Probably the reason why everyone is listing the same part number for both 1.9l and 2.1l heads is that the 1.9l heads are no longer made.  Everyone has been putting 2.1l heads on their 1.9l engines for a while now (if you are putting new heads on).  I did it last year on an 85 Westy I was getting ready to sell.  Made no difference in the power of the engine that I could tell.  Felt like a normal 1.9l.  This was when I found out about the 1.9l heads being discontinued.

Hope this helps,
Ken Wilford
John 3:16
www.vanagain.com

-------------- Original message --------------
From: Evan Mac Donald <macdonald1987@SBCGLOBAL.NET>

> I am currently rebuilding a 2.1L into a 2.2L, and converting it to go into a
> 1.9L spot in an '85. I have problem, though...
>
> I have found conflicting information regarding the Cylinder heads between 1.9L
> and 2.1L waterboxers. Are they indeed the same? Are the chambers the same
> volume? The 2.1 heads I have both have a LARGE crack between the valve seats...
> ...larger, I think, than the Bentley says is allowable. I have a set of
> "original" 1.9 heads from an '84 that may need to go on in their place. I do
> not want to raise my compression ratio - no premium for me, thanks!
>
> Everywhere I look to find new/replacement or rebuilt heads list the same
> number for both.
>
> Thanks to all!