How do I calculate cubic inches

I am building a flathead and am trying to figure out different cubic inch setups like : 4.375 stroke and 4.125 bore with a 7 rod length and 2.00 rod pin any help? I prolly know how I just forgot anyhelp?

 

3.1416 x bore squared/4 x stroke x number of cylinders

 

0.7853982 X Bore(twice) X Stroke X # of cylinders. Your rods do not not mean a thing.

 

Thank you much guys what a great site

 

I keep getting crazy numbers any more help

 

Lots of FREE engine displacement calculators online.

All you have to do is search.

 

4.125 bore is not even remotely doable.

 

I don't want to start a ******* contest, but cubic inches equals one half bore size times one half bore size times Pi. "Pie are square" X stroke X number of cylenders.

3.14159X(bore+bore) would have the typical flathead over 600 cubes.

 

yeah you guys are right now that I am thihnking about it the bore is actually 3.3125 sorry wrong numbers

 

Never mind ......

 

Hear is a very cool site ,well worth a bookmark OnlineConversion.com From hat size to cooking and metal hardness ect,ck it out.............YG

 

468 Sould be your answer. Mutiple your your bore to its self for your bore #. Example 4.125 X 4.125 = 17.015625, thats your new bore #

 

sorry i gave you the wrong numbers bore 3.375 stroke 4.375

 

0.7853982 x (3.375 x 3.375) x 4.375 x 8

 

Wrong!! With this "formula" a 3.50 bore with a 3.50 stroke V-8 would be pumping 615.75 cubic inches.

The correct answer is 3.14159X1.75X1.75X3.5X8=269.39 cubic inches.

 

BORE X BORE X STROKE X .7854 X the number of cylinders. Nothing more, nothing less.

 

I'm not useing 3.14159, I used 0.7853982. More than one way to do this.

 

3.141592654 X 2.84765625 (Radius of 3.375 squared) X 4.375 (stroke) X 8 (number of cylinders) = 313.1161584 C.I.

 

Here is a link that will show you a picture. Be sure to multiply the results by the number of cylinders.

http://www.mathsteacher.com.au/year9/ch14_measurement/18_cylinder/cylinder.htm


Phil1934 has the right solution.

 

this is correct!!!!!!

 

Agreed, but when ya change the constant let a feller know.
Hell it took me 25 years to learn 3.14159, I ain't changing now.

 

I got 313.11616 so we are on the same page.

 

The volume of a cylinder is the area of the diameter times the stroke. To determine the area you square the radius (one half of the diameter) and multiply that by Pi (3.1416). Multiply this figure by the stroke to determine the volume of the cylinder. Multiply this by the number of cylinders to get the engine's displacement.

example: 4.2" bore X 3.8" stroke, 8 cylinders

Half of bore dia. is 2.1".
2.1" X 2.1" = 4.41"
4.41" X 3.1416 (Pi) = 13.85... square inches (area)
13.85" X 3.8" (bore) = 52.63 cubic inches (volume) per cylinder
52.63 cubic inches X 8 cylinders = 421.04 cubic inch displacement.

 

Yea the result is usually within a couple of hundred thou.

 

Go back and read what I posted here before hand, its there

 

This is a great place to great answers, sometimes they are correct.

 

Its 3.1416 times the radius of the bore squared times the stroke times the number of cylinders. 3.1416 times 1.65625 squared= 8.6179 X4.375=37.703 cubic inches per cylinder x 8 =301.627 Cu In.

 

Round it off brother to 3.1416, gives enough accuracy for ANYTHING we do

 

Fore any given motor if it's the only one you got,bore to max. size and stroke to max.size,add as many carbs as can fit on top of supercharger=just right cubic inches!

 

Ok, now what does that come out to in Torque and Horsepower Fonzi ?