Why am I leaking so much oil from my breather?

[DarkoNova]

Brand new engine rebuild. I have a new PCV valve in the passenger side cover, with a baffle. I have a breather on the driver's side cover, with no baffle. The only reason I don't have a baffle is because I don't have any other place to add oil and it makes it SOOO much easier and faster to add oil. It leaks enough oil that there's a big mess on the top/front of the valve cover and there was even a couple drops on the sealing edge that were about to drop onto the header.

I didn't think I'd need the baffle on the breather side anyway since it should be pulling fresh air in. So why is it so oily???

[sgernon]

By chance do you have an issue with the location of the breather/PCV in the valve cover? I once used the older M/T or Holley aluminum valve covers and the holes for the breathers and PCV were on top of the cylinder and rocker arms which meant the rockers were squirting oil directly into the breathers. I changed to a newer valve cover and the breather holes are between the cylinders and not on top of the rockers. This stopped by oil issues.

[Tony_SS]

SBC?

My pvc is on the drivers side and is plumbed into the carb base to evacuate and recycle oil/fumes and on the pass side I have an open element breather. No oil issues...

[parsonsj]

1. Is your PCV connected to engine vacuum?

2. Remember at WOT, you make little or no engine vacuum, and create lots of blow by. In that case blow by will get pushed out the inlet -- even if you have the PCV connected to engine vacuum. The best PCV systems for hot rods have a catch can on both the inlet and outlet for that reason.

[DarkoNova]

1. Is your PCV connected to engine vacuum?

2. Remember at WOT, you make little or no engine vacuum, and create lots of blow by. In that case blow by will get pushed out the inlet -- even if you have the PCV connected to engine vacuum. The best PCV systems for hot rods have a catch can on both the inlet and outlet for that reason.

Yup, PCV is going to the big port on the front of the carb.

I want to run one of your catch cans, actually. I just don't have the money for one yet.

These are the valve covers I'm using:

https://static1.pt-content.com/images/pt/2012/04/pro141921_w-1.jpg

[Tony_SS]

I'm pretty sure the PCV should be on the drivers side, not the pass side.

[DarkoNova]

Interesting, I didn't think it even mattered.

Man, that means I have to swap the covers then so the PCV will have the baffle. -_-

[sgernon]

I have the PCV on my passenger side, it should not matter which side it's on with the excpetion of the baffle if you need it.

I don't really like the location of the hole for the PCV. It looks like the same issue I described. The hole appears to be directly above the pushrods and I assume they are shooting oil in the PCV/Breather hole. Compare that to the location of the hole on these covers. On these hole is between the rocker arms.

58602

[ehummelman]

I'm pretty sure the PCV should be on the drivers side, not the pass side.

Sorry, but it makes absolutely no difference which side you use. As long as you have one side drawing air out and the other letting air in you're fine.
Of course John Parsons is correct about WOT, but unless you're at WOT all the time I don't see why you would have all that much oil blowing out if the system is functioning correctly. Drag cars that are always at WOT actually just use a header evac system to draw out the fumes instead of a vacuum port precisely for the reason John mentioned.

is the oil coming out the breather element/mesh or at the seal? You may just want to try a tighter grommet if that's where it's coming out.

[Tony_SS]

Sorry, but it makes absolutely no difference which side you use. As long as you have one side drawing air out and the other letting air in you're fine.


Alright.. I wasn't sure about that.

[DarkoNova]

I don't really like the location of the hole for the PCV. It looks like the same issue I described. The hole appears to be directly above the pushrods and I assume they are shooting oil in the PCV/Breather hole. Compare that to the location of the hole on these covers. On these hole is between the rocker arms.

I didn't notice that. I hope I don't have to put the baffle back on because I hated filling the engine with oil with the old valve covers since they were both baffled.


Is the oil coming out the breather element/mesh or at the seal? You may just want to try a tighter grommet if that's where it's coming out.

Coming out at the seal. The breather is the one I was using in the old valve covers, and is at least a good 4 years old. Maybe the rubber shrank over time? The new PCV valve has a super snug fit, but the breather can wobble around a little. Hopefully if I get a new one it'll be a tighter fit. Guess I'll start by getting a new breather.

[ehummelman]

Hopefully getting a better seal will do it. Otherwise, there's too much crankcase pressure for some reason.