[mklinger]

That filter has a diaphram in it, basically a one way valve. Under vacuum or zero pressure it remains closed. If crankcase pressure would exceed atmospheric it opens.
I suspect I would not have this issue with the 10's running to the air cleaner on my N/A motor but in other configurations, such as a boosted setup, if crankcase pressure built up and pressurized the the crankcase that breather would vent the pressure.

[wakesupremo]

Thank you. Makes perfect sense now.

[mklinger]

Have a look at this thread and the route I went.

https://forums.maxperformanceinc.com...d.php?t=864137

[HWYSTR455]

Reviving this thread, have two separate instances where there's excessive oil consumption in semi-fresh engines. Both cases are where it appears during high(er) RPMs on extended highway cruising.

mklinger - Why not just leave the valve covers vented in your draft setup?




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[GOAT8U2]

On all my sports cars, big 8 or 10an PCV fitting into a catch can then getting drawn on either by the Turbo inlet pipe or on my GTO the intake pulls on it through the can. With my Talon I added a 12v electric Star Machine vacuum pump that pulls 10" at WOT and I might add this on my GN. That'll add 2% power and stops all leaks from CC pressure.

The GTO doesn't get any real vacuum at WOT so it's sort of a dead system that only the dual breathers help at WOT. Even those lame smog pumps pulling 2-3" would help here.

[HWYSTR455]

True on not pulling vacuum at WOT, but those are usually short blasts anyway. You don't cruise down the highway at WOT for any considerable time.

I'm not against pumps, I just prefer not to because it's clutter in my opinion. If I had a dedicated track car, or one that sees a lot of extended WOT, I would do a pump.

The two cars that are experiencing pull-thru of oil show it on #7 & #8 plugs mostly. It's a little less than a qt every 3k miles, but it's enough to load the plugs up some. And I know the booster is good on both of them.



.

[Half-Inch Stud]

PCV positive CV. PCV uses a vacuum pull.

Makes me wonder about NCV; negative CV like No ventilation. Im easily confused.

Vacuum manifold pull, and Breathers on the Valve Cover really make the PVC positive. Factory vent tube into the air cleaner is close enough to he same. HIS

[Kenth]

At WOT valve cover breathers vents crankcase gases to the atmosphere (open PCV system) while the valve cover tube (closed PCV system) vents the same gases to the air cleaner for combustion.
At idle and cruising speeds the air goes into the crankcase thru the breather or tube.

[73ta]

Anybody running the two stage adjustable PCV valve. I am trying one currently.

[GOAT8U2]

Here's something I finally noticed after owning this car for 30 years......I don't have a rear main leak on my GTO anymore, I ditched the PCV and added a fitting so the crankcase is 100% always bypassing pressure. WOT is where you get the most blow by the rings to build crankcase pressure so this valleypan fitting will help, even though there's not much vacuum draw through the intake it's still getting some minor relief and the breathers can barely handle the rest.

The issue is a PCV that closes shut at WOT, you lose this as a crankcase vent and then you're blowing pressure out the dipstick and rear main. Dual breathers alone can't really handle 400ci+ to vent at WOT, we all generally have rear main leaks and we all go WOT a little or a lot.

The PCV is our issue, ditch this IMO and use the hole as a vent into a can with vacuum draw and you will be happy because you'll no longer putting a towel on your garage floor under your engine. Hahaha

[Kenth]

[QUOTE=GOAT8U2;6605723The issue is a PCV that closes shut at WOT, you lose this as a crankcase vent and then you're blowing pressure out the dipstick and rear main. Dual breathers alone can't really handle 400ci+ to vent at WOT, we all generally have rear main leaks and we all go WOT a little or a lot.[/QUOTE]

Time for a leakdown test?
Sounds like your engine suffers from piston ring blowby.

[Schurkey]

Originally Posted by GOAT8U2

Here's something I finally noticed after owning this car for 30 years......I don't have a rear main leak on my GTO anymore, I ditched the PCV and added a fitting so the crankcase is 100% always bypassing pressure.

Mistake in logic. The PCV system has two "vents", (the PCV valve itself, and the "fresh air inlet" which doubles as an outlet if there's crankcase pressure.) The "fresh air inlet" is ALWAYS open to the atmosphere, or to the air cleaner housing. Either way, if there's pressure in the crankcase, it gets vented.

Originally Posted by GOAT8U2

WOT is where you get the most blow by the rings to build crankcase pressure so this valleypan fitting will help, even though there's not much vacuum draw through the intake it's still getting some minor relief and the breathers can barely handle the rest.

I think your engine has excessive blow-by, if the breathers can "barely handle" that amount.

Originally Posted by GOAT8U2

The issue is a PCV that closes shut at WOT, you lose this as a crankcase vent

Not true. The PCV is fully-open at WFO, but there's little vacuum to pull the fumes.

Originally Posted by GOAT8U2

and then you're blowing pressure out the dipstick and rear main. Dual breathers alone can't really handle 400ci+ to vent at WOT

Again, if you've got more blow-by than DUAL breathers can accommodate, so that the crankcase has enough pressure to force oil out the rear main, or pop the dipstick up out of the tube, your engine needs help. Fix the excessive blowby, and the PCV system is good-to-go if it's in proper operating condition.

[Half-Inch Stud]

Most of my prior 455s had no blowby idle thru rpm. Those definitely had a PCV hose to the intake, and some had a Valve Cover Breather.

My last 455+060 in the Black 68 GTO stayed remarkably dry yet started-out with a rear Main leak that fixed itself after a few years.

Since early 80's had a couple 428 455 builds with blowby under load. And 1 of them had blowby at idle. The idle blowby is a real bummer that warrants a redo.


Is why if i go into a dry Build ( rods upgrade, etc) i reuse the rings and donta touch the CYLs.

[Tandyman]

A PVC valve actually restricts flow at high vacuum and is open at WOT.
This is how a PVC valve works

https://comtires.com/blog/auto-repai...-of-a-bad-one/

Glenn