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cnavarro cnavarro is offline
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Join Date: Oct 2001
Location: Momence, IL 60954
Posts: 1,847
I'm not sure if i'm reading it wrong, but i'll clarify otherwise. Since this seems to be a hot topic, I did some research. Back when we made "biral" cylinders, we used spun cast ductile liners (trade material MOLY 2000) which they quote on La Sleeve's website as being 48,000-53,000 psi yield strength (lower than I was actually expecting). I don't claim to know what liners JB uses and for all we know, they are using something even better, which is possibly the case. Regardless, that means the average ductile iron liner that is commonly used is right on par with the alloy we use for our cylinders, strength wise. It's at operating temperature where there is a difference, being that the ductile iron liners do remain stronger at temp BUT if you exceed the thermal capacity, no amount of strength will keep the liner from going south.

That said, your only limitation is how much heat you generate and how long a cylinder can stay dimensionally stable at that level. Case in point- cast iron 103s on the Porsche 914 have a lifespan of 5-10k miles, even at less than 50 HP per cylinder. Although they are physically more dimensionally stable than one of our aluminum cylinders at the same bore, they still fail by means of going out of round and not sealing at the cylinder head. We've also observed that the heads get pounded from the expansion and contraction differences. And that's all normally aspirated.

You just have to find the point where longevity vs. performance vs. cost is justified.
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Charles Navarro
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Old 10-03-2005, 02:03 PM
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