Hey guys I got this off a ford truck forum and found it interesting because of the fact that the formula works on everything but a 4.6(281CID)

{"Formula to Calculate the CID (Cubic Inch Displacement) of an engine
R² × Pi × H × number of cylinders = CID (Cubic Inch Displacement)

In other words;
Radius of the bore squared × 3.14 × Stroke × number of cylinders = CID

For Example:
If we have a V8 engine with a 4" bore and a 3" stroke, the formula would read: 2² × 3.14 × 3" × 8 = 301.44 CID

In other words;
2² (The radius of a 4" bore [2"] squared [multiplied by itself, or 2 × 2] × 3.14 (Pi = 3.1416) × 3 (3" stroke) × 8 (The number of cylinders in this engine) = 301.44 CID

This engine, by the way, is the Ford 302! This formula will work with any engine.

For example, the Oldsmobile 350 V8, which has a bore of 4.057" and a stroke of 3.385" would be; 2.0285² × 3.14 × 3.385 x 8 = 349.88742333922 CID

A Ford 351 with a bore of 4" and a stroke of 3.5" would be; 2² × 3.14 × 3.5 × 8 = 351.68 CID"}

Now as for my math this is what I get for a 4.6 (281)
bore is 3.55 and stroke is 3.54
315.68 CID

The formula that states bore x bore x 0.7854 x stroke X #cylinders = 280.31 for our 4.6. It works also for every other engine and gives the same sum as the formula shown on the truck forum. So why the difference in displacement for the 4.6 then? You do the math. You will see what I'm talking about.

 

The formula works, you just made a math error. Did you divide the bore by 2 before you squared it?

 

i got 280.311 (w/ some rounding)

 

Yeah i figured it out last night just after i posted it. It works. Math error is right. Thats why I don't build rocket ships anymore.