Valve cover breathers/ crankcase evac systems

[FastEddie59]

What have any of you found that works well on these open cars for valve cover breathers? The open ones eventually become filled with enough oil that they blow back on the firewall and windshield and you, and all over the valve covers too. I installed the Mr. Gasket ones with the vacuum attachment and they are so restrictive that they will not pull vacuum through them and do become saturated with oil and leak at the crimped seal and blow oil all over too, might have caused intake end rail gasket to blow too from crankcase pressure build up. Before I get all the you have a problem responses it does not have a blow by problem and yes I have done a compression check and all is fine. It's just a very high performance SBC that makes 1.5 hp per cubic inch and there is no oil consumption between changes. I have considered going to an electric vacuum pump based system but that seems like overkill for street usage and know there should be something out there that works that doesn't cost a fortune, I am using the Brodix tall cast aluminum valve covers and they are non baffled, have to use them for roller rocker and stud girdle clearance. It is an uphill battle when you are fighting being in the open air and have to fight it blowing anything that comes out going everywhere! Any success stories are welcomed!

 

[RPM]

You did not make any mention of a PCV, does it have one? If not it needs one.

 

[Mike]

RPM has called it. Use a baffled grommet for your breather and then run a PCV valve on the opposite side. Plumb the PCV valve to the manifold, so you are not fouling the baseplate of the carb up with oil vapor.

 

[Johnny]

RPM has called it. Use a baffled grommet for your breather and then run a PCV valve on the opposite side. Plumb the PCV valve to the manifold, so you are not fouling the baseplate of the carb up with oil vapor.

Mike,
Should all PCV valves be plumbed to the manifold, or are you talking about this example only?

 

[Mike]

Should all PCV valves be plumbed to the manifold, or are you talking about this example only?

I don't like the concept of passing oil vapor through a carburetor. I've seen some carbs come off vehicles with excessive leakage that will gum up the base plate to an incredible degree.

 

[Rick]

Mike,
Should all PCV valves be plumbed to the manifold, or are you talking about this example only?

What Mike means is if you go to the carb.on most cars the oil in the fumes will leach out through the gaskets and stain the carb base plate.Where as the manifold deal will discharge the mist directly into the engine.

 

[Ted Brown]

I tried using breathers mounted to the bottom of the valve covers, ONCE. and never again, mounted them to the top side edge, and installed a baffle inside the valve cover to keep the oil from ever touching the holes leading to the breathers... open at the bottom of the baffle plate or shield as you may call it...

 

[Northstar T]

I had problems blowing out the seal under the intake manifold on a strong 377 SBC in my off topic car until I swapped out the 3/8 hoses used for the PC valve plumbing with 1/2" . run a 1/2" hose from the air filter box down to the valve cover instead of using an open breather. cleaner air and less mess IMHO.

 

[PotvinGuy]

I took the PCV valve out of the breather, epoxied in a disc with a pinhole (this has been done by some carmakers, they call it a "calibrated orifice"), and ran the hose to the manifold. This ensures the engine is always sucking the crankcase. The pinhole is about 1/16"; don't make it so big it affects the idle or fouls the plugs. I don't trust aftermarket PCV valves; they only work in certain orientations, and only open above an unspecified manifold pressure that your engine may or may not develop in routine driving. One size does not fit all :nod:

 

[FastEddie59]

You did not make any mention of a PCV, does it have one? If not it needs one.

Technically I would guess that the breathers are PCV's since they do have vacuum attached to them, decided to gut the Mr. Gasket breathers, put a sized opening in them for restriction and go top a vented puke tank in a good airflow area to pull a vacuum when air passes over it and plumb breathers into it and can check drainage to determine if I need to modify the opening in the breathers, and I'm going to stay with the baffled grommets so it will make it more difficult to pull oil up into them, thanks for the suggestions.

 

[FastEddie59]

I had problems blowing out the seal under the intake manifold on a strong 377 SBC in my off topic car until I swapped out the 3/8 hoses used for the PC valve plumbing with 1/2" . run a 1/2" hose from the air filter box down to the valve cover instead of using an open breather. cleaner air and less mess IMHO.

Mr. Gasket breathers do use a 1/2" hose

 

[PotvinGuy]

Mr. Gasket breathers do use a 1/2" hose

FastEddie, are you using two breathers with hose attachments? Only one breather should have the hose attachment. The other breather is the "intake", fresh air passes thru the crankcase and exits thru the breather with the hose attachment.

 

[Mike]

The primary cause of the problem on SBC is the fact it is nigh on impossible to locate a breather on the valve cover so you won't have at least one pushrod pumping oil directly at the bottom of the breather.

Moroso offers a couple of different baffling options for breathers that will knock down the worst of the problem.

This baffle (P/N 68790) is simple enough to install, just drill the holes and bolt it on -

If drilling holes is too difficult a project, then use these grommets (P/N 68775) -

If you use the grommets, try to align the grommet slot vertically, to allow maximum drain back out of the grommet.

This is one of those areas where examining all the purchase options before buying any parts can make a big difference. Rather than dropping the money on a set of stud-mounted roller rockers and a stud girdle, look into a set of shaft mounted rockers. The Jesel Sportsman Series work a treat and the price is still within reason.



The combination is made to bolt to a stock cylinder head without any modifications and has the advantages of eliminating stud deflection and the need for stud girdles. If replacement of a valve spring becomes necessary, simple unbolt that pair of rockers, change the spring and torque the rockers back to the bar. 99 times out of 100, you will find valve lash will be right where you left it, without the need to reset anything. And the combination will fit under a lot of stock-height valve covers, to boot.