Valve covers

Question: do I need a breather port on passenger valve cover?

Drivers side valve cover...one port for vacuum line.

Passengers side...one for breather one for fill cap.

Trying to find better than factory thicker aluminum cover...I'm on my third factory warranty set and keeps leaking...but all I find seem to have only one port in each side...

For proper ventilation of the crankcase you really should have a breather port in addition to the port that connects to the intake. Ideally, the breather port should be located diagonally across from the PCV valve port.

This arrangement provides for the most effective scavenging of the combustion gases and moisture that develop within the crankcase.

They must sell a vented oil fill cap/cover - don't they?

There needs to be a vent to atmosphere - to allow a free flow of fresh air into the crankcase to replace what is removed by the PCV system.

Without an atmospheric vent, and with the intake system constantly pulling a vacuum on the crankcase via the PCV valve/hose, the pressure in the crankcase will soon turn negative. This negative pressure will cause even more blow-by of combustion gases across the piston rings and into the crankcase.

Blow-by gases contain moisture and acidic vapors. These will condense and contaminate the engine oil. Eventually these contaminants will cause sludge to form in the lube oil system and crankcase walls.

my question would be you going thru so many new ones, is this....

are you tightening them too tight? How tight do you bolt them down?

what type gaskets? cork or rubber?

using any type of glue on them?

have the spreader bars on them?

I am not...the dealership has done it as the engine is still under warranty.

Have you tried a set of Felpro's PermaDry gaskets?

I switched to PermaDry gaskets (for both valve covers and oil pans) about 8 years ago. They have proven to be outstanding. I would never use any other type.

They seal perfectly from the beginning, never have to be re-torqued and can be reused over and over.

Honestly, because of the PermaDry line, I had kind of forgotten all about leaky valve covers and oil pans. Reading this brings it all back - Jeez, what a pain in the ass they were to deal with.

Where do I find the better covers? I'd like cast aluminum but cannot fine one with two holes in it....

I think maybe you are getting hung up on the 2 hole feature.

On the LH side you need one hole - accepts the PCV and is generally located close to the front. Allows for easy connection from the PCV to the intake.

On the RH side you still only need one. Yeah, I know what you are going to say, and you are right. There always used to be 2 holes - one for a breather and another for an oil fill cap.

But think about it - the same single hole can be used for PCV inlet air and as an oil fill.

Index the valve cover so that the hole is near the back (for more effective removal of crankcase gases).

Buy an aluminum breather cap and install it in that hole. It will provide an opening to atmosphere and allow fresh air in as required by the PCV system.

Then, say one day you check your oil, and find that you need to add a quart.

Holy crap! Now what? How the hell are you going to get the oil into the engine? You should never have listened to that idiot chengny guy!

Seriously, just pop the breather out and pour the oil in. But go slow, often these single hole valve covers have de-misting baffles under the opening. If you pour the oil in too fast, it will back up and flow out all over the valve cover - and down on to the manifold.

When the oil is in the engine, pop the breather back in the hole and drive away.

Unless I am missing something, I think that you may be over analyzing this. If 2 holed valve covers for the RH side were necessary to operate a Chevy 350 - and they were not made or sold anymore - there would most likely have been a public outcry.

One last question; I assumed from the beginning that these are perimeter bolted valve covers you are having trouble with (not center bolt style) - correct?

Mr Gasket Ultra Seal gaskets work great too.

As was said, all that is needed is one hole in each cover. One side gets the rubber grommet with the small hole for the PCV, the other side gets the grommet with the large hole for a push-in style breather. The breather doubles as your fill cap since it has the larger opening in the grommet.

Eldelbrock has a set that comes with the baffles and just do as chengy suggested and put a breather fill cap on one side.

chengny said:

Without an atmospheric vent, and with the intake system constantly pulling a vacuum on the crankcase via the PCV valve/hose, the pressure in the crankcase will soon turn negative. This negative pressure will cause even more blow-by of combustion gases across the piston rings and into the crankcase.

Blow-by gases contain moisture and acidic vapors. These will condense and contaminate the engine oil. Eventually these contaminants will cause sludge to form in the lube oil system and crankcase walls.

Click to expand...

Actually, that is somewhat incorrect. A vacuum pump attached to a sealed crankcase will actually create a better ring seal, and eliminate blow by. Blow by is oil making it past the rings and into the combustion chamber. This of course causes more of the nasty stuff you mentioned present in the crankcase, and is not good fit a street driven engine.

Aahh - I don't usually debate - because there are so many different (but still correct) schools of thought on virtually any engineering subject. But just to offer another perspective:

The use of a vacuum pump, or any other means to create an augmented crankcase vacuum only improves (ring face to cylinder wall) sealing in applications where low tension ring packs are used.

These rings are flexible and loosely fitting enough to allow them to react to the increased pressure differential that results when crankcase pressure is reduced.

Assuming that the pressure on the inner ring surface is mainly a function of compression ratio and remains constant, the only way to increase the outward force of the ring against the wall is by reducing the pressure on the outer side of the ring surface.

So, while it is true that low tension rings are able to take advantage of this greater delta P, the same cannot be said of a stock Chevy ring pack. As designed, stock rings do develop some outward force due to the pressure of combustion but not nearly what LT rings can achieve. They are just too thick across (5/64" on the compression rings and 3/16" on the oil control ring) and too rigid, to react like low tension rings.

And this is assuming that the stock rings and cylinder walls are in factory condition. But as the engine ages normally, the walls and ring faces wear and the original tight clearances begin to increase.

At some point, the ring to wall clearance hits the tipping point. It should be noted that; just like any other fluid, the pressurized gases created by the combustion process will always seek the path of least resistance. Eventually, due to the increased clearance/loss of tension between the cylinder wall and the ring face, the path of least resistance shifts. Now, more of the combustion gases start to leak by the outer faces of the rings instead of being captured behind them.

And (Boy, it took a long time to get here) was the basis for my comment:

Without an atmospheric vent, and with the intake system constantly pulling a vacuum on the crankcase via the PCV valve/hose, the pressure in the crankcase will soon turn negative. This negative pressure will cause even more blow-by of combustion gases across the piston rings and into the crankcase.

I was working on the assumption that the OP had a stock SBC with 100K miles (or so) on it. In that case, I still believe that the increased delta P created by the lack of an intake air vent will result in greater quantities of combustion gases leaking past the rings and entering the crankcase atmosphere.