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Old 11-08-2013, 05:34 PM
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Finding cubic inches

Ok guys I've asked the question on how to know the cubic inches of an engine once it's been bored . I have a 502 Chevy bigblock ( of course) just had it punched .90 has stock stroke and crank can someone give me the formula for the true cubic inch of this engine ?
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Old 11-08-2013, 05:47 PM
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Just did this on another site...

There are many "witch doctor" formulas out there. There is one correct one.

Pi x R(2) x H x no. of cylinders (high school geometry, volume of a cylinder)

Pi = 3.14159 (close enough for our purposes)
R = bore x .5
H = stroke

Jim
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Old 11-08-2013, 05:48 PM
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Simple Google search, there are tons of calculators available. Here's one:

Calculate Cubic Inch Displacement

If you started out with a 4.466", 4" stroke (502 c.i.) and bored it to 4.556" you have a 522 c.i. motor (521.68).

Whether you can safely take a 502 block to .090 I have no idea, I assume you can.
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Old 11-08-2013, 06:05 PM
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(.7854) x 4.556 x 4.556 x 4 x 8 = 521.68 cubic inches.
The .7854 is one/fourth of pi and eliminates messin' with squaring the radius of the bore.

Mr. Peabody, this is hilarious....
"There are many "witch doctor" formulas out there. There is one correct one."
You need to get out more.
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Old 11-08-2013, 08:00 PM
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A simple "Witch Doctor" formula for CID of a 8 cylinder engine.

Bore x Bore X stroke X 3.1416 (Pi) X 2 ='s CID
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Old 11-08-2013, 08:00 PM
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I use Tech's formula,its the easiest,and you can change random bore numbers or stroke numbers to see different combos net
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Old 11-09-2013, 09:09 AM
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3.14 = pi is plenty close enough. Easiest is to use online calculator- plug in the numbers and hit enter. But that dont exercise your brain pan like doing it long hand tho. Wallace racing has a ton of calculators including one for cid- http://www.wallaceracing.com/cid.php
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Old 11-11-2013, 05:04 PM
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Sorry dude. Spent too much time in school, I guess. It's always best to stick to what is known to all and "works". The formula you use may work, but is much harder to remember. We were all taught Pi xR(2) x H. That's the geometric formula for the volume of a cylinder. Nothing more. Why muddy the water with abstract?

PAX

Jim
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Old 11-12-2013, 12:30 AM
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Memory can be funny some cannt remember the firing order of a chevy and might not have learned the formula of a cyl either. But if someione remembers a different formula for cid than using the volume of a cylinder, nothing I see wrong with that. Its the answer being correct that matters.
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Old 11-12-2013, 06:11 AM
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standard firing order of small block chev is
1 8 4 3 6 5 7 2
1 8 7 3 6 5 4 2 is the second optional firing order used in sbc
many custom firing orders have been tried for various reasons
the ".7854" is the most common way of calculating displacement.
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Old 11-12-2013, 07:07 AM
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Want to talk witch doctor, the 4/7 swap for a street chevy is a good one.. Nowhere near as common as the smal;l fords 15426378 and 13726548 firing orders. Then theres the LS 18726543 but I think every body gets the point. Ican agree .7854 times bore squared times stroke times # of holes is a very common formula and saves a couple key strokes but I cant say it (or any) is the MOST common. Again if it gets myou the right answer is what matters.
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Old 11-12-2013, 09:19 AM
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((the ".7854" is the most common way of calculating displacement.))

Did you know that is 1/4 slice of pie ?
3.1414/4= 0.78535. Then rounded because of the 5 ?
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Old 11-12-2013, 02:04 PM
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Quote:
Originally Posted by 68NovaSS View Post
Simple Google search, there are tons of calculators available. Here's one:

Calculate Cubic Inch Displacement
This is also what I do! I always take the easy way out, and Google usually keeps my brain clear for what little I can remember at my age!
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Old 11-12-2013, 03:22 PM
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I've heard if your an old guy like me, you have to use your mind more, or you will forget things...
Every now and then, I recall something that I had forgot from before...
It does seem to help.
And keep trying to learn more things. Myself, it's computer stuff, like HTML, and scripts, and designing things. Including doing animations, photo fixing, and so on. Got to keep active fellows...
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Old 11-12-2013, 05:43 PM
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Quote:
Originally Posted by Denny View Post
I've heard if your an old guy like me, you have to use your mind more, or you will forget things...
Every now and then, I recall something that I had forgot from before...
It does seem to help.
And keep trying to learn more things. Myself, it's computer stuff, like HTML, and scripts, and designing things. Including doing animations, photo fixing, and so on. Got to keep active fellows...
Someone may have told me that, but I forgot to write it down if they did!
I can't afford to push any more important info out these days!
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