Date:         Wed, 13 Mar 1996 01:01:41 -1000
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         rsthj@aurora.alaska.edu (Thomas Johnson)
Subject:      Re: new heads

Hi Bob, hi All,

Just two cents of clarification and an alternative.

>Get a 50cc syringe from a vet or pharmacy, level the head and do a rough
>check of the chamber volume.  The object is to get a reasonably accurate idea
>of their volume.  Do all four.  Take their average.  Use it when computing
>your compression ratio.  (If the chamber is larger than 50cc, put a  marble
>in it.  Use the same marble in all four chambers.)

It is important to account for the volume of the marble when calculating
the compression ratio.  The volume of a sphere is
(4/3)*3.14159*(diameter/2)^3 .  e.g consider the following:  chamber
volume=50 cc's, stroke=6.9 cm, bore=8.5 cm, deck height=.06 in, marble
diameter=1.5 cm.  Neglecting the volume of the marble, the compression
ratio is 7.68:1.  Including the marble, the compression ratio works out to
7.48:1.

An alternative to measuring the volume with a syringe or a burette is to
use an electronic scale.  One cc of water has a mass of one gram.  (Of
course, a syringe does only cost 99 cents.)

-Tom