comp ratio calcs
Turbo Mini Forums

Well more like a rough guess really, this is how it works in my brain, bit rounded up to get rid of all the decimals but is it about right? was thinking it was gonna be a bit higher!
73.5mm bore = 1380cc
1380 / 4 = 345 cc per cyl
345cc / 81.28mm stroke = 4.244 cc per mm
piston 1.3mm down bore =4.244 x 1.3=5.5cc
gasket compressed? 0.75mm =3.1cc
Piston dish 9 cc
head 28 cc
so i make it closed = 5.5(deck) +3.1(gas)+9(pis)+28(head)
45.6cc
open 45.6 plus 345
390.6
so 390.6 /45.5 =8.565?
comp ratio of 8.5 :1? Is this how it works or am i being a dumb ass?

Calcs are correct. You could add 1cc-ish for your ring lands. which would fetch it down to 8.4:1

If something is worth doing, it's worth doing half of.