I'm measuring the volume of the combution chamber, that is, the volume
occupied by the space "above" the plane where the heads touch the top of
the cylinder walls.  There's a definite combustion chamber, i.e., a
machined out area which contain the valves and into which the fuel/air
mixture is compressed.

Maybe you're referring to the plane where the heads touch the top of the
cylinders; in the original VW heads this is a flat plane from the spot
where the head/cyliner meets until the combustion chamber is formed,
while in the AMC heads there's a "step down" immediatly after the point
of contact.  (The information above is my speculation, based on what
various people have told me about various things.)

  VW head:

    |______                              _______|
           |                            |      ^
           |______Valve_____Valve_______|      |
                                               |
                                          Cylinder goes here
  AMC head:

    |__                                       __|
       |                                     |
        --                                 --
          |                               |
          |______Valve______Valve_________|

The AMC head has more volume because of its geometry, hence, no need for
shims.

(Again, the above is mainly speculation.  Feel free to correct.)

On Fri, 30 Apr 1999, kenneth d lewis wrote:

> Maybe I am misunderstanding you. What are you cc-ing in the head?
> It has been a while since I had one apart. I thought the top of the
> combustion chamber was basically flat. You're not cc-ing volume that is
> occupied by the cylinder wall are you? Otherwise I think you should
> rotate your engine vertically and cc a cylinder with piston at top dead
> center.

---------------------------------------------------------------------
Tom Young               young@sherlock.SIMS.Berkeley.EDU
Lafayette, CA  94549    '81 Vanagon
---------------------------------------------------------------------