Oil Leak at Breather

Dan Stryffeler · #1 (**permalink**) 07-25-2006, 10:54 AM

It looks like the foam lining in the billet breather on my small block Ford is pretty saturated with oil which is now starting to drip out and leak on to the valve cover.

I have a pcv valve on the opposite side and was kinda under the impression that as gas would be pulled out of the engine through the pcv valve and burned off, that new air would be pulled in through the breather, but it looks like some bypas gas and oil are pushing their way up through the breather.

The fittings on each cover are baffled; pcv and breather units are from Billet Specialties... The pcv valve is currently plugged into the bottom of the air cleaner, maybe 2 inches away from the carb. I have a large oval air cleaner similiar to what would be used on a dual carb setup.

Does this imply that I am not pulling enough air through the pcv valve, or is it normal to have a certain amount of bypass through the breather also? The valve is new so I doubt that it is blocked.

I'm thinking that the air cleaner is so large that it is not drawing air from the pcv valve - relocate attachment to the carb instead?

Thanks,

Dan

nanard289 · #2 (**permalink**) 07-25-2006, 12:27 PM

Hi Dan
It could be a phenomenon due to an internal block pressure excess (piston compression leaks?). You have first to check your compression values for each cylinder. If one or some of them are too low, it is not a good omen. Good luck for your investigation

Dan Stryffeler · #3 (**permalink**) 07-25-2006, 01:38 PM

Yikes,

It never even dawned on me that this could be a compression issue... sometimes ignorance is bliss!

Thanks,

Dan

lnfletcher · #4 (**permalink**) 07-26-2006, 05:30 AM

Correct me if I'm wrong, but I thought the PVC hose needed vacuum to overcome the inherent ball valve inside it. My understanding is that it needs to be connected to the base of the carb or on the intake. If you have a regular breather without a pvc, then it can be routed to the oval breather. I had a simular problem with oil being forced from the dipstick and it was caused by (1) baffled grommets on the valve cover breathers (2) lack of a pvc.

trularin · #5 (**permalink**) 07-26-2006, 05:47 AM

At higher RPMs there is little vacuum and with high compression, "Let's go Charlie" speeds, there is blow-by that will occur. Valve seals and rings seal almost all, but not all.

I get blow-by that causes the breather to shed oil onto the valve cover. Makes a mess. I hit 8500 RPMs and I know there is bloe-by.

On top of that, roller rockers sling oil all over. If your baffles are open-ended, they are going to have oil slung up into the baffled area.

Keep your PCV system. My compression tests were all in the 180 to 195 range and the engine makes plenty of HP.

Just my opinion.

Roscoe · #6 (**permalink**) 07-26-2006, 07:34 AM

I had the same symptoms after running at high rpm. It was more annoying than anything else. I had a fitting welded onto my valve cover and ran a remote breather. Now as dry as a bone.

Roscoe

trularin · #7 (**permalink**) 07-26-2006, 07:45 AM

Roscoe, I am truely impressed. I wish I had done that.

Roscoe · #8 (**permalink**) 07-26-2006, 08:17 AM

It's never too late........

Roscoe

Dan Stryffeler · #9 (**permalink**) 07-26-2006, 10:20 AM

I'm going to try rerouting the pcv valve from the air cleaner assembly to the full manifold vacuum port on the carb base.

Will advise if it helps... thanks for all the feedback - appreciate it.

Dan

Roscoe · #10 (**permalink**) 07-26-2006, 10:24 AM

My pcv valve is plumbed to the back of my Demon carb and I've never had a problem there. I have on of those Billet Specialties pcv housings on the valve cover.

Roscoe

Burgs · #11 (**permalink**) 07-26-2006, 01:47 PM

Dan,

I set mine up the same way, with the pcv going into the bottom of the air cleaner, and after about 60 miles I've got oil on the valve cover with the breather. I'm guessing there is not as much vacuum thru the top of the carb, inside the filter, compared to under the carb. And as Trularin says, I have open ended baffles, and roller rockers, that don't help things. My Pro Systems carb has no vac port in the base, and I don't want to lean out a runner or two going into the intake, so a remote breather may be my solution.

Brad

Rick Parker · #12 (**permalink**) 07-26-2006, 09:12 PM

A manifold can be modified to house the PCV valve under the carb in the valley area, but the hose must be attached to a vacuum source within the manifold or to the base of the carburetor to function. Occasionally is was tied into an individual runner (not as desireable) because it caused that cylinder to run lean. There is not enough draw (vacuum) for the PCV to function if it is attached to the carburetor air filter. Each of the various PCV valves are manufactured with check valves within of varying weights which are engineered for different OEM applications, consisting of various cam timing, induction sizing, cubic inch displacement, and manifold design. The hose from the valve cover vent to the air filter allows filtered air to enter the crankcase through the hose attached to the breather (via the Carb air filter) and is then drawn into the intake system through the PCV valve. It is a closed sytem in its most advanced state.

trularin · #13 (**permalink**) 07-27-2006, 04:38 AM

I should point out that the PCV system is an evolved system. The first systems were very basic and had a breather much the same as those described in this thread.

However, some of us remember the "breather" element that used to be serviced on the air cleaner as a seperate filter. As you may recall; a car with engine setups where the owner felt the urge to hammer the throttle often had oil in the air filter and the breather was soaked.

This isn't anything that has not existed before.

Just an additional $0.02

Dan Stryffeler · #14 (**permalink**) 07-27-2006, 05:03 AM

Morning,

I re-routed the pcv valve to the base of the carb last night... it would appear that the idle pulled down a little indicating something is happening. I was only able to get about 10 miles on the car and no oil so far, but I cleaned out the foam filters in the breather so they may have a ways to go before oil starts coming out. The thermostat never dumped in those test miles so I have not really got the car warmed up yet either.

There is less engine smell in the passenger compartment and either I am loosing my mind or I am hearing less engine noise - would bypass gases carry any sound with them when blowing out through the breather???

I drove the car into work this a.m. and will try to get some highway miles on her at lunch time, but it seems to be working.

Will advise after lunchtime drive... thanks again!

Dan

HSSS427 · #15 (**permalink**) 07-28-2006, 01:19 PM

So here's a pic of my setup: goose neck breather in the rear, and billet cap in the valve cover with a pcv valve inside it and hose running into vacum port in the base plate of the carb.

I'm read somewhere that having a breather and PCV negates the PCV effect as the breather doesn't allow enough pressure to let the PCV work. Is that true?

Also, getting oil blowing out the goose neck breather. Is that from not having enough "venting" going on, too much crankcase pressure, or just life with a 427 FE? I can certainly see why the originals had an oil recovery tank coming off the back.

I also have the option of running the PCV off the rear plate and either putting a breather cap on the valve cover or just closing that off. Any suggestions?

Sorry to hi-jack your thread Dan....