jtranger

I have the intake off my 327/365 and the heads are out to the machine shop. I had some oil burning and plug fouling. I noticed oil in the throat of the intake manifold. The carb is not original and is pulling full manifold vacuum from an inline pcv valve connected to the oil fill tube. The vacuum from the carb is pulling in air from the oil fill tube / crankcase.

Is this pcv set up right and could the vacuum from the carb be pulling oil into the manifold and cylinders? If this is inline pcv is not set up correct, what would be the best way to set it up with this carb? Attached are photo's. Thanks

66jack

My L79 has the hose hooked up the "plug" on top of intake at the back of carb..i can see the top of it in your pic...

jtranger

I believe that would be the same as my set up as it would be pulling full manifold vacuum into the intake from the oil fill tube instead of the carb vacuum, correct?

66jack

I might be wrong but I think it would pull MORE from where you have it hooked up in your pic...

Maybe you can re-plumb it at take a reading from the back, top, of intake...


I looked at your "pcv" hookup....is that brass inline a pcv?...if it is, is it directional?

jtranger

Yes it directional. Pulling in air from the oil fill tube fitting into carb full manifold vacuum.

wmf62

yes it can, pulled it into my FI plenum. that front tube doesn't have an oil separator like a valve cover or the 'tomato can' under the manifold.

Bill

TCracingCA

If you have to smog check it or maybe you want it concourse correct for a car show, then have the hose hooked up. My opinion remove the hose connection, plug the back port on the carb and vent the engine using the exhaust or naturally to the atmosphere using breathers if you are driving the car! I never want oil in my intake tract!!!!!!!!!!!

65tripleblack

Don't the '66-'67's have the pcv plumbed in the same way as jtranger? And the '64-'65 use the same routing except that .090" orifice is used instead of metered pcv?

65tripleblack

If the engine/plumbing/metering is AOK, would there still be oil in the plenum/runners?
Are all pcv's the same?

wmf62

i agree, but with all the oil flying around in the lifter valley, some of it is gonna get sucked up into the pcv. his pic didn't look like a lot, but then i don't know over what period of time it collected; and those ribs are a perfect place for it to collect and not swept away. pulling into the other manifold port would be a better idea as the runner will be smooth......
Bill

Frankie the Fink

The answer is "yes"....you can have oil 'pullover' using full manifold vacuum in a PCV setup. Full manifold vacuum is the same regardless of where you tap into it...16" of vacuum is the same at the carb or the intake (assuming the fittings are similarly sized).

First off, you need to make sure you are using the right PCV valve and that all oil baffles are in place. Even then some engines are just finicky - I had to put an oil separator in my PCV line to draw off the liquid oil from the vapor when I converted from road draft tube to an open PCV system. At each oil change I have about a teaspoon of oil in the separator that I dump out. You wouldn't even believe the smoke cloud that small amount of oil will make if it goes into the intake and is burned out the exhaust. Only happens on decel from high-RPMs but is embarrassing as all hell.

ssgnco

The way the PCV works, you are going to get some oil vapor somewhere in the intake. Older cars just vented the crankcase to the road. PCV ("positive") use vacuum to pull exhaust gasses leaking by the rings out of the crankcase. The only place you have vacuum is in the intake somewhere. The amount of oil you get depends on where the system draws on (oil fill tube, baffled valve cover, etc) and how much flow you have (controlled by amount of leakage and PCV valve/orifice). If you have a lot of oil, it could be because your rings are leaking more than you would like. The oil could just be an indicator of excessive exhaust leaking by the rings.

Did you do a leakdown test before you pulled the heads?

Cheers
Greg

wmf62

here's a solution to the 'oil flying around' problem, and also keeps hot oil off the bottom of the intake manifold...
Bill

ssgnco

Interesting. There are also some methods to increase flow out of the valley to reduce the amount of oil that hangs out up there.

65tripleblack

One can do the mods pointed out in posts #13 and #14 and still have oil in the intake ports. With a roller cam, one can install standpipes in the return holes over the camshaft and have all of the oil return down the front and rear holes. Original engines using oil separators? Puff of oil smoke on the decel only?

Installing a baffle in the oil fill tube will cure the problem???

wmf62

i think it would be possible to loosely place a stainless steel type of 'chore boy' pot scrubber in the fill tube, below the extraction point, to act as an oil separator and still allow oil to be added (albeit slowly... )
Bill

MikeM

I think a little oily looking substance laying in those ribs is probably somewhat normal. It may not be oil or totally oil, it may be the heavy stuff in gasoline that hasn't evaporated. I don't think it's anything to be concerned about unless you're losiing oil or the exhaust is smoking for no understandable reason.

One thing I'd look at which has already been mentioned is making sure you are uiing a PVC valve that is calibrated to your engine.

MikeM

After giving your picture a second look, that "PCV" valve doesn't look like one to me. May be but I'm sure you know what you have.

Also, since you appear to have the correct oil fill tube that allows the PCV valve to screw into the fill tube, you should be able to find/use the correct AC replacement for your engine.

65tripleblack

The crack smokers on this forum wouldn't appreciate that. Besides, choir boy is made of copper.

I'm not sure that's a good idea in case a piece becomes dislodged and you-know-what happens. Repeating: baffling that oil fill tube doesn't always help.

Frankie the Fink

[QUOTE=65tripleblack;1583181245]I'm not sure that's a good idea in case a piece becomes dislodged and you-know-what happens.
I considered that for my C1 oil separator but discarded the idea for this very reason... Prob unlikely but it only takes one time