Boring out

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Mar 17, 2006
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#1
when you bore a cylinder out any number, say .040 over, does that translate directly into cc's? so if you would have a 250 and bore it out .40 over would it now be considered 290?? just wondering because i thought it was this way but I heard a guy saying that his 125 was .080 over making it a 144.
 
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Feb 10, 2007
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#2
Nope...it has no direct correlation to displacement in cc's.

"40 over" describes how much bigger the piston is in diameter, that is .040 inches. The displacement in cc's is determined by the size of the bore multiplied by the length of the stroke.

A "40 over" 250 is probably about 251-252 cc's, I'm guessing.

Rotor
 
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#4
It will translate directly into ccs, but you need to know the bore you started with and the stroke. My elsinore is bored 1mm (0.040) over, so it is now 64.4 stroke x 71 mm bore, or 254.9 ccs. You can find all sorts of displacement calculators doing a google search.