Just finished rebuild using the video series, thanks!
BUT, I double checked the book and it looks like I forgot to install the two dowels between the cylinder and the head. These are the two non-tapered pins, not the tapered oil pins at the bottom.
I went back to the video, and I am 99% sure you didn't install them in your rebuild either. They are not visible when you put the head on. (I really hope they were not slipped on off camera - too cruel).
Please someone tell me these two parts are not critical? (As if anything in the engine is just 'extra')
Hopeless post, but worth a shot before I tear it back apart.