Oil Cap / Crankcase Breather Q

My '69 EB with the 170 CID straight 6 has an oil filler cap that also acts as the breather for the crankcase. Problem is, it causes oil to get on my valve cover on down. Not bad, but bad enough. I'm wondering if anyone has come up with a way to make a separate breather tube or if there's an aftermarket available. I've got an idea to make something, but if there's a better idea already available, I'd rather do that. Thanks for any input.

Hi 'berg..,

There should be a PCV valve on the valvecover as well.

No oil should come out the breather cap riser tube. There should be a foam., or horsehair/hogshair media in the breather cap.

Oil shooting out that hole could indicate high case pressure "blow-by" (weak rings). This breather is mainly an air inlet.

Check that the PCV valve is working/hooked up properly.

Lastly., if the oil drain-back in the head got plugged...the rocker shaft area under valvecover could be filling up with oil..?

I was wondering about blow-by, but my dad rebuilt the engine several years ago & it doesn't seem to use much oil. It certainly doesn't have many miles on it. I haven't checked the compression tho. I did some surfing & found a later replacement valve cover that looks like it uses a twist-on oil cap. It's about $30 & chrome to boot. I run a couple of airport refuelers with 370s in them & they use a twist-on oil cap with a breather hose on it. That may be the simple answer there as I don't plan to tear it down & do a ring job no more than I drive it. I hate to disagree with you, but in my near 30 years of being an airplane mechanic, I've never heard of a breather being an INLET. It's an OUTLET for crankcase pressure. Unless we're talking about 2 different things but calling them breathers. If I change the valve cover, that's definitely the time to check the drain too. I didn't even realize this old of an engine used a PCV valve either, so I'll give that a check. Thanks.

famvburg said:

I was wondering about blow-by, but my dad rebuilt the engine several years ago & it doesn't seem to use much oil. It certainly doesn't have many miles on it. I haven't checked the compression tho. I did some surfing & found a later replacement valve cover that looks like it uses a twist-on oil cap. It's about $30 & chrome to boot. I run a couple of airport refuelers with 370s in them & they use a twist-on oil cap with a breather hose on it. That may be the simple answer there as I don't plan to tear it down & do a ring job no more than I drive it. I hate to disagree with you, but in my near 30 years of being an airplane mechanic, I've never heard of a breather being an INLET. It's an OUTLET for crankcase pressure. Unless we're talking about 2 different things but calling them breathers. If I change the valve cover, that's definitely the time to check the drain too. I didn't even realize this old of an engine used a PCV valve either, so I'll give that a check. Thanks.

Click to expand...

your right , outlet, and no pcv, if your blowin oil you know what to do your a mechanic LOL

BWY

"I hate to disagree with you, but in my near 30 years of being an airplane mechanic, I've never heard of a breather being an INLET. It's an OUTLET for crankcase pressure."

---Check me on this---

Eons ago., engines had a "breather-tube" out-n-down the back of the engine. These usually leaked out smoke when the eng. had time on it.

WALA..!! This created the invention of the PCV (Pos. crankcase vent.) This valve "sucks" that nasty smoke/air into intake to burn it.

Thus, eliminating any need for any "outlet" for case pressure.

Oil filler tubes also relieved pressure. Smoke fr. there was an indication of a run-out eng.

With the installation of a PCV valve..., the oil filler tube is now, an air inlet tube for the most part.

I believe the engines of today are completely sealed...??

ALSO., when I look down my oil filler tube., I can see the rockers. i.e. not even a baffle in there..... & I get "0" oil out that tube.

AND, my spare eng. '83 I-6 200 has a PCV at the front of the valve cover., & a "sealed" cap at the rear for oil inlet. Oddly it has a baffle.

FWIW., PCV came out in the early 60's as a "kit" to be installed by owner. Shortly after., they came on the veh. fr. the factory.

Sorry bully I am sure you just mistyped

No oil should come out the breather cap riser tube. There should be a foam., or horsehair/hogshair media in the breather cap.

Oil shooting out that hole could indicate high case pressure "blow-by" (weak rings). This breather is mainly an

'air inlet" from previous post from bully