BBC Valve Cover Breather/Filter! WHY?

[savatreatabvr]

After I first got my truck I bought a pair of chrome BBC Moroso valve covers plus a Moroso breather/filter from some guy on Craigslist, I didn't realize it at the time but both valve covers have baffles in them. It's not a problem it just makes adding oil a real pain but what's the main purpose of a breather/filter and should I replace the factory oil cap with the Moroso breather/filter?

[Hazieview]

I would run a stock oil cap on one side and a pvc valve on the other.

Here is a description of a pvc valve and the reason it came stock on engines.
http://en.m.wikipedia.org/wiki/Crank...ilation_system

The breather caps just vent 'blow by gas' under the hood. The pvc valve keeps the gases contained and also maintains crank case pressure by pulling a vacuum from your intake.
It's what I'm running. Those breather cap things look too ricey to me... Just my opinion.. Plus I want all my exhaust gas leaving out behind me through my tail pipes, not my engine bay. good luck!
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[savatreatabvr]

Ok, so that's the reason I mainly see valve cover breather/filters on cars with open headers like Sprint Cars and Super Modifieds.

[Cue-Ball]

You need to have some sort of vent/breather on an engine. As the pistons compress the air/fuel mixture there is always a little blowby, even in a perfectly running engine. That little bit of blowby multiplied by 8 cylinders multiplied by thousands of RPM adds up to a large volume of gas entering the crankcase. So, you either have to vent it or suck it out. PCV is the preferred method because it gives you a chance to re-burn those fumes as well as creating a vacuum inside the crankcase. In the case of sprint cars and such, they tune their carbs and ignitions to run in a very narrow power band and it's easier to not introduce variables such as the PCV (or mechanical/vacuum timing advance, etc). You're better off running a PCV in a street car/truck.

[savatreatabvr]

I'll keep the PCV and I'm assuming to not replace the factory oil cap on the other valve cover with the breather/filter?

Originally Posted by Cue-Ball

You need to have some sort of vent/breather on an engine. As the pistons compress the air/fuel mixture there is always a little blowby, even in a perfectly running engine. That little bit of blowby multiplied by 8 cylinders multiplied by thousands of RPM adds up to a large volume of gas entering the crankcase. So, you either have to vent it or suck it out. PCV is the preferred method because it gives you a chance to re-burn those fumes as well as creating a vacuum inside the crankcase. In the case of sprint cars and such, they tune their carbs and ignitions to run in a very narrow power band and it's easier to not introduce variables such as the PCV (or mechanical/vacuum timing advance, etc). You're better off running a PCV in a street car/truck.

[Hotrodrobert]

Best is a baffled PCV on one side and some kind of filter on the other. The PCV won't pull oil out if it is properly baffled and the blowby isn't too much. The filter filters the air going through the engine and into the PCV. The filler cap just needs to plug the hole in valve covers that have some source for air management already, like stock, but you really need air in one side and out the other.
By having air in one side and out the other you pull most of the contaminants out through the PCV. If blowby is excessive, it can vent through the filter side.

[TJBrown]

On our race cars we run vacuum pumps on them with no filters. On my Dragster i usually run 12 to 13 inches of merc on my engine as i run Alcy on it. This does two thinks. Gets you better ring seating and also keep the engine from non pressurized leaks while running.

[savatreatabvr]

No kidding, is there any way to rig up something like that on a street vehicle?

Originally Posted by TJBrown

On our race cars we run vacuum pumps on them with no filters. On my Dragster i usually run 12 to 13 inches of merc on my engine as i run Alcy on it. This does two thinks. Gets you better ring seating and also keep the engine from non pressurized leaks while running.

[savatreatabvr]

Some people say no No NO on replacing the factory oil cap with a breather/filter but I'll try the breather/filter for a few and see what happens because what you said made perfect sense.

Originally Posted by Hotrodrobert

Best is a baffled PCV on one side and some kind of filter on the other. The PCV won't pull oil out if it is properly baffled and the blowby isn't too much. The filter filters the air going through the engine and into the PCV. The filler cap just needs to plug the hole in valve covers that have some source for air management already, like stock, but you really need air in one side and out the other.
By having air in one side and out the other you pull most of the contaminants out through the PCV. If blowby is excessive, it can vent through the filter side.

[motornut]

if your getting a lot of blow by the oil will show down on the block under the filter
mine does

i've seen them vented to headers with special pipes to feed into the headers,
i think thats what they were for

[TJBrown]

Originally Posted by savatreatabvr

No kidding, is there any way to rig up something like that on a street vehicle?

Yes, it is pretty easy actually, Moroso sells the vacuum pump and you run a fitting into one valve cover. Other other valve cover has an adjustable valve. This valve is where you regulate the vacuum. Everything is connected with Steel Braided line with the rating on the vacuum. Ohhh and you have an oil air seperator that runs off the vacuum pump also. I many have some pictures of my setup on my dragster. Will look at lunch.

[hatzie]

Originally Posted by TJBrown

On our race cars we run vacuum pumps on them with no filters. On my Dragster i usually run 12 to 13 inches of merc on my engine as i run Alcy on it. This does two thinks. Gets you better ring seating and also keep the engine from non pressurized leaks while running.

Careful. Race and street engines are very different critters.

A race engine has a relatively short lifespan. Maybe equivalent to 10,000 or 20,000 miles. It won't ingest enough dirt in that time to cut it's useful lifespan.

A street engine that's expected to run at least 100,000 miles should have a filter to keep the air entering the crankcase clean.

Here's why. Look at the dust and crud in the air and PCV filter that was run on a street engine for 20,000 miles. The crankcase breather has the same air source. Without a filter that same kinda crud will be sucked into the bottom of your engine with the oil. It's a cascade failure from there.

Most of the crud won't make it to the PCV to grind up the rings and cylinders from the top. It's gone through an oil bath air filter called the crankcase. Most of that fine dusty crud will stick to the oil as the air passes by. It'll wash down into the pan with the return oil to grind up the oil pump. It can then fill up the paper in the oil filter forcing the filter into bypass mode so it can chew up the crank bearings, cam, lifters, cylinders... you get the picture.

[savatreatabvr]

Got the picture, so I should replace the oil filler cap on the valve cover with the breather/filter and leave the PCV on the other valve cover alone?

Originally Posted by hatzie

Careful. Race and street engines are very different critters.

A race engine has a relatively short lifespan. Maybe equivalent to 10,000 or 20,000 miles. It won't ingest enough dirt in that time to cut it's useful lifespan.

A street engine that's expected to run at least 100,000 miles should have a filter to keep the air entering the crankcase clean.

Here's why. Look at the dust and crud in the air and PCV filter that was run on a street engine for 20,000 miles. The crankcase breather has the same air source. Without a filter that same kinda crud will be sucked into the bottom of your engine with the oil. It's a cascade failure from there.

Most of the crud won't make it to the PCV to grind up the rings and cylinders from the top. It's gone through an oil bath air filter called the crankcase. Most of that fine dusty crud will stick to the oil as the air passes by. It'll wash down into the pan with the return oil to grind up the oil pump. It can then fill up the paper in the oil filter forcing the filter into bypass mode so it can chew up the crank bearings, cam, lifters, cylinders... you get the picture.

[Cue-Ball]

Quit making things more difficult than they need to be. Run a PCV on one side and a filler cap on the other and call it a day.

[savatreatabvr]

That will cure my issues? That's the way it's set up right now!

Originally Posted by Cue-Ball

Quit making things more difficult than they need to be. Run a PCV on one side and a filler cap on the other and call it a day.

[Cue-Ball]

Cure what issues? Your original post was simply a question about breathers. So far I havent seen you mention an actual problem.

[savatreatabvr]

I've started other threads detailing my BBC issues like it not idling correctly, running rough, fouling spark plug, running worse after valve adjustment, smoking after idling a while. I guess my 1976 454 has a lot of issues but it runs much better thanks to all of the excellent responses to my threads! Next is replacing the valve seals with the head still on, I'm just waiting for a break in the weather before I tackle it!

Originally Posted by Cue-Ball

Cure what issues? Your original post was simply a question about breathers. So far I havent seen you mention an actual problem.