PF,
I have a pair of 10:1 Keith Black hypereutetic pistons in my '96 FLHR Harley-Davidson. They are set up to run at about 0.005 piston to wall clearance, and therefore, are very quiet, much more so than a forged piston. One thing I noticed in using these pistons is you can dial back the advance by 2-4 degrees without loosing any power. This made my motor less prone to detonation on unleaded gas.
I'm not a metalurgist, but I read that the pistons are made from a T-6 aluminium alloy, then treated to a molten salt bath, a process which imparts some special qualities to the alloy.
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'81 SC Coupe (aka: "Blue Bomber")
Member: SCWDP
Canada West Region PCA
The Blue Bomber's Website
"If it ain't broke...we'll help you fix it 'til it is!"
[This message has been edited by Doug Zielke (edited 10-24-2001).]