My aircooled Norton motorcycle is at 11:1, aluminum head & cast iron cylinder,
serious knocking on street gas unless octane boosted to around 100 via Klotz
octane boost. After the blending, gas runs about $5.00 a gallon, but I get 60
miles out of a gallon.
BTW: Summer in FLA doesn't provide much air cooling affect!
MWood24020@aol.com wrote:
> In a message dated 1/20/00 4:19:40 PM Pacific Standard Time, TSMIT@isotel.com
> writes:
>
> << So there's a topic worthy of discussion: Assuming we're using a mildly
> zoomy
> cam (let's say the Ford Motorsport E303 or equivalent), what's the maximum
> compression ratio we can run if we're going to use street gas (91 octane).
> Assume the engine will use 38 degrees max timing advance.
>
> Which heads are more susceptible to detonation?
>
> Comments? >>
>
> Common rule of thumb that I've heard from those that "know" (mostly by their
> mistakes) is 9.5 to 1 with iron heads, 10.5 to 1 with aluminum heads. Sounds
> a little high to me, but I guess that's what thicker head gaskets are good
> for...
> Mike
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