No, you can't change a 1.9 into a 2.1 simply by installing the
crankshaft from a 2.1.  When you put a longer stroke crank into an
engine, the pistons travel farther. Half of the additional stroke is at
the bottom of the travel and half at the top.  That means the piston
would hit the head before it reached full travel. Either the rods must
be changed to shorter ones or pistons must be changed to ones that have
the piston pin closer to the crown. In either case they must differ by
half the increase in stroke and a little more to keep the compression
ratio the same unless the piston crown is modified also or the head
combustion chamber volume is modified.

On aircooled VW engine spacer shims are often used when longer stroke
carnks are fitted. This is not possible with a waterboxer since the
water jackets would then be too short.

Mark

 John Rodgers wrote:

> Paul, thanks.
>
> You answered my main question.
>
> Regards,
>
> John Rodgers
> 88 GL Driver
>
> Paul Guzyk wrote:
>
>> Yes, the heads are the same.  You can make a 1.9 block a 2.1 by
>> changing the crankshaft.  (the cylinders are the same, just the
>> stroke is longer)
>>
>> However, your machine shop will have to grind a bit off of the
>> connecting rods (then ensure they are balanced) so they don't hit the
>> 1.9 case (the 2.1 case has a little more room inside).
>>
>> You may just want to look for a good used 2.1 case and crank and use
>> your pistons, heads etc.
>>
>>
>>> Question:  Can the 1.9L engine be upgraded to an essentially 2.1L
>>> engine
>>
>>
>> simply by changing a few parts......like cylinder barrels, pistons, etc.
>>
>>
>