Hot Rod Forum : Hotrodders Bulletin Board - View Single Post - measure valve lift at retainer
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Old 05-25-2008, 07:08 PM
Stroke Stroke is offline
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There is more to this along with what has been stated already. IMO, subtle changes in VT geometry will cause the things you are seeing here. Not always will max lift occur when the pattern is centered, nor will a centered pattern be the absolute correct geometry. Flex in the valvetrain components along with tolerance stacking play into this deal, as well as parts used. Checking springs do not load the components as do actual springs and their pressures and will net a different number, most always. I have tons of data in regards to this matter, and have sought to compile data for different rocker mfrs, as well as map (graph) lift at the retainer in 5* increments for 720* crank rotation for each, with up to three different pushrod lengths as well as varying valve lengths . They all net different results and give much to look at. On the geometry end of it, things are not as simple as most believe, and the only way to see these things is to actually check. Seeing is believing (read - actual measurements). My PC suffered a major meltdown though, and all the data from my notes etc. are still in that PC. I could redo all of the noted material, but that took a looong time to enter and all of that, and I've not had the chance to recover the entered data from the toasted PC, but I'll get to it - looks like in my extra spare time. This topic is a good source for debate and is much like the 'more than one way to skin a cat' deal. That being said, you may never see the advertised lift for your app, and if you do, I'd hazard a guess your geometry is wabi sabi, or, imperfect, impermanent, and incomplete. JMO
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