Early 411LE with no PCV-valve, whats the downside?

[Lars S]

Im putting my '70 411LE engine together and can see that there is no PCV valve in the oil filler, no19 below (and also the heads have no vent tubes).
There is no air restriction at all in the hose connection at the oil filler.

The hose from the filler goes straight to the air cleaner and not to the plenum as on later models so I guess thats why the PCV valve could be skipped - the breathing of the case did not affect how much air that vent into the plenum.
Guess the downside was that there is no (or wery little) breathing at idle and when driving with small throttle opening - not much underpressure in the air cleaner.

Are there other reasons why they later went to a more complicated solution - not having the PCV to act as a vacuum leak must be a big adventage on a D-jet?

/Lars S

_________________
Porsche 914 -72, Bahia Red daily driver
VW411 2-d -70, White, sold
VW412 4-d, -73, Gold Metallic, daily driver
Suzuki T500, -69, Candy Gold, sold
Suzuki K50, -77, Black, daily driver
BMW R69S -69, White, sold
Husqvarna 118cc, -47, Black, Sold

[raygreenwood]

Happy New Year Lars!

There is a small to moderate benefit to the engine from the PCV valve having manifold vacuum.
Because it "PULLS" a little more air through the rocker boxes.....I have noticed that long with standard 3000 mile oil changes it helps keep the rocker boxes very clean.

I have also found anecdotal evidence that when using the PCV valve....without the flap and spring and just hoing to a constant 3-4mm orifice and retuning around that constant vacuum source.......it keeps a lot of the oil from building up in the valve cover at highway rpm....by helping to pull oil through the pushrod tubes when it build uo to any significant depth.

I figured this out when doing highway speed drives and pulling over quickly to pop the covers off to do hot valve lash checks. Less oil drippage.
It was moderately better with constant flow. It also believe using the factory windage tray helps this.

More to your question....yes....not having the PCV ported to the manifold makes tuning the D-Jet system less problemtic and more accurate. You also get less oil vapor into the MPS over time......and the case IS still vented so you do get the overall advantage of PCV.

The issues with D-jet tunimg and MPS tuning are a significant issue with the PCV ported to the manifold plenum. It tunes much better when the PCV is turned into a constant flow orifice. Ray

[Lars S]

Wery much thank you Ray and a Happy New Year!

/Lars S
_________________
Porsche 914 -72, Bahia Red daily driver
VW411 2-d -70, White, sold
VW412 4-d, -73, Gold Metallic, daily driver
Suzuki T500, -69, Candy Gold, sold
Suzuki K50, -77, Black, daily driver
BMW R69S -69, White, sold
Husqvarna 118cc, -47, Black, Sold