What does bored .30 or .60 over mean? - Ford Truck Enthusiasts Forums



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What does bored .30 or .60 over mean?

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Old 03-12-2004, 11:43 AM
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What does bored .30 or .60 over mean?

Never have quite understood that...I'm assuming it means that each cylinder has been bored .30 inches greater in diameter...
or .30 centimeters?
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Old 03-12-2004, 12:11 PM
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It means that the cylindar has been bored 0.030 or 0.060 over size in inches. If you look at a foreign car the over size measurements are in mm and are smaller.
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Old 03-12-2004, 12:13 PM
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Talisker,

So how would I compute the total new displacement if I had, say, a 460 that was bored over .060?

J
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Old 03-12-2004, 12:17 PM
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Take the actual ID, calculate the area of that diameter, and multiply by the actual stroke, multiply that by 8 all in the same units.
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Old 03-12-2004, 12:23 PM
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OK, so I'm adding .060 inches to whatever the diameter is?
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Old 03-12-2004, 12:38 PM
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Yup.

The volume for a cylinder formula is V=pi*D*D*H/4 , multiply by 8 for a V8 engine.

D is the cylinder bore diameter
H is the stroke (height of the cylinder)
pi=3.14159 (close enough)


hope that makes sense. It's not exactly easy to write forumlas on a PC.
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Old 03-12-2004, 02:15 PM
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It is always better to actually check the bore rather than assume that it is the "book" value + the overbore. On the other hand the book value + the over bore can't be too far off.

I am glad that there is someone else that only remembers pi to 3.14159.(good enogh for govenment work)
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Old 03-12-2004, 03:02 PM
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r 2 h .........

is the correct formula...or...3.14 x R x R x H....Radius..not diameter...right?
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Old 03-12-2004, 03:23 PM
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radius is half the diameter...

d/2, hence the 4 in the denominator.
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Old 03-12-2004, 03:27 PM
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gotcha....
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Old 03-15-2004, 09:38 AM
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I do <b>Bore x Bore x Stroke x .7854 x # of cylinders</b>. The .7854 is Pi divided by 4 (or thereabouts).
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Old 03-15-2004, 01:46 PM
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wanna get real fancy? (or really, really lazy)

a 460 starts with 4.32" bore, and 3.85" stroke.

http://raceabilene.com/kelly/hotrod/compression.html

Last edited by Mattsbox99; 03-15-2004 at 01:49 PM.
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Old 03-16-2004, 03:51 PM
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GO: Pi (bore)Radius, Squared Height(stroke)
3.14159 X (2.180x2.180) X 3.850 = 57.4808554166 X 8cyl. =459.85cu in
------------------------------------------------------------------------------------ add .060" bore(4.420") makes the radius 2.210" squared =4.8841x3.14159x3.85=59.07378x8cyl=472.6 cu inches
------------------------------------------------------------------------------------
472.60
-459.85
-----------
12.75 cubic inch increase in displacement
This would make this big block a real contender in any circle!
Huffer
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Old 03-16-2004, 05:20 PM
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If you don't want to mess with pi, but still want accuracy (eg if you have a calulator that doesn't have pi), just use 22/7.
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