Re: Hollow stem valves
Somebody asked me to post some data, so here is a graph that contains a comparison of high and low pressure springs - 1238X (blue) is the lower of the two.
You can plainly see the higher pressure spring arrangement is not as stable as the lower pressure spring.......Key in on the nose deflections and bounce at closing. The latter is a mode that tends to break parts. In this case the higher pressure spring is bouncing .010" where the lower spring is about .002"-.003"
Also, a trace with a light-weight hollow stem valve (green) is included in the graph. In this case the lighter valve wasn't different enough to matter, but nobody should ever assume this is always the case. I've seen the same valve comparison with a different cam knock over 1,000 RPM of peak limiting speed out of a system when the heavier valve was installed.
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