Small vid about PCV

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AJ/FormS said:
yabut., is that system gonna flow enough backwards at WOT after 13/14 seconds, to not blow the dipstick out.. or worse
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Not once has it ever shown any indication of needing to vent beyond the PCV.
Good question though.
 
I was pretty sure that you were aware that at WOT, CC pressure will build, which will slam the PCV shut, which will force the CC fumes to flow up into your breather and from there into the Air filter house. Usually those fumes will be oil-laden and make a mess in your housing.
But maybe your breather is acting as an oil-separator, which it should be, but heck, yours, since it keeps your line clean, is a really good one!
Nevertheless, if your PCV is stuck open, the CC fumes will pass into the intake under the carb, which is a no-no, cuz if the engine ever backfires with a closed throttle, the flames could enter the CC, and if they find a combustible mixture in there, you could be looking at a bomb.
But I think you knew all that.
 
Charrlie_S said:
OEM has been doing it like that since about 1963
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Not like that. It’s like AJ said. With a breather open to manifold vacuum when it drops at WOT any blow by will go right into the engine. The OE’s didn’t do that.

They have a breather that’s open to atmosphere so at WOT the blow by can go somewhere other than the engine.

IMO, the guy who made the video should have just blocked off the open breather all together and just let the PCV pull a vacuum in the crank case.
 
Newbomb Turk said:
Not like that. It’s like AJ said. With a breather open to manifold vacuum when it drops at WOT any blow by will go right into the engine. The OE’s didn’t do that.

They have a breather that’s open to atmosphere so at WOT the blow by can go somewhere other than the engine.

IMO, the guy who made the video should have just blocked off the open breather all together and just let the PCV pull a vacuum in the crank case.
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Beg to differ. Just an example Look in the mopar factory service manual (1972) section 25, pg 15 and 16, figure 4, under crankcase emissions. Hose goes to air cleaner. Only the very early PCV systems had a breather open to air.
The 1967 service manual shows the "Open to air " breather system for "federal" spec cars. But shows the "Closed" (hose to air cleaner) system for Calf spec cars. So I was off about 4 years on how long the OEM has been using the closed system. My memory is not what it used to be. (old age don't you know).
 
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Newbomb Turk said:
Not like that. It’s like AJ said. With a breather open to manifold vacuum when it drops at WOT any blow by will go right into the engine. The OE’s didn’t do that.

They have a breather that’s open to atmosphere so at WOT the blow by can go somewhere other than the engine.

IMO, the guy who made the video should have just blocked off the open breather all together and just let the PCV pull a vacuum in the crank case.
Click to expand...
Have you ever heard or read of vacuum stripping the oil out of bearings when running a sealed crankcase PCV?
 
Newbomb Turk said:
Not like that. It’s like AJ said. With a breather open to manifold vacuum when it drops at WOT any blow by will go right into the engine. The OE’s didn’t do that.

They have a breather that’s open to atmosphere so at WOT the blow by can go somewhere other than the engine.

IMO, the guy who made the video should have just blocked off the open breather all together and just let the PCV pull a vacuum in the crank case.
Click to expand...
Ford never used a valve cover breather that was open to the atmosphere, so their system is exactly like @TrailBeast outlined and worked fine.
 
AJ/FormS said:
yabut., is that system gonna flow enough backwards at WOT after 13/14 seconds, to not blow the dipstick out.. or worse
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If course it will, the breather and hose to the filter is OPEN
 
Newbomb Turk said:
Not like that. It’s like AJ said. With a breather open to manifold vacuum when it drops at WOT any blow by will go right into the engine. The OE’s didn’t do that.

They have a breather that’s open to atmosphere so at WOT the blow by can go somewhere other than the engine.

IMO, the guy who made the video should have just blocked off the open breather all together and just let the PCV pull a vacuum in the crank case.
Click to expand...
Either you are wrong or did not word this well. The system as pictured differs only in one way from some of the cars I've owned--My 69 383 RR for example, had the hose from the air filter bonnet to the breather, was on the DIRTY side of the filter. I don't even remember anymore, if the 6BBL 70 was on the clean side or the dirty side. The method pictured, is essentially how all OEMs were done for years
 
67Dart273 said:
If course it will, the breather and hose to the filter is OPEN
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You say that like it was a fact.
But that breather may be a sealed unit. and if it has a hose nipple on it, that is the norm. and so
The fact is that as engines age, they may produce a lotta blow-by, especially at WOT, and just a few seconds could blow that smallish line right off the air-cleaner, but if it was secured really well, then something else might blow, and the usual losers are the dipstick popping up, or the valve cover gaskets puke.......
but this one time, I had an engine that blew oil out the back somewhere and made a real mess.

Then I bought me a blow-by tester. and hyup,
Then I pulled that engine out, cuz it obviously needed rings.
 
Blow-by entering the engine, at WOT, when laden with oil, can produce or contribute to, detonation.
Most of my classic cars had that hose on the outside of the filter, and the filter-house had an oil-collection ring there, which had to be cleaned out periodically, on engines with hi-mileage.
 
67Dart273 said:
Either you are wrong or did not word this well. The system as pictured differs only in one way from some of the cars I've owned--My 69 383 RR for example, had the hose from the air filter bonnet to the breather, was on the DIRTY side of the filter. I don't even remember anymore, if the 6BBL 70 was on the clean side or the dirty side. The method pictured, is essentially how all OEMs were done for years
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Yeah, I could be wrong on that. I haven’t done a PVC system like the OE’s do it in so long I forget exactly what they are doing.

IIRC, the idea of the PCV was to draw in fresh air, pull that air across through the engine and out the PCV and then back to the engine to be burned.

Im sure there are variations on that. I know I don’t do a PCV any more without using some sort of catch can between the PCV and carb. Some might be surprised what kind of crap goes through that system.
 
Newbomb Turk said:
No
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I asked because I tried a sealed crankcase pcv with a fixed orifice (under the intake manifold) and had weird oil pressure problems. When I researched it I seem to remember finding others with the same issue, and an article from good source stating that’s what was happening. Of course I can’t find it now. Regardless I went back to the previous setup with a fixed orifice and a one way check valve and inlet air metered through the throttle body and all was well.
 
TT5.9mag said:
Have you ever heard or read of vacuum stripping the oil out of bearings when running a sealed crankcase PCV?
Click to expand...

I think if that was true then people running crankcase vacuum pumps would be having that problem like crazy...?
 
MopaR&D said:
I think if that was true then people running crankcase vacuum pumps would be having that problem like crazy...?
Click to expand...
I think that’s where the info I found came from. Maybe on YB where guys running vacuum pumps we’re having the issue.
 
TT5.9mag said:
I asked because I tried a sealed crankcase pcv with a fixed orifice (under the intake manifold) and had weird oil pressure problems. When I researched it I seem to remember finding others with the same issue, and an article from good source stating that’s what was happening. Of course I can’t find it now. Regardless I went back to the previous setup with a fixed orifice and a one way check valve and inlet air metered through the throttle body and all was well.
Click to expand...

I have heard of this with a vacuum pump on a wet sump. In fact, I think David Reher did a tech article on this way back in 2000-2001 or something in National Dragster.

There is truth in that dropping the crankcase pressure can (and will) drop your oil pressure some. I’m not sure you can pull enough vacuum through a PVC or even pan evacs (or both) to affect oil pressure.

The oil pump functions like any other positive displacement pump, in that a pressure differential is created in the gears and that pressure difference between the negative pressure in the pump (and by extension…pun intended…you’re welcome for that free funny pun) and atmospheric pressure in the pan. Or an even greater differential if you have some pan pressure.

Im not advocating for pan pressure. It’s bad. I’ll be testing my crap on the dyno hopefully by March, or April and I will see how much actual pan pressure I can pull with a PCV and pan evacs and where the greatest pressure drop occurs. I’m sure that will be at a light load, low throttle opening when both systems are working. But I won’t know for sure until I get a chance to test it.

Of corse, the way things go around here it could be June before I see the pump.
 
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