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I understand that heat expands air and therefore the friction in the crankcase you will have pressure in the crankcase area that now needs to be relieved.. So what causes excessive crank case pressure? ie Windage tray? Aluminum heads? What? Do all engines RB, B, etc. create the same amount of pressure regardless of build? Thanks.

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Being that rings have a gap in them and the lack of 100%
sealing on the walls you have blow by, this is due
to the pressure in the cylinder and that pressure
slipping past the rings. All engines do not see the
same blow by, if its a "better build" it will have
less

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the movement of the crankshaft and oil flying off the rotating crankshaft and blowby all add up to crankcase pressure. A crankshaft scraper and a windage tray can help reduce and control the windage caused by the flying oil 15 to 45 hp increase on some motors during controlled dyno testing, depends on the RPM , windage and oil scraping. As already said the up and down movement of the pistons add to it also so the higher the RPM the more pumping and more pressurei if not relieved by breathers or a vacume source relieving the pressures. Longer stroke motors seem to make more pressures also due to the larger radius of the rotating parts