Roger;
        This is news to me. I thought both heads were the same. The
Bentley refers to ONE head for both engines. Anyway, here are some
formulas so you can decide for yourself. First some definitions:

Squish volume= The volume in the cylinder when the piston is at top dead
center.

Cylinder volume= the volume swept by the cylinder i.e.  2.1L=525cc;
1.9L=475cc

If memory serves me compression ratio is given by the following formula:

C.R.= (Cylinder volume+Squish volume) / Squish volume

Solving for Squish volume I come up with:

Squish volume= cylinder volume/ (C.R.-1)

Assuming a compression ratio of 9:1 in both engine;

Squish volume for the 2.1L= 65.625cc
Squish volume for the 1.9L= 59.375cc

This supports your claim of approximately 5cc difference between heads.
Now lets recalculate using 2.1L volume and 1.9L squish volume:

C.R.=(525+59.375)/59.375

C.R.=9.84:1

There is one important piece of data we may or may not need to take into
account; the 2.1L has a longer stoke. So how much of that change in
squish volume is due to different heads and how much is due to different
stroke? I will leave that question open for debate.

        FWIW let's calculate stroke assuming the heads are the same.
Bentley only mentions one piston for both engines; 9.4 cm in diameter. I
come up with a stroke of 7.565cm for the 2.1L and 6.8475cm for the 1.9L.

        That's enough math for tonite, I still have to go out and finish
installing the relays to boost the voltage to the headlights on my
transporter. I will mull these figures over and get back with you.

Drive Safely & Good Luck
Ken Lewis<Kernersville,NC>86 VW crewcab;60 T-5 Coupe

On Thu, 14 Oct 1999 21:35:24 EDT Roger&Zoe Ann Banker <Vantaztik@AOL.COM>
writes:
>Hi all.  My local mechanic (a reputable fellow) rebuilt an engine 6000
>miles
>ago with 1.9 heads on a 2.1 engine.  The cc loss is minuscule, maybe
>5cc, but
>the compression goes way up to 180.  According to the Bentley, up to
>189 is
>acceptable, so this looks good.  I rode in it today, a standard 1987
>Vanagon,
>and the power increase was quite noticeable.  It runs smooth, no
>overheating,
>no problems.  Now mine is being rebuilt, and I told the mechanic to
>get 1.9
>heads for my 2.1.  Has anyone tried this?  Aside from the need for
>premium
>gas, are there any drawbacks?  I am only interested in low end power,
>so I
>don't want big valves, ratio rockers, hot cams, or any other stuff
>that needs
>high rpms to be effective. I am also getting a performance exhaust
>system
>from Fast German Auto.
>Will this set-up work well, and are there any other low end
>performance
>goodies I am overlooking?
>Roger & Zoe Ann Banker
>1987 Syncro Adventurewagen

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