Hi Bob & all

>You can prop the throttle open if you wish.  Drawing fuel thru the carb isn't
>a problem when all of the spark plugs are removed.  With the plugs pulled the
>intake manifold is effectively at atmospheric pressure regardless of the
>position of the throttle plate.

>I've heard it can make a difference but I didn't see it when I tried it both
>ways.  This may be a hold-over from working on V8's, or because some
>mechanics don't pull all the plugs.

>But I'd open the throttle if I were checking compression on a one-lunger :-)
  
Bob, the last line left me thinking (always a dangerous state of mind :)

Only one inlet valve is open at a time (ignoring overlap). So even if the
plugs are pulled, the cylinder you're measuring is open to the inlet
manifold, which is closed everywhere else (with the throttle closed, of course).

OTOH, the internal volume of my (1700 FI) inlet manifold is quite a bit more
than the 425+ cc max volume of the cylinder. I would tend to say that the
size of the inlet manifold could make a difference. But I've never tried it
both ways, I learned to do compression tests with the throttle open and the
coil disconnected.

The important thing is probably to do the same for all four cylinders and
look for the same results.

CU

Wouter