View Full Version : Calculating CID


rad454
Mar 12th, 09, 10:08 PM
Gentlemen,

My engine builder punched my 454 out .040 over. What CID doe's this make the engine? :confused:

Also, is there a generic formula for calculating this?

Mahalo in advance.

pdq67
Mar 12th, 09, 10:40 PM
Dam guy, get your old math book out and figure how big it is!

BUT I figure very close off the top of my head, a 462 or so??

pdq67

jkaufman
Mar 12th, 09, 11:07 PM
Gentlemen,

My engine builder punched my 454 out .040 over. What CID doe's this make the engine? :confused:

Also, is there a generic formula for calculating this?

Mahalo in advance.

Bore area * stroke * number of cylinders.

Bore area = pi (3.14) * (radius of bore)^2

For example, I have a 327. That's a 4" bore (2" radius) and 3.25" stroke.
Bore area = 3.14*(2)^2 = 12.56 sq. in.
Multiply that by the stroke = 12.56 sq. in. * 3.25 in. = 40.82 cu. in. per cylinder
Multiply by 8 = 326.56 or "327"

If I remember correctly, your 454 would have had a 4.25" bore and a 4" stroke.
3.14((2.125)^2) = 14.1790625 sq. in.
14.1690625(4) = 56.71625 cu. in./cylinder
56.71625(8) = 453.73 or "454"

So plug in your new bore and re-calculate:
3.14((2.145)^2) = 14.4472185 sq. in.
Answer(4) = 57.788874 cu. in./cylinder
Answer(8) = 462.310992

Good job pdq! :)

BPOS
Mar 13th, 09, 05:39 AM
An even easier way!!

(bore squared) X stroke X .7854 X number of cylinders = CID

rad454
Mar 13th, 09, 08:25 AM
Jkaufman,
When I asked my engine builder how to make more power and maintane streetability he simply said, (with a rather dull look on his face) "when in doubt, bore it out."
You and our Physicist would get along great. That is probably the most well thought out technical answer in the whole Team Camaro website.
Thx
rad454

Everett#2390
Mar 13th, 09, 09:32 AM
Kindda the only way to figure the volume.
Al's formula is a derivative of the original formula, I think.

jkaufman
Mar 13th, 09, 11:54 AM
True enough, Al. You can square the bore and take 1/4 of pi. That is indeed the same formula (actually a tiny bit more accurate, because it takes pi out to 4 decimal places instead of what I did: 2 decimal places). That's probably easier for everyone anyways, because then you don't have to divide your bore by 2 to get the radius. Just gotta remember the 0.7854 (pi/4). Thanks!

:) Glad you liked it, Louie!