Figuring CCs

[88workcar]

How do you figure out the CCs of a engine. I tried to mutiply the stoke times the bore, that is way off. Let use 3 cyl X 80mm X 76MM for an example.

[joe ross]

If its 80mm bore X 75mm stroke = 1130.97 cc

[Roy Hodges]

How do you figure out the CCs of a engine. I tried to mutiply the stoke times the bore, that is way off. Let use 3 cyl X 80mm X 76MM for an example.

.................................................. .................................................. .................................................. .................................................. .............................................. The formula I use is ; radius X radius X 3.1416 X stroke X #of cylinders. ......................... Wanna know somethin' funny? here's a good one for an 8 cylinder engine, with a 4" bore, use the stroke X 100 ,then add 2inches that's the total cubes . example a 350 chevy : 4" bore and 3.48" stroke. =3.48 & 2=350 all this, I guess it's whats called "a co-incedence of numbers.

[mobil1]

With sort of oil.
Piston in tdc, fluid thru sparkplug hole and measure how much goes into it...

[JohnsonM50]

Bore x stroke is displacement not including the space left in the combustion chamber at TDC, measured in cc's.

[Steve Litzell]

How do you figure out the CCs of a engine. I tried to mutiply the stoke times the bore, that is way off. Let use 3 cyl X 80mm X 76MM for an example.

Bore x 2 x stroke x .7854 x number of cylinders. this works for inches and cc's. Just use metric measurement or inch measurement for the cubic inch or metric number.

[Mark75H]

The formula does not use bore, it uses radius, which is half of bore (the distance from the center of a circle to the outer edge, not the distance all the way across a circle).

Roy pointed out the correct formula. Quite often you hear "Pi R squared" spoken as the formula for a circle. Pi (the 16th letter in the Greek alphabet, π) is the mathematical constant representing the relationship of the circumference of a circle to its radius (the distance around the outside divided by the distance halfway across). That relationship just happens to be related to the area inside the circle, so it has to be used to find the area.

The Greek letter π was first adopted for the number as an abbreviation of the Greek word for perimeter (περίμετρος), or as an abbreviation for "periphery/diameter", by William Jones in 1706. The constant is also known as Archimedes' Constant, after Archimedes of Syracuse who provided an approximation of the number during the 3rd century BC, although this name is uncommon today.

http://en.wikipedia.org/wiki/Pi

But what we are looking for is the area of a cylinder (as a geometric shape). The formula for any geometric cylinder is the area of the circle formed by its top or bottom times its height. In our case, the height is the stroke, so just multiply the area of the bore by stroke. Since we want to know the total displacement volume of the motor, we then multiply by the number of cylinders.


Here's the way the its usually written:

π x R² x stroke x number of cylinders

So, half of bore multiplied by half of bore multiplied by 3.1416 multiplied by stroke multiplied by the number of cylinders (just like Roy said).


Jeff pointed out something different, and that is how to measure the cylinder head volume or "compression clearance" of a cylinder head (which in boat racing, is almost always expressed in metric cc's (cubic centimeters) even if we talk about the rest of the motor in cubic inches. You measure that with a tool called a burette that looks like this


You can use a smaller tool like a little calibrated eye dropper but it will take much longer and not be as accurate.

Jason showed he was looking for displacement rather than clearance by starting us off with the number of cylinders and 2 numbers very likely representing a bore and a stroke.

[88workcar]

Thanks fellas, yes I was after engine displacement. I do know how to and do cc heads on occasion.

[Steve Litzell]

Are you saying my formula is not correct???Bore X 2 is same as bore X bore. Both forulas are good. Roy's method is what I was taught many years ago when I had hair and was very young. My formula is also correct for both metric and American, and if you try it you will see that it is spot on. It is just more modern way that's all. Steve

[JohnsonM50]

I wrote "Bore x stroke is displacement" which is technically incorrect, bore area x stroke distance would be exact x [# of cyl's]