cometic compressed volume
Turbo Mini Forums

the cometic head gasket is stated as 030" i take it thats the gasket thickness, what would this be in cc? any ideas in working this out?

(Bore size of the gasket/2)^2 * PI * thickness will give you volume (all dims in cm to get cc)

Edited by Tom Fenton on 6th Aug, 2010.

0.03" is about 0.76mm so assuming the fire ring diameter is 74mm (I assume they size it for the biggest possible bore) then
(((Pi X d^2)/4) X t) gives 3.3cc

EDIT - Tom beat me, only difference is he did Pi r^2 whereas I did Pi d^2 / 4 (same thing, just different way of writing it)....

Edited by Rod S on 6th Aug, 2010.

Schrödinger's cat - so which one am I ???

Blimey Tom do i look that intelligent!

its 73mm Rod

Neil, there are two cometics, slightly different thicknesses and bores,

if yours is 30 thou then it is the one with the larger bore to clear 74mm bores.

anyway the cc will be jsut a shade over 3cc

Schrödinger's cat - so which one am I ???

Joe i could only find one on there site

theres the C4148-040 too, its listed under midget, thats what I was running as I'm at 73.5mm bores.

cool cheers joe

btw the 40 thou gasket will be about 4.3cc

cometic do different thickness gaskets depending on how many layers you want. a 3 layer (standard) is about 30 thou. I had a 5 layer on my old KAD head. that was about 55 thou. They seem to be able to do what ever you want. I needed it to bring my compression down a touch.