i had my block decked 10 thousanths, and bored 40. i thought that would give me a 358 because its bored 40 over. then, i had a guy tell me that decking takes away from the cubic inch. if so, how can i tell how many cubic inches i have.

 

A 350 bored 0.040" is a 357, not 358. Decking doesnt take away the cubic inches, and 10 thousandths isnt enough to affect it that much either.

The volume of the cylinder is determined by the bore size and the distance the piston travels from bottom to top.

The formula is Pi x R2 x height.

Pi = 3.14159
R2 = radius squared = 2.02 x 2.02 = 4.0804
height = 3.48" (stock stroke)

3.14159 x 4.0804 x 3.48 = 44.61 cubic inches per cylinder

44.61 x 8 cylinders = 356.879 or rounded to 357 cubic inches.

 

Decking a block increases the compression ratio.

 

Not trying to push this off subject....
but I'm curious of something....
Why is there a decimal on a standard measurement?
That would indicate the incorporation of the metric system where it does not belong.
It's always made me wonder why America just doesn't adopt the superior metric system....haha. (I'm sure someone will try to shoot that down)
If you can count money...you can use metric. It is that simple.
Sorry for the brief hijack....but 3.48" just does not even look like it should exist...lol

Great info here by the way....I agree with both guys.

 

CID is a product of bore and stroke and the area above the piston at TDC is not in the equation because that area remains constant. Decking the block does not change the bore or the stroke unless you deck it enough that the piston extends past the deck. Decking will change to total volume which will affect the compression ratio.

Using a thick or thin head gasket will not change the CID. Using a large chamber or small chamber combustion chamber will not change the CID. Decking a block and removing the material down to the top of the piston is no different than using a different thickness head gasket and it will not change the CID.

It has something to do with Pi being an infinite number. You can work it out in cc's and will still come up with a decimal number.

 

OK I get it....still seems weird.
I've had a heck of a time since coming to USA dealing with the standard measurement.
It all just seems so primitive. Not to put it down...it works just fine....just not what I am used to or was taught in school.
Thanks for enlightening me about it though.

 

I grew up with imperial measurements and was forced to use metric in the late 70's. My brain thinks in both units of measurements but not in the same way. When driving, I think of distances in kms but I'm following 30 ft behind someone. Many Americans think like this also even though they don't realize it.

Ask anyone the size of the engine in their new car and it's usually in liters. How big is the combustion chamber and it's in CC's. How big is the throttle body and it's in mm. Intake runners are measured in CC's. Valve diameters are measured in inches. Exhaust size is in inches. Street tires are given in metric sizes. Nobody runs N15 tires any more.

My engine is a 540 but I don't call it a 8.85L. My flying toilet throttle bodies are 4.1" each but I don't say they're 104mm.

Hmmm. 885. I could use that as my racing number and very few would understand what the significance is.

 

LOL
kool
I get exactly what you mean.
Growing up we had pounds as weight and ounces etc.
but everything else was metric.
Isn't CC's metric too? Standing for cubic centimetres?
also I recall cars had MPH and also KPH. But the KPH markings were smaller and red numbers and letters.
I now realise that places like walmart you buy meat at like 1.08lbs...It just freaks me out to see it...it's like blatant denial of using the metric system...lol.

Sorry to absent mindedly hijack again....forgive me OP.

thanks

 

Except those of us that have been to 51°N 114°W, 3500' ( Go Flames Go)

44°N 79°W, 651'