Revisiting the breather hose air / oil separator design

September 13, 2011

Separating the oil from the air in the breather hose

some oil collected in the separator
Some oil collected in the air oil separator

I did a nifty upgrade to the breather hose and intake in August by putting an air/oil separator between the valve cover breather hose and the air intake. This was supposed to accumulate all the blow-by oil instead of sucking the oil back down into the intake manifold.

How did this work out? A Catalina trip and 32 engine hours later, I checked it out and found the air/oil separator had some oil in it. Great! That is what it was supposed to do.

some oil on the air intake
A drop of oil on the air intake

But there was also a dab of oil on the intake silencer.

oil collected on the foam filter
Oil collected on the foam filter

And there was oil collected on the foam filter inside the air intake silencer.

This was a bit disappointing, I expected ALL the oil to collect in the separator.

On the positive side:
  • the engine isn't starved for oxygen
  • the foam filter is easy enough to clean with regular dish detergent
  • the excess oil from the breather hose tied to the air intake is being sucked into the intake and not covering the engine

Now I just need a design tweek on the air/oil separator side...

Photos of this project

Breather hose to air intake photos

Related topic: Let the engine breathe - breather hose to air intake redesign


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