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vlad01 wrote: ↑Sun Jan 21, 2024 9:46 pm Sounds really good. Regarding what Immortality said about draining the rocker cover.

A really counter intuitive thing about the rocker cover and ventilation and oil drainage is, they don't play nice together. An very renown Porsche and VW engine developer (when I had an interest in those things back when I was young ) told me a very valuable thing that I'll never forget, push rod engines and rocker breathers make things worse and that a good breather should be out of the crank case or in a V engine at least the valley if oil drainage is far easier than any blow by countering it.


So it goes like this, if your pushrod engine relies on oil drainage via small passages which they typically do and often these same passages are also for breathing in the OEM design. When a hot or race engine build is considered, then the blow by being vented up from the crank case and out the rocker is more forceful than the gravity draining the oil out of the head passages. So you get a situation when the oil is being essentially aerated back up the drains and the oil continues to accumulate, more so if the engine is turning some decent rpm which pumps more oil up there than normal. So all these things just exacerbate each other.

When you have a closed off rocker and head ventilation, then the pressure difference from the crank case and heads become similar or same. The oil can then assume it's normal draining. Any overflow issue is now going to be about the supply vs the draining, and no longer an air pressure forcing the drainage to back up and in worse cases in the reverse direction.


The best place from the top of my head (no pun) on this engine might be the dizzy hole, you might need to make or install some sort of air/oil separator to stop excessive oil mist venting out being where the crank is before it goes to the catch can, but it should be heaps better than the oil being forced to fill the rocker cover.

You should be able to confirm this but popping off the rocker oil cap after a pull like that and see how much oil has accumulated.

But the whole rocker cover and oil cap need to be air tight.

One of the ideas I have on my next hot engine which will require decent ventilation and a catch can or two plumbed back into the intake duct, I found a nice big spot under the throttle body in the intake valley for a breather than can be drilled and tapped or welded in, and with no balance shaft there should be ample opening for air to flow up and out without affecting drainage too much. I have seen lots of people drill the shit out of the valley all along the cam tunnel for "cam lubrication" and drainage but it often can initiate the block to crack straight down the valley.

vlad01 wrote: ↑Mon Jan 22, 2024 9:30 pm There certainly are pushrods with restrictors. I was also under the impression good solid and solid roller lifters for racing applications were already oil metered for less top end oil, no?