Don---Unleaded fuel has been getting a bad rap for reasons unrelated to
containing no lead. The Tetra Ethyl (lead) that has been removed was
once a relatively cheap way to raise the octane. It also happened to
cushion the face of the valves and their seats. Fuel rated at a high
enough octane will ward off detonation with or without lead. This
detonation is what must be avoided, esp. with cast pistons, when
considering the cylinder pressure of an engine. As stated by Jim, many
things should be considered when raising the pressure.
Generally speaking, a 9.5:1 CR will not cause the stock, cast aluminum
pistons to melt, nor warp. However, detonation can break these at the
ring lands if you try to go much higher. Then you might have to resort
to gadgets, or retard ignition timing too much, (less power) or purchase
fuel with a higher rating than what you can get at the pump.
More bother than it's worth?!
Dick
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