Locked Up Engine that Ran 2 Weeks Ago - Puzzler

[avocado_tom]

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?

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. 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!

The Saga
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!
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"You realists can stay the hell out of our office." - D. Dudas

[Tizian]

This is my best guess:

Since you tried to pull the wheel with head 3/4 off, one of the cylinders could be tiltet causing the piston to jam. Put the head back on and tighten the nuts carefully. Then try to turn again…

[avocado_tom]

[BarryL]

Did anything fall between the flywheel and block? Distributor was never removed while turning crank? Ground electrode or center electrode fragment fell into piston top gap?

[Glenn]

Pull the head. Use some deep sockets over the head studs and put the washers and nuts on. This will prevent the cylinders from moving.

Now try rotating the engine.
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Glenn
74 Beetle Specs | 74 Beetle Restoration | 2180cc Engine
"You may not get what you pay for, but you always pay for what you get"

Member #1009

#BlueSquare

[avocado_tom]

And...I figured it out!

A couple of the case studs for the head had pulled out when I pulled the head.

I installed them too deep when I put them back in, which was immediately after I pulled the head (2 weeks ago, but which seems like a lifetime ago).

Engine now rotates freely.

Thank you all so much for the ideas and support!
_________________
"You realists can stay the hell out of our office." - D. Dudas