Motor siezed

After replacing new heads my friend over torqued
the rocker arms. I did not inspect his work because
I trusted him however I tried to start the vehicle  an
within 3 or 4 revolution the made a backfire sound
and stopped. Upon a visual  inspection, the were
10 broken or bent pushrods because  of the over
throwing of the rocker arms. I replaced 10 new
rocker arms  and proceeded to perform 0 lash on
my intake valves by placing the arrow at 12 o'clock
on my balancer. I proceeded to manually turn the
crank over until the crank locked in at the 4 o'clock
arrow on the balancer. I decided to reverse my
turning on The balancer and 3/4 of a turn, around
at the 7 o'clock position it was seized also.
I performed a compression test , by placing  my  
friends finger over the sparkplug  socket , and
there  was compression  except position number 7.
My question is how did I get the bottom motor part
seized in one position and I can manually turn the
crank. And also did the head replacement  and
over torqing on the rocker arms  cause the bottom
end to sieze  and what could it be the stopping pf
the sieze?