I used to have a math equation were you could enter stroke X piston diameter X something else? You could come up with your cc`s after you bore it out. Does anyone know it. I seen it some where on the net before.

 

Same equation just have to adjust the numbers for the bore (and stroke if changed.) Displacement in cc's is :
[(bore in cm's)/2 X (bore in cm's)/2 X 22/7] X stroke in cm's.

 

Jason 454

This will also give you your engine displacement in cc's

(bore in mm's) x (bore in mm's) x (stroke in mm's) x 3.14
__________________________________________________ _______
4000




Doug

 

I have a quadracer lt500 engine. It is bored to 88mm, the stroke is 86mm, if I take these in 88x88x86x3.14 it equals 2091189.7cc`s? I know it doesnt have that many cc`s at .080 over? What am I doing wrong.

 

Jason:

Using the formula which I gave you the answer would be as follows:

44mm = 4.4 cm (1/2 bore expressed in cm)
86mm = 8.6 cm (stroke in cm)
Pi = 22/7 or 3.14286

calculation reads [4.4 X 4.4 X 8.6 X 22] / 7 = 523.273 cm sq.


Using the formula provided by "Doug" there is a slight difference because he rounded the Pi constant to 3.14

His calculation would be as follows:

[88 X 88 X 86 X 3.14] / 4000 (dividing by 4000 is what you forgot)= 522.797 cc sq. (close enough)

For either calculation the rounded displacement becomes 523 cc sq.

 

CC=Piston Diameter in inches*PIE(3.141592654)*Stroke
piston times pie times stroke
MM=Inches*25.4
Inches=mm\25.4

 

I use (bore)x(bore)x(stroke)x(.0007854)

 

I use like Dill


(Bore in MM)x(Bore in MM)x(Stroke in MM)x(.0007854) = CC





or (Bore in MM x Bore in MM x Stroke in MM)x 0.7854/1000 = CC

 

Thanks everyone. That last equation was the one I once had. I wont loose it this time.

 

If you are reading the numbers out of the Weisco book you can do the math that way. But out in the field when I tear an engine down at a race very few people have a set of guages that read in mm. What they have is one that reads in inches, so what I use to find the cc of the engines when I check a engine is:

V=(pi)*r*r*h*16.387

this is when you measure the bore and stroke in inches. The formula that dill gave was if again the numbers were in inches. If you munbers are in cm just use the following formula. To go from mm to cm just move the decimal point one place to the left to get cm.

V=(pi)r*r*h