Looking more, the inlet tube from air cleaner actually becomes the exit tube at high speeds and high loads when the vacuum is near zero (no PCV flow, or action then ) but engine generates a lot of blowby…the most in fact. In that case it (by design) it is intended to flow backwards up the air intake to the air cleaner where it is sucked in due to high air flow there under those heavy loads and burned. So another aspect to it. That is why oil is often at end of it in air cleaner!
At idle and high vacuum it is almost plugged by a proportional to vacuum check , (orifice type action)—but at medium vacuum it allows high flows to purge engine , which has little impact compared to disturbing idle air. If blow by exceeds PCV flow it backs up into the air cleaner by design.
I think some mopars have the PCV inlet hose on the downside (clean side) of air filter..not like this is described ? Strange to run tubes to outside of air cleaner element, thus inhaling dirt already filtered out and sitting there ? Just open to air then? sort of makes no sense—but maybe they did that? I think my 78 Dodge truck is vented inside the air filter at carb neck..but you might be correct. Very interesting about post engine shutdown vapors going in there, but if outside the element won’t they just fall out of air cleaner inlet ? oil gets in there , another thing described earlier. Why I think you are correct despite illogic, is that top of air cleaner comes off--- I think it takes PCV inlet hose with it.
I would expect PCV valves open at a certain vacuum, if so, probably same for all engines, so leans mixture slightly once running and when you adjust carb idle mix that air flow is involved / additive . I have often wondered if different calibration..I do not think it is an orifice but might be..or maybe both .Interesting thing , often wondered what it really does, One person told me it opens on high vacuum closed throttle decell, only, to flush out engine periodically , rather than steady leak. If only a check valve oil would not back up out of it….
Going to look more carefully at it…
Regarding charcoal canisters, these devices have nothing to do with the PVC system. Charcoal canisters are part of the fuel tank ventilation system and are designed to trap gasoline vapors that expand out of the tank. These fumes are also sucked into the intake manifold in a similar manner as the crankcase gases.
My ram 300K is equipped with an open PCV system and as Mike mentioned, I seem to recall that cars with multiple carburetors were exempt from the closed PCV retrofit.
Mandatory smog retrofits and biennial smog tests for cars 1975 and older ended around 1996 with Smog Check II regulations in California.
There is no filtration of the PCV air inside the air cleaner of our old Chryslers with closed PCV systems. Any dust collected with air wash absorbed by the engine oil in the crankcase. More modern cars now have a replaceable filter elements for the PCV system inside the air cleaners.
It seems reasonable to think that different engines had PCV valves with different orifice sizes, but I don't know for sure.
Good summary and all makes sense—except that part about the air cleaner “storing” residual gases from the crankcase after shutdown. I’m sure that was the state’s “logic” but the improvement over an open PCV system seems miniscule. At some point, the absurdity of an activated charcoal canister to capture these gases became mandatory. It probably works, but is it worth it? I hate the concept of “If it can be done, it must be done.”
I read you that our ’64 ram-engined 300K will not need to be retrofitted with a CA closed PCV system. Apparently, the law has expired. Hard to believe. Don’t tell anyone.
Still wondering if there is anything special inside a CA air cleaner to filter the air going out the nipple to the rocker-arm cover during normal operation—or to route the pickup point for the air to a point inside the filter ring. Otherwise, dusty air will be bringing particulate matter to be deposited in the rocker-arm cover—to be absorbed by lube oil. I’m pretty sure I have seen little air-filter media pads mounted inside the air cleaner to filter the PCV air. I also recall that PCV valves are calibrated to allow different air flows to different engines.
In the cold country, the PCV air will remain cold as it enters the air cleaner or vented oil fill cap. The cold air (or almost any combustion air) will contain moisture which will be converted to steam and be sucked out when the engine warms up.
From: kmaniak@xxxxxxx [mailto:kmaniak@xxxxxxx]
I think we all need a lesson in the history of the Positive Crankcase Ventilation (PCV) system so that we all have a proper understanding of the design and functionality.
Prior to 1961, the engines in our cars had a vent tube on the rear of on passenger side valve cover (V8 engine) to allow crankcase gases to vent to atmosphere. Typically these gases were clean when the cars were new, but as the engines aged, the crankcase gases became smoky in appearance. Cars with worn engines emitted smoke vapor from places other than the tailpipes. These fumes also contained unburned hydrocarbons and were quite smelly.
In order to reduce this residual polluted air coming from the engines, the PCV system was designed and installed starting in 1961. These first systems were referred to as "open PCV" systems. A hose was attached to a large manifold vacuum port on the base of the carburetor and attached to the PCV valve on the valve cover (the PCV valve replaced the old vent tube). Manifold vacuum pulled the crankcase gases out of the crankcase, through the PCV valve, to be burned with the air/fuel mixture. Make up "fresh air" was drawn into the engine through the vented oil cap. This system worked well as long as the car was running and reduced the emissions of unburned hydrocarbons by, say 95%. The only problem with this system was when the car was turned off. Residual gas pressure in the crankcase would escape into the atmosphere through the vented oil cap.
The state of California wanted a cleaner PCV system. This brought the advent of the "closed PCV" system, which was a legal requirement for all cars built for sale in the state of California (California cars) starting January 1, 1964. The "closed system" used a "non-vented" oil cap with hose nipple and an air cleaner cover with a matching hose nipple, and a hose running in between the two. With this design, fresh air was first drawn into the air cleaner housing, then into the crankcase through the hose and oil cap. When the engine was turned off, residual gases now collected in the air cleaner housing with less escaping to atmosphere.
Vehicles with the closed PCV system have an air cleaner housing with a hose nipple that is used in conjunction with the hose nippled oil breather cap and connecting hose. Vehicles with the open PCV system have an air cleaner without an air nipple and a vented oil cap, with a nonservicable, oil bath style filter built into the cap.
Up until the early to mid 1990's, California requires a mandatory retrofit of cars with "open PCV" systems to a "closed PCV" system. This retrofit was required for "out of state" cars brought into the state of California at the time the car was registered into the state. The retrofit was also required for automobiles currently registered in the state of California (registered before January 1, 1964) during a transfer of ownership.
The unsilenced air cleaner for the 360 hp 413 had a hose nipple attached to the side of the air cleaner top on "closed PCV" equipped cars. The silenced air cleaner used on all standard engine applications (361, 383, 340 hp 413) had the hose nipple usually attached to the air horn or the side of the top. Ram equipped engines may have had a hose nipple attached to one of the two air cleaners, and a hose nipple on the balance tube to suck crankcase air from the PCV valve.
Note - the PCV valve is a one-way check valve. Manifold vacuum keeps the valve open to allow air flow. However, should the engine backfire, causing pressurized air and possible flame to shoot towards the crankcase, the valve will close, preventing reverse flow back into the crankcase.
This should clear up most questions out there.
Chris the K MANIAC
The 1964 Parts Catalog lists only one air cleaner for the single-carb 1964 300K: 2463951 for VC2-300K, use w/Air Cleaner to Breather Pipe Hose. It lists an air cleaner for (single 4-bbl 413’s) NY’s & Imps that is silenced: 2402672. The 1965 Parts Catalog is similarly vague on the 413-equipped Chrysler 300.
The 1964 Service Manual states that the Closed Crankcase Ventilation valve is connected to the throttle body.
I don’t have anything to go by and am curious. Was there another supply-air hose running from inside the filter element on the air cleaner to the oil filler/crankcase breather cap so that only filtered air would enter the crankcase?
The 1964 Parts Catalog did show one special air cleaner California-only for Plymouths and Dodges with a 426 CID engine (not designated as a hemi)—and, also, designates two different RHS air cleaners for ram-engined 300K’s—with & without a connection to a Breather Pipe Hose.
So, for FirePower 360 HP 413’s--do we have silenced and unsilenced, CA and non-CA, same as NY & Imp? Pix of documented OEM air cleaners on FirePower 360 engines in and outside of CA would be helpful.
1961 was the first year for smog equipment on California sold cars. The 1961 Chrysler service manual shows the ram intake PCV valve.
Could it be that the smog regulations in CA started in 1965? With no snorkel, there would be no hose connection to a PCV valve. Would be interested in hearing from people in CA who would know when the regulations changed.
Posted by: "John Grady" <jkg@xxxxxxxxxxxxxxxxx>
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