Breather vs. PCV

I always remember breathers being located on the driver's side.

Keep in mind the oil filter and the pump are on the driver's side front and if you are pulling fumes from there as opposed to the rear of the passenger side, you might not be pulling "through" the whole motor

all theory on my part, I wouldn't make any decisions based on my statements

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A breather creates a vacuum leak and unmetered air going into the engine. Yes it was done that way in the 70's. That in itself doesn't make it proper. In those days the engine was tuned for the vacuum leak. The breather setup changed for a reason and it wasn't just for emissions.

ALL modern engines including the 302 prior to be discontinued run a PCV system with negative crank case pressure for a good reason. I don't remember any of them having issues with gaskets sucking in.

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A breather creates a vacuum leak and unmetered air going into the engine. Yes it was done that way in the 70's. That in itself doesn't make it proper. In those days the engine was tuned for the vacuum leak. The breather setup changed for a reason and it wasn't just for emissions.

ALL modern engines including the 302 prior to be discontinued run a PCV system with negative crank case pressure for a good reason. I don't remember any of them having issues with gaskets sucking in.

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Beg to differ.....

When the PCV valve is in the valve cover and the other cover is capped there is very little air being pulled through the PCV valve. It is pretty much a closed system.

On a "not wore out" engine even the smallest of vacuum to the valve covers will eleminate the oil smells and other slimyness under the hood.

Check out the engine of any new engine and you will see a plastic tube going from the valve cover to the intake plenum ahead of the MAF. It is a modern PVC set up.

You can and we did up the HP with a vacuum pump. I never bought the idea that it "sucked" the rings in tighter - we used gas ported pistons and you can't get a better seal than that. My theory is that taking the air out of the block means less air having to be moved around below the the pistons as they move up and down and that means less work for the engine. Having the pump fail would cost us a tenth. That is fairly sizable.

I like road tubes as they coat the underside of your car with an oil mist and keep it from rusting. Kind of like a continuous Z-barting treatment.

(not really - they are stinky)

Paul

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Well,

I run a PCV valve on the passenger side and a breather cap from edelbrock on the driver side, is this wrong or doesn't matter?

I have under load a pretty bad oil smell under the hood and I'm curios is that the result from that breather cap.

Thanks,

Oskar

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it doesn't matter which side the pcv is on.

you can have it either on the driver's front, or the passenger rear.

The opposite side from the pcv should be a breather. it works the same if you use the original air cleaner side filter or a twist on breather cap.

basically the pcv system provides a few functions.

1) creates negative pressure which stops small oil leaks.

2) removes fuel vapor and moisture from the engine, this reduces oil varnish build up, reduces internal corrosion from water vapor.

3) increases oil life.

4) acts as a intake back fire arrestor. under certain situations the intake pressure can be higher then the crankcase the PCV valve closes to prevent reversal of the exhausted air back into the crankcase again, like sudden deceleration with engine load.

going back to setup.

ford put the breather on the rear passenger and the pcv with the oil cap on the drivers side. mostly due to the oem air cleaner design.

the hose connection on the passenger side to the air cleaner has a filter with a orange body and a clip that holds it to the cleaner. the filter is outside the normal carb air filter thus it sees normal atmospheric pressure, this makes it just like a breather, the filter prevents junk from getting sucked inside the engine when the PCV turns on when vacuum is high. the pcv turns off when vacuum drops. otherwise it would act like a vacuum leak. At idle when vacuum is over 12HG the valve is on. when you stomp the pedal and the vac drops it turns off. at cruise with steady vacuum over 15HG it stays on. you can see how a mild or wild cam in an engine could come in conflict with the PCV this is why higher Horsepower cars use 2 breathers instead of the PCV system. the PCV is a controlled vacuum leak.

so on the drivers side the pcv goes to full manifold vacuum;

Thus when the PCV is on, air pulls through the outside of the air cleaner, through the pcv filter down the passenger side, through the crankcase and up through the drivers side then directly into the intake of the engine. When the PCV shuts down during acceleration the engine sees normal atmospheric pressure, as the system stabilizes again Vacuum goes up and the PCV opens again.

the wrong PCV can also cause problems, if you have one that opens with low vacuum it will cause stalling, rough idle.

caution; most of us have aftermarket intakes and cams. it is recommended that you split the vacuum load on the intake. for example you have the brake booster usually running off the rear along with vacuum accessories, the PCV can create as much demand as a brake booster. so if you have everything off the rear of the manifold you will have a race condition where either the PCV or the brake booster will be fighting for vacuum capacity, this can cause all kinds of tuning issues and it will make the rear bank of the engine run lean because the fuel will fall out of aeration. So what you want to do is use the front intake manifold port for the pcv this way you equalize the vacuum usage in the intake manifold, and it equalizes the fuel/air mixture in the intake manifold better.

the direction of flow through the valve covers doesn't matter so long as you create the negative pressure in the crank case.

I ran with breathers only when i first got my car. let me tell you the difference of using the PCV was night and day as far as benefit to the motor i would highly recommend using the PCV system if you can.

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