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Discussion Starter · #1 ·
Have a street/strip (mainly street) car, Since I put only 200-300 miles per year on car I do not run PCV (not like oily mist in combustion chamber). Question is would running a dual breather on one or even both VC hurt or help. Thought would get more air in or help get rid of gases. Not an engine guy so asking. Thanks!
 

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Cant hurt, as long as breathers baffled properly and they large enough to vent properly. One on each is fine especially if you dont rev 7k plus
Good oil control in oil pan is equally important especially with stroker 4.25 plus crankshat
 

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Have a street/strip (mainly street) car, Since I put only 200-300 miles per year on car I do not run PCV (not like oily mist in combustion chamber). Question is would running a dual breather on one or even both VC hurt or help. Thought would get more air in or help get rid of gases. Not an engine guy so asking. Thanks!
In my opinion you be better of using a PCV in one cover and a breather on the opposite cover, that is the way the system is designed to work. If your engine is in good working order (meaning no excessive blow-by) you will not get any oily mist in your intake tract or combustion chamber.

Easy to check.......just pull the PCV hose of, it should be nearly dry on the inside.
 
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I would run the PCV and a breather. Yeah it may put a little oil in the intake tract, though if the motor is sound it shouldn't. But otherwise 2 breathers will collect oil and leak. I would only use 2 breathers with the tubes running to the headers.
 
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On mine I run a PCV but have a catch can that the tube runs through so the oil is caught in the can before it gets to the carb. Check out Elite engineering or mighty mouse (which has a blow off breather) cans you will see what I mean. It can be a little complicated but I have a Victor Manifold so I have catch can where battery was and the lines go underneath the tarantula style runs to the front.
 

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Take a look inside your valve cover the next day after you've driven (especially when it's cold) it and you will see moisture in it.
If you don't want oil mist combustion chambers, install a air/oil separator inline with the pcv valve.
You will be amazed what it catches!
I did.
 

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All good answers to your question.

The GM 572 crate motor has two breathers with baffles. No PCV.

I run those exact breathers with the baffle tubes. If you always bring your engine to full operating temp you'll have less chance of condensation in the oil. It burns off.
 

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Discussion Starter · #8 ·
Decided to go back to PCV and see what happens. Next question, do I need to change any "settings" since PCV was put back in. I did check breather that I removed and see no oil in it but still gonna keep PCV in as local speed shop said also should have it due to str driving even though very little str use. Am using the baffle grommet since VC do not have a baffle on them. Been told also PCV will help move bad air out while breather letting good air in, better air flow? Thanks for the replies
 

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I don't have baffles in my valve covers and run a PCV without problems.
 

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Discussion Starter · #10 ·
Hopefully not looking stupid on this question, can I put a in-line filter between PCV and where it is connected to carb to help filter fumes or what oil may get into combustion chamber. Was wondering if one of those clear gas filters would work and just replace when I see it needs it. Still just edgy on using PCV and this stuff gets into motor. Car runs great using just breathers and hardly any oil in them anyway. See a lot of cars having evac system hooked to exhaust but to me no different than just breathers which i have at this time, fumes out exhaust or fumes out breathers but maybe smell under hood.
 

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With just breathers there is no fresh air being pulled through the crankcase, just gasses under pressure from blow by, etc. With PCV there is fresh air being pulled through the crankcase, thus flushing moisture, acids and gasses out and into your intake where they are burned. This is good for the engine, not gunking up your intake. Systems that are plumbed to the exhaust headers will pull a vacuum on your crankcase, this is beneficial for drag race engines because the lower pressure in the engine reduces drag internally. The tubes are wye'd into the header creating a venturi producing vacuum. If you go with a PCV valve, get the right one for your application as they are calibrated for different flows at various vacuum levels. You will have to adjust the idle if you add PCV. hope this helps.
 

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With just breathers there is no fresh air being pulled through the crankcase, just gasses under pressure from blow by, etc. With PCV there is fresh air being pulled through the crankcase, thus flushing moisture, acids and gasses out and into your intake where they are burned. This is good for the engine, not gunking up your intake. Systems that are plumbed to the exhaust headers will pull a vacuum on your crankcase, this is beneficial for drag race engines because the lower pressure in the engine reduces drag internally. The tubes are wye'd into the header creating a venturi producing vacuum. If you go with a PCV valve, get the right one for your application as they are calibrated for different flows at various vacuum levels. You will have to adjust the idle if you add PCV. hope this helps.
How do you determine which PCV valve to run?
Is it based off idle vacuum?
 

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Get a PCV for your specific application.

Honestly, this whole discussion really baffles me. If your engine is in good mechanical condition there should only be a minute amount of blow-by and you should NOT get any oil residue in your intake tract when using a PCV. If you have excessive blow-by no dual breather or catch can gizmo will fix that.....you'll have to rebuild your engine.
 
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Get a PCV for your specific application.

That sounds like the response I get from youngsters at parts stores these days.
Ask for a specific thing, and get the , year, make, model B.S.
OK.
Find one for this.
Look one up for a '65 Pontiac Lemans w/ 468 cid BBC that has 11" vacuum at idle.
 

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Here's a good read on PCV systems - http://mewagner.com/wp-content/uploads/2015/09/Engine-Professional-July_Sept-2015-p34_44.pdf. I select a valve based on obtaining the best idle. I've done this by selecting one that is specified for a factory high output engine that is the closest I can guess to what I have. For example - if my engine is built similar to an L78, then I get the valve for that engine and try it. If it's no good then try one for something else. I've awlays got one to work well, no idea if it is actually dialed in perfect, but good enough. Off the shelf valves may not work for all builds. The adjustable ones will cure your problem if you want to go down that road.
 

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Remember the old blow-by tubes and spooning out wax sludge of that rotten oil back in the old days.. Then gasoline with lead in it! It's a wonder us old gear heads are still here..

Put the breather in the passenger side and the pvc in the drivers side.. I forget why but there is a reason for this.. You could buy one of those breathers with the hose connection and run hose to the filtered side of the air cleaner...
 

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I've been running just breathers for years with zero issues. I have 2 per valve cover.
 

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Here's a good read on PCV systems - http://mewagner.com/wp-content/uploads/2015/09/Engine-Professional-July_Sept-2015-p34_44.pdf. I select a valve based on obtaining the best idle. I've done this by selecting one that is specified for a factory high output engine that is the closest I can guess to what I have. For example - if my engine is built similar to an L78, then I get the valve for that engine and try it. If it's no good then try one for something else. I've awlays got one to work well, no idea if it is actually dialed in perfect, but good enough. Off the shelf valves may not work for all builds. The adjustable ones will cure your problem if you want to go down that road.
Interesting bit of information.
For a performance engine it would seem screw the PCV and go vacuum pump.
 

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That sounds like the response I get from youngsters at parts stores these days.
Ask for a specific thing, and get the , year, make, model B.S.
OK.
Find one for this.
Look one up for a '65 Pontiac Lemans w/ 468 cid BBC that has 11" vacuum at idle.
Precisely, trying to tune around the extra vacuum leak that a PCV valve creates on a low vacuum engine is not good.

Better off using the Wagner adjustable version in these cases.
 
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