new displacment after rebore
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08-14-2003, 09:12 AM
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08-14-2003, 10:19 AM
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#5
08-20-2003, 12:58 AM
new displacment after rebore
Chuky66
Here is a formula that I use.
0.785982 - X - Bore - X - Bore - X - Stroke - X - Number of Cylinders = CID
Don't ask me to explain it, I copied it from Hot Rod magizine years & years ago.
It is accurate though to the best of my knowledge.
400 Ford bored 0.30
0.785982 X 4.030 X 4.030 (=16.2409) X 4.00 X 8 = 408.17833 CID
Here is a formula that I use.0.785982 - X - Bore - X - Bore - X - Stroke - X - Number of Cylinders = CID
Don't ask me to explain it, I copied it from Hot Rod magizine years & years ago.
It is accurate though to the best of my knowledge.400 Ford bored 0.30
0.785982 X 4.030 X 4.030 (=16.2409) X 4.00 X 8 = 408.17833 CID
Last edited by Superdave; 08-20-2003 at 01:05 AM.
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09-04-2003, 12:02 PM
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new displacment after rebore
the formula for displacement isn't as complicated as you might think:
it's the volume of 1 cylinder x how many cylinders you have
the height of the cylinder is your stroke
the diameter of your cylinder is the bore
V=(pi, or 3.1415)*diameter^2*height/4
a 302 bored .030" over is as follows:
(3.1415)*(4.030"^2)*3.00"/4, then * 8 cylinders=306.134 in^3
a 302 bored .060" is as follows:
(3.1415)*(4.060"^2)*3.00"/4, then * 8 cylinders=310.709 in^3
it's the volume of 1 cylinder x how many cylinders you have
the height of the cylinder is your stroke
the diameter of your cylinder is the bore
V=(pi, or 3.1415)*diameter^2*height/4
a 302 bored .030" over is as follows:
(3.1415)*(4.030"^2)*3.00"/4, then * 8 cylinders=306.134 in^3
a 302 bored .060" is as follows:
(3.1415)*(4.060"^2)*3.00"/4, then * 8 cylinders=310.709 in^3
#14
09-04-2003, 01:31 PM
new displacment after rebore
TorqueKing
Well it looks like your formula came up a little different than the one I had copied from Hot-Rod magizine years and years ago. Is the formula I copied not an accurate way of doing this then.
I see its very close, but not the same. I had 310.9 and your's is 310.7.
Well it looks like your formula came up a little different than the one I had copied from Hot-Rod magizine years and years ago. Is the formula I copied not an accurate way of doing this then.
I see its very close, but not the same. I had 310.9 and your's is 310.7.
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09-04-2003, 01:53 PM
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new displacment after rebore
It's because I use the real Pi, they probably just used 3.14.
the real thing is the ultimate irrational number, but it starts out something like this:
3.1415926535898
whenever you see a formula in a magazine, they've probably rounded all the constants up, because it's easier to type into a calculator. I've got a machine here that could probably guide the space shuttle, a TI-89, at my desk.
In fact, the .78xxx that you multiply first is a conversion factor, which has been rounded up from the real value. These formulas start out like mine, then they take all the other numbers and factors and make them a single "magic" number that you multiply by to get the answer. Simplified formulas are never as accurate as the real thing, especially because you can't manipulate them. What if one of your Fast-and-the-bi-curious Honda friends gave you his bore and stroke in Centimeters? you can't use that formula in Hot Rod. Use the volume formula instead and it will give you the volume in cubic centimeters, or cc's. cc's just so happen to be related to Liters in that 1,000 cc's=1 Liter.
Obviously for what we're doing, the Hot Rod formula is fine. i don't think too many races have been won by a .2 in^3 difference in displacement. TK
the real thing is the ultimate irrational number, but it starts out something like this:
3.1415926535898
whenever you see a formula in a magazine, they've probably rounded all the constants up, because it's easier to type into a calculator. I've got a machine here that could probably guide the space shuttle, a TI-89, at my desk.
In fact, the .78xxx that you multiply first is a conversion factor, which has been rounded up from the real value. These formulas start out like mine, then they take all the other numbers and factors and make them a single "magic" number that you multiply by to get the answer. Simplified formulas are never as accurate as the real thing, especially because you can't manipulate them. What if one of your Fast-and-the-bi-curious Honda friends gave you his bore and stroke in Centimeters? you can't use that formula in Hot Rod. Use the volume formula instead and it will give you the volume in cubic centimeters, or cc's. cc's just so happen to be related to Liters in that 1,000 cc's=1 Liter.
Obviously for what we're doing, the Hot Rod formula is fine. i don't think too many races have been won by a .2 in^3 difference in displacement. TK