John Bange wrote:
> I think the only changes between the 1.9 head and the 2.1 were
> structural. According to the Pro Training Manual, the 2.1 simply has a
> 7mm longer stroke (94mm piston, so 4.7 * 4.7 * pi * .7cm * 4 cyl  =
> .195 liters).

Toward the bottom of the page in the following link, Ken Lewis talks
about the effect on Compression Ratios Using 1.9L Heads on a 2.1L Engine.

http://neksiwel.20m.com/custom.html

Seven years ago I bought a new AMC 1.9 head but they've since become
NLA.  2.1 heads will work on a 1.9 but offer a slightly lower
compression ratio.

Mike