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Math formula for displacement increase after bore

Old Nov 8, 2001 | 08:50 PM
  #1  
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Math formula for displacement increase after bore

Guys if i have a 350 bored at .60 it isnt a 350 anymore am i right ?
what is the formula to calculate my displacement after i bored the engine ?
Thanks
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Old Nov 8, 2001 | 09:04 PM
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On a normal 350 the bore is 4.000" and the stroke is 3.48". To convert the bore diameter to radius, divide by 2. The volume of each cylinder is stroke*3.14*(bore/2)^2.
So 3.48*3.14*(4.000/2)^2=43.73 Then multiply by 8 for all 8 cylinders. It makes about 349.8.
So for a 350 bored .060 over, the diameter changes to 4.060.
8*3.48*3.14*(4.060/2)^2=360.4
You got a 360 now.

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Old Nov 8, 2001 | 09:20 PM
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now that your question is answered, i have one, y did u bore your block .60 over. a stadard block doesnt have thick enough walls to do this. at high RPM your piston will be pretty unstable

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Old Nov 8, 2001 | 09:37 PM
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<font face="Verdana, Arial" size="2">Originally posted by sammycalderon:
Guys if i have a 350 bored at .60 it isnt a 350 anymore am i right ?
what is the formula to calculate my displacement after i bored the engine ?
Thanks
</font>
If you have MS Excel or Quattro Pro, this sheet has all the calculations you're asking for:

Engine Calculations

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Later,
Vader
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If you want to beat the World, it might reach up and pull you down...
Adobe Acrobat Reader
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Old Nov 8, 2001 | 11:15 PM
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Vicious... thats one hacked formula... interesting nonetheless. Another way to look at it is:

bore diameter ^2 * length of stroke * number of cylinders * .7854 (constant) = CI

make the measurements in centimeters and you come out with CC's...

Hey, to each his own.
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Old Nov 9, 2001 | 12:09 AM
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My Visor doesn't have 0.78539816339745 loaded in it (Pi divided by 4), but it does have 3.1415926535898 "constantly" at my disposal...

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Old Nov 9, 2001 | 09:17 AM
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I hope you mean that it's bored 0.060" and not 0.600"!If it's really been bored .60 then you can probably see daylight through the cylinder wall, if you're not already into the water jacket.
-Rich-
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Old Nov 9, 2001 | 11:26 AM
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Xenodrgn, I basically pulled that equation out my butt using common sense (mathematical genius that I am, yeah, right). But my reasoning here was that the area of a circle is pi*r^2. So that's why I divided the diameter by 2 and multiplied by pi. Instead you multiplied the diameter by .7854 which is the same as 3.1416/4 or pi/(2^2). Just trying to explain myself here. Both equations work, but I must admit, yours looks much simpler.

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Old Nov 9, 2001 | 11:59 AM
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Actually, both ViciousZ and Xenodgrn's formulas are the same. As Vicious pointed out, Pi*R^2 = D^2*Pi/4. The Constant given by Xenodgrn is just Pi/4 to compensate for use D^2 instead of R^2, as pointed out by ViciousZ.

I should point out the Pi*R^2 is the more "commonly" used formula for calculating Area rather than D^2*Pi/4. You both pass the math test.

[This message has been edited by Glenn91L98GTA (edited November 09, 2001).]
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Old Nov 9, 2001 | 05:09 PM
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The easiest formula I've found is in the back of my PAW catalog.

bore * bore * stroke * .7854 = "X"

"X" * no. of cylinders = total displacement.



That's the formula us folk 'round here use.

AJ
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