A Slippery Situation, or Smoke and Mirrors

"MM54" (mm54mk2) 05/09/2020 at 12:45 • Filed to: '71Chevelle

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I don’t know why, but I enjoy titling posts like novels from 1900. It’s slippery because it involves oil, and there was also smoke visible in the car’s mirrors!

When I took the Chevelle into its short term storage (for garage renovations) it was the first long drive it went on, and I noticed that it smoked at hot idle. Before bringing it back, I checked my primary suspicion and did indeed find oil inside the vacuum line to the PCV.

As a refresher, the PCV is more or less a metered vacuum leak which pulls fumes out of the engine (there is a breather on the other side to let in fresh air ) for an array of benefits, including making the oil last longer and decreasing crankcase condensation. I had installed mine on a neat adapter I found, which screws into the fill plug on the valve cover and thus serves double-duty.

Unfortunately, this placed it directly over a rocker arm, which means at high engine speeds there is literally a jet of oil onto the bottom of the adapter, which after a short while would fill with oil and lead to A Lot going through the PCV and into the intake .

The fill port has no provision to install a baffle (why would it) so this means I had to actually put it where you’re meant to, in the front of the valve cover (which I was able to install a baffle inside of to prevent oil from spraying into the PCV valve; sorry, no pictures).

A small length of 3/8" aluminum fuel line made for a nice turn from the PCV valve to the vacuum line

A bit of rerouting lines later, I don’t think it turned out too bad. Not as pretty as before, but at least it shouldn’t be ingesting vast quantities of oil in high-vacuum (idle & decel) scenarios.

As a fun fact to close things out, when I took the PCV and its hose off, there was several mL of oil that came runn ing out of the hose. It was sucking up a lot of oil.

functionoverfashion > MM54 05/09/2020 at 12:50

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Reminds me I’ve got to improve whatever system there is on my truck for this, which is not much. There’s visible condensation in the oil fill tube which is independent of the valve covers in this case. Those are totally sealed, except for the leaking gaskets. But my engine uses a lot of oil in a number of ways, as I’m reminded when I drive it every day like I am now. 

Just Jeepin' > MM54 05/09/2020 at 13:02

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I don’t know why, but I enjoy titling posts like novels from 1900. 

That’s easily one of my favorite parts about writing something for Oppo: trying to come up with a good title.

shop-teacher > MM54 05/09/2020 at 13:17

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Nicely done!

MM54 > functionoverfashion 05/09/2020 at 14:06

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I suspect you’ll find a draft tube from the rear of the intake area running down to nothing (as in open on the end) . The idea is it allows pressure out and at speed there would be some marginal venturi effect to pull out vapors, but it’s primarily just an open vent. I think there are companies that make parts to put a PCV valve in that line, which you’d then plumb back to intake vacuum. You’d then need some sort of breather, which could probably be accomplished with a breather on the oil fill cap.

MM54 > Just Jeepin' 05/09/2020 at 14:07

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That and when the opportunity for a clever tag presents itself

MM54 > shop-teacher 05/09/2020 at 14:08

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Thanks!

Just Jeepin' > MM54 05/09/2020 at 14:14

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I’ve been slow on that front. Need to up my game.

functionoverfashion > MM54 05/09/2020 at 22:25

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Yes, it does have a “road draft tube” which I’ve been told not to mess with unless I want to go down a rabbit hole. Like you said, it’s doable with some conversion parts, etc. but I guess for the short term - which in this truck is like, 5 years - I’ll focus on fixing obvious leaks first.