Cubic inch question
 

I have a Ford 8ba that has been bored .040 over and has a Merc. crank. What cubic inch does this come out to? Thank you and sorry for my ignorance.

Re: Cubic inch question
 

261.8 (let's call it a 262).

Re: Cubic inch question
 

That tubman sure knows how to punch a calculator....on the money! DD

Re: Cubic inch question
 

Yeah, but I didn't have to look up the mathematical formula required. When I was in college taking physics, calculating devices (slide rules in my day) were OK during tests. They were checking your knowledge of Physics, not your math abilities.:rolleyes:

Re: Cubic inch question
 

I've known that formula (by heart) since junior high. And I do it the ".7854" way. DD

Re: Cubic inch question
 

Okay, I'm game. What does that fraction represent. Never did that well in physics. Terry

Re: Cubic inch question
 

So is my .080 over gonna be 269?

Re: Cubic inch question
 

268.33


(pi X bore radius squared x stroke x 8)

Re: Cubic inch question
 

Thanks cad, guess I better say 268.

Re: Cubic inch question
 

Thanks, that's what I came up with but was told it was wrong.

Re: Cubic inch question
 

Hey Terry....

OK, "0.7854" is a function of pi, accurate to at least four decimal places.

0.7854 = 3.1416/4 or (3.1416 divided by 4).

Example: Bore X Bore X Stroke X .7854 X 8 (cyls.) = Cu. In.

Your FIRST Example:

Bore = 3.1875 + 0.040 = 3.2275

Stroke = 4.0

Constant = .7854

Number of Cylinders = 8
__________________________________

So: 3.2275 X 3.2275 X 4 X 0.7854 X 8 = 261.80224

Re: Cubic inch question
 

I do it slightly different.

I punch in the bore (3.2275), then I hit the squared button (² ), after that, I multiple by .7854, then times stroke (4) and finally, times 8 = 261.80225148

Darn, I got a different answer, what happened ;)

One of the nice things about using .7854, is that on number pads, it is the top, left hand corner keys. Makes it a little easier for me.

Re: Cubic inch question
 

It would take me 10 years to understand why you square the bore measurement.

Re: Cubic inch question
 

You square it because you want the area of the cylinder.

Area of a circle is Pi r squared.

Because we know the bore rather than the radius, we have to use the alternative formula that uses the diameter.

Area of a circle is pi d squared all over 4. (over = divided by)

Volume of one cylinder of a stock 239 for example is:

3.1875 * 3.1875 * 3.1416 / 4 Which equals 7.9798. Unit is square inches.

Volume of a cylinder = area * length.

So 7.9798 * 3.75 = 29.9242. Now the unit is cubic inches. So just shy of 30 cu in.

Volume of the engine is volume of one cylinder times the number of cylinders.

So 29.9242 * 8 = 239.3936

Rounded to 239 for ease of reference.

I used a known engine because we are already familiar with the answer.

In the examples above the shortcut is to use pi/4. 3.1416/4 = .7854.

The above formulae are completely universal and by using centimeters the volume in cc can be calculated.

Mart.

Re: Cubic inch question
 

thanks, fellas. Terry

Re: Cubic inch question
 

In my dotage now, my sliderule days are long forgotten, but you can do more today with a $6.99 drugstore calculator than the best sliderule ever made.
My old sliderule was never much good for making straight lines anyway, with that bumpy thingy right there in the middle.
I will say though, I had a round one once that helped me earn free pizza in my sports car rally days. (Back in the day, you'd have to tell them if you didn't want anchovies.)
Come to think of it, I guess I could have used my sliderule to determine how much beer was in a "'Yard of Beer' Stein".

Re: Cubic inch question
 

Mart,


With respect, if we know the bore diameter, we automatically know the radius as it is one half of the diameter.

Re: Cubic inch question
 

Who says one only remembers 5 minutes of what they learned in 5 years of college?

You guys have proved them wrong��

Re: Cubic inch question
 

Aw, I retain very fond memories of a few 5 minute sessions in college! :D

Re: Cubic inch question
 

Determining the area of a circle is taught about grade 6 or 7. :D:D