Car math and and rules-of-thumb

Is this a tech post? I dunno, but I thought it would be handy to compile all those useful little formulas and thumb rules into a single thread. For example:

Engine displacement = bore^2 * stroke * 3.14159 * # of cylinders / 4

Coil spring stiffness = (constant) * (wire diameter) / (coil diameter^2 * # of coils)

Street carburetion CFM: twice the displace in cubic inches, less 15% (e.g. 350 * 2 *.85 = 595 cfm)


Got any of your own? Let's see 'em.

 

Every project will cost tripple what was initially expected, and take twice as long to complete!