I purchased a set of roller rockers, standard ratio, and installed
them on my race engine. I subsequently removed them and gave them away.
Let me say up front that I screwed up installing them. Since my
standard rockers contacted the valve stem properly, I did not give
enough care to checking them.
I seized some valves in some guides, trashing an engine. Subsequently
I found that my trusted machine shop had not given me enough
clearance on my bronze guides, but during the rebuild I discovered
that the roller contact patch was not centered up on the valve stem,
so then rightly or wrongly I blamed some of the valve guide sticking
problem on the roller rockers too.
During this whole process I read everything I could lay my hands on
regarding roller rockers. What I learned was that centering them up
is sometimes a snap and sometimes nearly impossible. In the final
analysis on my engine, the valve stem protrusion above the head was
greater than stock (trying to use up that head) and there was nothing
I could do to center up the contact patch. And no, shimming up the
stands doesn't correct it. When I installed them on another head with
different valve stem protrusion, the geometry was okay.
If you'd like to read some really interesting stuff on this, take a look at
http://www.mid-lift.com/MASTER-INDEX.htm and look at the links
referring to mid-lift.
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