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On 25 Apr 2005 at 18:22, Toby Erkson wrote: > True for a stock engine but hi-perf engines don't always follow the > rules. What has constantly been told to me is that a bigger engine > produces more case pressure (due to blow-by? I dunno) and thus the > valve cover vents actually move air out and towards the breather. I'm sure that normal blowby increases proportional to piston radius, but I wouldn't be surprised if most of what we hear comes from hi-perf jobs that are poorly done with poor quality parts and consequently suffer from extreme amounts of blowby. I'm sure that VW designed some head room into the system but there's no doubt a point where the 72-3 PCV system can be overwhelmed. I don't know where that point is, either, nor can I think of a simple way to measure it. It's possible that most of our 33 year old engines with this feature are already so worn that they don't work right, but mine SEEM to be fine. -- ******************************* Jim Adney, jadney@vwtype3.org Madison, Wisconsin, USA ******************************* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ List info at http://www.vwtype3.org/list | mailto:gregm@vwtype3.org ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~