Any harm not running a PVC valve?

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Any harm not running a PVC valve?

Post  69StangNate on March 31st 2015, 6:05 pm

New guy here who doesn't know much besides it is a lot of fun to smoke the tires all the way through first and second gear with my mild 466.  Anyway, after having a dead number 5 cylinder for some time that was hell to diagnose (it was due to both a bad plug wire and a bad pvc valve that was creating a basically a huge vacuum leak on that cylinder) I have just plugged the port for the pcv valve that taps into the #5 runner.  Should I hurry up and get a new pcv valve ordered and hooked up or does it not make any difference other than venting crankcase fumes out to the environment (OMG Twisted Evil) ?
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Re: Any harm not running a PVC valve?

Post  69StangNate on March 31st 2015, 6:07 pm

I meant PCV valve in the title obviously. Not poly vinyl chloride valve Ha Ha.
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Positive Crankcase Ventilation

Post  gcj on April 1st 2015, 5:30 pm

Since no one here with more knowledge has volunteered, here is a short tale of this system, as short as reading tolerance allows: Sleep

The total lack of crankcase evacuation leads to  severe buildup of water vapors and sludge inside your engine. Over time this may block various passages inside the engine and hinder the delivery of lubricants and it will destroy the lubricating qualities of even the best oils in relatively short time. You need some form of evacuation from inside the engine of gases, mixtures of gasoline, engine lubricant, vapor, soot, various solids from the combustion process etc, but most important of all - a control system for the enormous air pollution generated by unchecked processes like the ones described above, that take place inside any engine during the combustion cycle. Compression blow by.

High compression engines running on leaded or any form of high octane gasoline are the ..... worst ..... in the definitions fielded in the early 1960´s leading up to the first major Automobile Industry intervention by congress which lead to the enactment of the US NHTSA bill of 1966. The Clean Air Act of 1970 demanded further advances like unleaded gas and catalysts that became mandatory in 1975-76.

The first and by far the most effective piece of anti pollution legislation in the US was relevant paragraphs of this Act of 1966, where closed crankcase ventilation was mandated. Nothing that the legislative bodies did in those years did as much as this act to make the inner cities in the US livable again. People who remember strolling the sidewalks in most major US cities in those times will tell you that it was almost impossible to do during the summer months all the way from the mid 50´s up until around the late 70´s.

The integral part of the positive crankcase ventilation system is the P.C.V. - valve which is connected via a very rigid rubber hose directly to manifold vacuum, either at the base of the carburator base, the carb spacer or directly to a nipple on the intake manifold. The PCV valve is either mounted on the valve cover, engine block or in the intake manifold such as on some early FE motors, like the 406. The operation of the PCV valve is controlled by engine vacuum. If you have low vacuum at idle as most engines running cams with large overlaps do, then the vacuum signal at below 1500 rpm will be weak. In that case a vacuum pump may be the answer. Ford offered a vacuum pump like this in the Motorsport program for many years.

The end part of this system is the breather cap that on all OEM 429 Fords, serves the dual purpose of being the connector to the breather hose and oil filler cap. The hose connected to the oil filler cap / breather cap must be connected to a corresponding nipple on the air cleaner housing, inside the air filter area. This provides for clean air. This way the PCV valve sucks clean air through the engine that entered the engine through the air breather cap, AFTER it was filtered by the air cleaner. This last point, if observed, may increase the life span of piston rings, engine bearings, camshaft bearings, sleeves and motor oil many times over.

As far as the government was concerned in 1966 the name of the game was pollution. But, we as proponents of express transportation like our engines loud and powerful. High compression engines, governed with today´s  complex EMS devices do not like to have oil vapors, NOX, HC derivatives, water solids and second hand fuel mixture particles sucked back into our precious high horsepower machines. Adding those particles to the combustion mixture in a high compression engine causes all kinds of instability problems, like potential detonation and temperature issues as well as potential effects on flow characteristics in the exhaust side. Carbon buildup inside combustion chambers is also a product of excessive blow by and emissions particles being re-introduced into the process.

So, what to do?

As of today there are several solutions for the purists, one of which is a legit descendant of the Pro Stock wars of the 70´s. There you have valves in each valve cover connected to hoses running to modulators that plug into the header collectors. This type of crank case scavenging is effective on high RPM motors.

This presents a unique problem to street rodders and other high performance street going adventurers who like to obey the law and keep their motors clean.

The best answer to those people is locked in the engine building process. Example: If you are going to run 90% on the street and 10% on the track, then don´t build your engine with piston ring end gaps exceeding ,022 or whatever the specs may be. Stay within street high performance tolerances as specified by the piston and piston ring manufacturer. Do not use piston clearances intended for race engines on the street.

I have tried this last part on my big block Fox. It has loose race oriented tolerances for pistons and rings and it goes like this:

I stop at a red light and put the transmission in neutral to let the engine idle freely. After about 20 seconds my eyes begin to water. After about another 20 seconds at  the light people´s eyes in cars down to rows behind me begin to water. My clothes retain the stench for weeks on end .... a smell that is the mixture of aviation gasoline and lubricant.

.... Be safe ..

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Re: Any harm not running a PVC valve?

Post  TommyK on April 1st 2015, 6:16 pm

IMO a street car should have a working PCV system. PCV valve to carb manifold vacuum source, breather to air cleaner reduces the potential for oil leaks and keeps the engine bay clean.

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yup

Post  gcj on April 1st 2015, 6:26 pm

Agreed. Keep it clean and operations.

I think K&N offers some solutions. Others may do so as well.
G.

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Re: Any harm not running a PVC valve?

Post  Dave De on April 1st 2015, 6:33 pm

I have a car that gets about 60 runs per year at the track and 400 miles on the street. Itgoes 9.20s and has a pcv, 13,5 compression and e85. A working vacuum pump with sufficient air flow woild be better. I have no regrets with the pcv sytem. The best pcv line connection is at the plenum and the worst place is a runner for obvious reasons.
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Re: Any harm not running a PVC valve?

Post  69StangNate on April 1st 2015, 7:07 pm

Thanks for the wonderfully detailed explanation gcj. If I understand you correctly, the breather that hooks to the inside of the air cleaner actually draws air into the engine making for a complete loop of sorts and I was not aware of that at all. Based on this info I will look into getting a new one purchased and will hook it up at the base of the carb instead of the #5 runner like it was previously. I have Ford Motorsport chrome valve covers where the pcv comes out of the side of one of the oil fill caps horizontal instead of the normal vertical orientation so I don't think I can get a replacement from the parts store.

Thanks,
Nate
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Well, I .....

Post  gcj on April 2nd 2015, 5:28 am

.... should have enumerated exactly how the system works and where the need for it begins:

1. As you crank your engine and it fires up, the gases and various pollutant chemicals and compounds turn loose inside the engine cavity/crank case as a result of compression blow by. Mostly. (others chime in here at will, add or subtract)

2. The issue at the onset was: How do we get rid of this stuff at the lowest cost to the atmosphere? The best answer: Burn it as much as possible. But how? You can not just stick a hose into one valve cover and hook it directly to manifold vacuum. Enter the next invention: The PCV (Positive Crank case Ventilation)

3. The PCV valve has a steel ball inside which, if operating properly will sit in its place sucked up to the upper sealing surface of the internal chamber. Pulses generated by each compression stroke will cause a momentary lapse in vacuum, sending a signal to the valve to open up and let the mess back into the induction system where it originated. Manifold vacuum has a very large part in the proper operation of the valve. Engines with large overlaps on the camshafts generate less vacuum at idle and low RPM as you may have felt when you needed the assistance of your power brakes and found the booster empty. Therefore you need to shop around for a valve that matches the vacuum signal of your engine. For stock engines, make SURE you have the correct caliber valve. Otherwise you will have poor idle characteristics, unexplained running problems at various engine speed plus the inevitable mess that will generate inside your HP motor, with no explanations available and all kinds of theories as to what the problem may be. People have torn down blueprinted engines because of this and unexperienced mechanics overlook this 10 dollar question. So, if you have unexplainable problems in the running of anotherwise great engine, take a hard look at this part.

4. To generate a closed system, which let only clean air into the crankcase we needed some kind of device that would guarantee dust free air to be let in at the other end of this cleaning system. That is why, after 1966, we have oil filler caps with a 5/8" nipple on the side or the top where we have a rubber hose that connects to an area INSIDE the air cleaner, where it gets FILTERED air to let into the crankcase.

5. If you look at these oil filler caps as applied during these performance years, you will notice that the cap is open underneath, but partially blocked by a wire mesh filter or in some cases with other materials like sponge or the like. This system is thus still open to the atmosphere. This is a safety device set up so you don´t blow out valve cover and intake manifold gaskets or even timing cover and oil pan gaskets during unusual events like a  500 horsepower motor going through the motions at 7.500 rpms.

The next step in this cleanup was the fuel vapor system mandated in 1971. If you have a 1971 car you will see a 2 quart black canister on the RH. side of the engine bay, usually mounted on the inner fender or torque box. It is connected to the air cleaner base with two paper or aluminum hoses. When you turn off the engine, the intake will emit unburned fuel and air back up through the carburetor. This gas mixture is siphoned into the canister where it gets captured by a very fine mesh filter consisting of pure carbon in semi solid form.

When you crank the engine, it sucks this mixture of gasoline and air back in and burns it.  

Then we had EGR systems, Thermactors and catalysts, but our high handed engines lost out to all that stuff ....




Happy Easter all ..

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Re: Any harm not running a PVC valve?

Post  69StangNate on April 3rd 2015, 8:34 pm

Thanks again gcj for the detailed information.  With respect to the proper PCV valve for an engine like mine with a large cam and low vacuum at idle (about 6.5" at idle in gear), can anyone on here recommend what to get?  I was thinking that if I asked the parts store for one for a 429 SCJ engine, that might get me close, but not sure.  Also, as mentioned previously the pcv valve installs horizontally in the side of one of the oil fill caps.  From what I have seen on the web, most people say they should work fine on there side instead of vertical, but I am skeptical to be honest.  Does anyone on here run one that is horizontal with no problems? Thanks in advance.
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