The Stovebolt Site Forums The Shop Area Engine Shop Oil catch can volume

I removed my road draft tube on my 235 and installed a PCV valve a few months ago. I decided to install an oil catch can just to see how much oil was going toward the intake. Did some common driving around town and some interstate driving to rack up a few miles. I noticed when I hit the gas there would be a quick fog inside the glass catch can ( Jar ) and then it would be gone. With an empty jar after driving 317 miles I accumulated 7 ounces of oil inside the catch can that did not make it inside the intake.I could never measure what was lost thru the road draft tube but that seem like a lot of oil? 1955 235 recently rebuilt and does not smoke. Good tight engine runs very well with no problems. Has anyone else with a PCV system noticed the same?

I had this same problem years ago with a 250 with an aftermarket valve cover. It came with no baffle around the vent hole and I was getting liquids in the pcv hose. I built a a round baffle packed with sst mesh and located it inside the hole in the valve cover.

I did the same thing inside the jar with stainless steel mesh. It works well to defuse the oil mist before it gets inside the intake. Did you ever measure your mileage with the amount of oil accumulated?

It is important to cover all of the bases when designing a custom PCV system, especially when drawing vacuum from the draft tube (virtually directly from the crankcase).
More modern PCV systems do not pull directly from the crankcase. They pull from the valve cover. There is a lot of oil splashing around in the crankcase making it a less-than-ideal place from which to draw vacuum.
Another factor to consider is what size orifice to use to prevent too much applied vacuum.
Another factor is to determine when is the ideal time to do the majority of the purging of crankcase contaminants. Modern PCV systems take this into account.
I don't have a PCV system on my Stovebolt engine. I religiously change my oil every 3,000 miles.
Carl