On Fri, 13 Jul 2007 04:50:07 -0700, JR wrote:

I sometimes get water in my 4.3L motor oil after it sits a week or
more and at least once have had it get in one or two of the cylinders.
Pulled the exhaust manifolds and they look good, filled them with
water and no drop in water level and it has been a week. Compression
is great (192 to 198 in every cylinder) - Vacuum is perfect. Any ideas?

The usual suspects are risers, manifolds or head gaskets.