I was going to change my Timing belt on my 1990 Toyota 4x4 pickup next week
while I was on holidays since it has 103,000 km (64,000 miles) on the belt.
The engine has 400,000 km (250,000 miles) on it.  I guess I waited to long.
I pulled out to pass someone on the highway and the timing belt blew.  I got
it stopped in a couple hundred yards.  I've got the front of the engine
apart to replace it but ran into another problem I think.

Without the timing belt on, and both cams on their timing marks, I can spin
the crankshaft pulley easily by hand.  There is almost no compression it
seems.  I checked with the local dealer and they say the valves don't get
damaged when the timing belt goes.  If it was a head gasket problem, I would
have thought there would be good compression in at least some of the
cylinders.

 1..  I guess my first question am I right in assuming I shouldn't be able
to spin the crank by hand with the timing belt off?
 2.. If there is a problem, what could be the cause?  If a head gasket
blew, some of the cylinders should still be OK shouldn't they? Since the
timing belt runs the oil pump, could I have damaged the cylinders in that
short of time after the belt blew?