[VB] Help! Locked Up Engine that Ran 2 Weeks Ago - Puzzler

[Avocado Tom Tarka]

Greetings Volks!

I just found myself in a bit of a bind, where my engine which ran when I
pulled it two weeks ago will no longer turn over.

I'll run through the whole saga for completeness but the basics are that I
pulled the engine to replace the transmission and ended up pulling the 3/4
head as well because the #4 spark plug broke off in the head.  I just
torqued the 1/2 head (I usually torque the heads when the engine's out if I
can), and when I went to set the valves: no go.  The engine doesn't turn
over by hand (with or without the rocker arm on).  The 3/4 head is still
off, as my plan was to put it on tomorrow.  Help?

    - Tom
(full disclosure: I'm cross-posting this to thesamba because I'm a little
freaked about needing to get this engine back up and running)

Full Story is as Follows:

Background:
Bus is 1967 with stock transmission.  Engine is 1600 SP I rebuilt ~35,000
miles ago.

My plan was to pull and replace the transmission on my 1967 bus.  I figured
I'd do a compression check before I pulled the engine, just to see if I
should be tackling anything else while the engine was out.  I recalled that
the compression on #4 might be low, but my notebook is currently MIA.

Compression was good on cylinders 1-3 (115, 112.5, 115).  When removing
spark plug #4 to check the compression: it broke off.  Doh!

[u]The Saga[/u]
1. Pull engine.  Pull 3/4 head.  Remove broken spark plug base with
extractor.  Take head to the machine shop to check threads and valve guides.

2. Clean outside of engine and check endplay.  It's at 0.009" (no surprise
there, I knew it was off).

3. Attempt to remove gland nut: no go without the engine being in a more
stable place (instead of on blocks).  Decide to wait until the engine is
back to a longblock, then deal with it.

4. Clean off built up carbon from the top of the #3 piston.  Can't recall
if I did the #4 piston or not.  Currently, the #3 piston is close to TDC
with #4 all of the way in. (This seems like it could be important or could
be a red herring...unclear, but I thought I'd call it out.)

5. Pull the rocker arm from the 1/2 head and torque the head nuts, first to
~7 foot-pounds using the initial sequence, then to 22.5 ft-lbs using the
second sequence.  None of the upper nuts move in either tightening
sequence.  The lower nuts, particularly the middle two, do tighten during
the second sequence.

6. Reinstall push rods and rocker arm after cleaning. Remove flywheel
lock.  Attempt to turn the engine over by hand from the pulley: engine
doesn't move more than 1/2 inch.

7. Remove rocker arm and push rods (in case I screwed something up) and
attempt to turn over engine.  Still no dice.

I'm at a loss.  If I had adjusted the end play, I could see the engine
being locked up (I've had that happen before).  I can't imagine that
torquing the heads would have any impact though.

My best guess is that the base of the #4 jug moved a little forward or that
somehow one of the rings on the #4 piston got caught on the edge of the jug
somehow.  It seems really unlikely that that might be the case, but I just
can't think of anything else?

Any ideas?  Engine has oil in it, and like I said: it ran fine when I
pulled it, has decent compression (for a 7:1 ratio), etc.

Thanks!
  Tom
---
  "We are MoTown.  We are professionals.  We're here to get the job done."