Aidan's loose oily bunghole actually runs a track lap
#9726
SADFab Destructive Testing Engineer
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Managed to toast another lifter. One of the cam lobes has some marking on it that I believe did this. Not sure if I overlooked it or whatever. Getting another lifter ordered.
**** this ****.
#9727
OEM it's primarily there to keep the spring from wearing direction on the aluminum. With the Supertech springs, you're supposed to keep it, although now it's just a .005" spacer, because instead of the spring going on top you have this:
That's the ST spring seat. On top of that go the springs:
That's a set of the heavy doubles. On top of those go the top mount (not sure what that's called), and the two keepers go inside that. The valve stem sticks up through the hole in the center, and the grooves on the stem engage with ridges in the keepers to lock it all together.
The .005" shim doesn't sound like much, but it's adding preload to the spring. Preload is important -- I measured my exhaust manifold pressure at 350 kpa at one point. That's 50 psi pressing on the top of the exhaust valve, and since the valve has an area of a bit more than a square inch, it means that there's 50+ pounds of force trying to shove the valve open during the intake stroke. So you need a bunch of preload to keep the valve up against the seat.
--Ian
(ack, stupid web site coughed up a hairball when I was editing this to add the bit about preload)
#9729
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PM me. My guest room is occupied next week, but the couch is available. Or if you just want a place to park where you can walk to the lakes without worrying about it. I actually need to go to SF soon anyway, so I can visit you there if you want.