Oil coming from breather

[ian75c10]

hey guys I have a 1967 327 that has the oil breather on the passenger side by the firewall end of the valve cover and the pcv hose to carb vacuum is located on the drivers side from of valve cover. Is this correct and would it matter if it was the other way around for any reason. Lots of photos online show this switched the opposite way from how they set up on my engine. Also I am getting oil blowing out of the breather and making a mess. i dont believe i over filled it with oil. I didn't notice all thow the breather stays in place it is not all that tight, only snug. thanks

[enaberif]

Check your pcv valve to ensure its working properly and yes you are setup properly.

[rich weyand]

Yeah, that's an OK setup.  That's how mine is as well.

Check that your PCV valve is OK.  They sludge up and then stick shut.  All you need to do is pull it out and shake it.  No need to remove the hose.  Just shake it up and down.  If it rattles, it's OK.  If not, replace it.

[ian75c10]

Thanks so much, just did the shake test and yes it did rattle nicely. There is a bit of oil residue around that pcv valce on the valve cover as well. its just much more on the other side by the breather. Do those breathers clog up and go bad too? I dont know how old this one is. Its the simple style chrome cap push in. are the fancy ones better?

[rich weyand]

No, fancy ones aren't better.  They do clog up with guck, just like an air cleaner.  If it's more than a couple years old, replace it.

[Engineer]

How many miles are on your 327?

It could be that the rings, especially if they are originals, are giving up their ability to seal.

If your 327 has the original intake it should have a pipe sticking up from the front of the intake with a vented cap that just pushes on. That is where you would fill the engine with oil, and vent the crankcase. It wouldn't have came with a PCV valve.

If your 327 has a PCV system it is a later addition. I like the PCV system. It keeps the combustion gasses (exhaust) out of your engine. Without the PVC system the inside of your engine will look like the inside of your mufflers after time, this also contributes to the black oil that older engines are famous for. The main draw back to the PVC system is that the exhaust your PVC system vacuums out of the crankcase makes a mess of the carburetor. So, on an older engine this area is likely to become clogged.

[Oldchevguy]

Any idea how many miles on your 327?. Sounds like blow by, compression leaking by the rings and pressurizing the base. That blow by leaks out of the base of the engine however it can, in this case up through the oil drain holes that return oil from the heads back to the oil pan.

  The leaked compression or blow by carries oil vapor with it as it rushes to get out of the engine and this accounts for the oil coming out on your valve cover around the breather filter.
   
  Normally the breather filter's job is to filter the fresh air being drawn into the engine by the PCV (positive crankcase ventilation system) and the PCV's job is to pull the normal accumulation of gas and oil fumes into the carb to be burned off.
         
  Most of these breather filters are just a meshy type of material inside a canister that plugs into the valve cover or a plastic unit that fits inside a full size air breather.

  At idle the engine vacuum is maxed out and the PCV works at max vacuum. When you open the throttle the engine vacuum is reduced and you also have more blow by because that increases the harder the engine works so the extra pressure carrying oil vapor with it leaks out of the engine where ever it can.

At wide open throttle there is virtually no manifold vacuum so and lots of blow by with a worn engine so when you need the PCV the most it works the least. Most oil vapor leakage happens here and even if you sealed up the PCV holes the engine would still leak from the next weakest gasket because of build up of blow by  pressure.
   
 In the old days I have run small blocks that were so worn I just hooked a piece of heater hose to the valve cover and ran it down under the truck to get rid of the oil vapor and the smell and add lots of oil!
 
To test your engine warm it up good and pull PCV valve out of the valve cover, how much vapor comes out the PCV hole. Some is normal but how much does it increase as you speed up the engine? You can always compare your engine to a known good engine to get an idea. If blow by puffs out of the PCV hole then a compression test and further investigation are needed.
Good luck.

[Dirka]

I'm having the same problem on my 400, I thought maybe it was because my valve covers didn't have baffles to stop the oil vapors from blowing up into the breathers.  The guy I had rebuild the engine said not to run a PCV and to just run 2 breathers.  I'm wondering now after reading what Oldchevyguy had to say, if I didn't properly seat my rings in the beginning and thus now have bad ring seal and leaking that way??
Guess and leak down/ compression test is first place to start.