegarage.com/public/239.cfm

http://www.aa1car.com/library/pcv.htm

http://autonettv.com/category/auto-tips/pcv-valve

http://books.google.com/books?id=QLY...esult&resnum=6

I could google and add another 100 links but your turn. I'd like to see some credible sources that say the PCV system (or an alternate evacuation system) isn't necessary for a street driven engine and/or is a bad idea.

bashcraft

How much time does a street driven engine actually spend at WOT?

Mine, probably less than 5%. Much more than that and you probably won't have a drivers license for very long.

gkull

If you have PVC keep it and be happy. Keep your exhaust cross over heads and manifold. If you like those cast iron exhaust manifolds keep it. If you like your single exhaust system with Cat keep it! All that great stuff came on factory hot rods. OH, I forgot the EGR. That's great for your performance also.

If you are running tall valve covers with stud girdles or shaft rocker valve train. I would not go out of my way to drill a hole and mod them for a PVC line. If your have a modded engine where max power is you goal. Use at a minimum twin breathers or driven vac. pump.

When You spend $1000's to get the max CFM of air flow the last thing you want is oil mist carbon deposits baked on to those nice big intake valves

73, Dark Blue 454

Huh? Not sure what exhaust manifolds, cross-over heads, cats, and EGR have to do with this discussion but maybe you agree, that an engine, any interanl combustion engine, needs to be evacuated of it's cuastic gasses. The emissions benefit of a PCV system is simply an add on, or for me a "non-factor" (I'm not the first to hug a tree).

But don't take my word for it. Here are direct quotes from the links above: (BTW, I'm still waiting to see credible sources that say PCV, or an alternative evacuation menthod, is unnessecary. Or that two or three breathers is all that's recommended):

"If the crankcase is not adequately ventilated, the motor oil will quickly become contaminated and heavy sludge accumulations will begin to form. Internal parts, not protected by the motor oil, will begin to rust and/or corrode due to the water and acids that will become trapped within the crankcase."

"Blow-by is the gas that enters an engine’s crankcase during a normal combustion event or compression stroke. It is composed of unburnt fuel, air, and combustion by-products. Note that at this stage it does not contain any oil. Incidentally, the combustion by-products contained in blow-by gas are corrosive,.."

"A plugged or malfunctioning PCV system will eventually damage an engine"

"Why would I spend time with what should be “basic” information? Because it may actually be the single-most common factor contributing to issues of premature failure or customer dissatisfaction with a remanufactured engine. Do you recognize any of these symptoms of a potentially ineffective or inoperative PCV system: oil consumption (without smoking), fouled plugs, rough idle, plugged and sticking oil rings, rapid/premature engine wear, ruptured gaskets and seals, oil in the air cleaner, and potential detonation? Each can be explained, and none of them is a characteristic that any customer would consider acceptable for a freshly remanufactured engine."

"For example, at low or idle engine speeds manifold vacuum is high. This pulls the plunger (in the PCV valve) to the extreme forward position, or manifold end of the valve. Due to the shape of the plunger, vapor flow is reduced to a minimum. The low rate of the flow is adequate for ventilation purposes and will not upset the fuel/air mixture ratio."

"The flow of fresh air through the crankcase helped pull moisture out of the oil to extended oil life and reduce sludge" (Editor's note: see my post above regarding operating temperature and oil temp).

"...but some of the vapors from these explosions (combustion) escape into the lower part of the engine, called the crankcase. The crankcase is where your engine oil hangs out. These gases are about 70% unburned fuel. If the gases were allowed to stay in the crankcase, they would quickly contaminate the oil and turn it to sludge. Sludge is one of the biggest enemies of your engine, clogging it up, eventually leading to expensive failures. Also, the pressure build up would cause seals and gaskets to blow out. Therefore, these gases need to be vented out."

" It’s (PCV System) really a pretty simple system, but does an important job. The re-circulating air removes moisture and combustion waste from the crankcase, preventing sludge. This extends not only the life of your oil, but the engine as well. The PCV relieves pressure in the crankcase, preventing oil leaks."

"Blowby gasses enter past the piston rings into the crankcase during the compression and power strokes. These gasses will cause trouble. They form sludge and acids. The sludge can clog oil lines and spoil the lubricating system. This could damage the engine. Acids will corrode and this too can ruin the engine."

"As an engine runs, gases from the cylinders leak past the piston's sealing rings into the crankcase (containing the crankshaft and other parts). This leaked gas is sometimes referred to as "blow by" because the pressure within the cylinders "blows" them "by" the piston rings. These gases include compounds harmful to an engine, particularly hydrocarbons (unburned fuel), as well as carbon dioxide and water vapor. If allowed to remain in the crankcase, or become too concentrated, the harmful compounds will condense out of the air within the crankcase and form corrosive acids and sludge on the engine's interior surfaces. This can harm the engine as it tends to clog small inner passages, causing overheating, poor lubrication, and high emissions levels. To keep the crankcase air as clean as possible, some sort of ventilation system must be present."