TOPIC:

I currently have my cyl's, pistons and head at a machine-shop so this is fresh in my mind.
All the comments are correct.
I'll toss this into the pot.  If you can't make one you may know someone who can. 
Or this - More practical for most: 
Head On:   It will be a lot less work in the long run and will alleviate potential problems and issues that WILL arise  if you do a tear-down. 
For what it's worth:   

scotch wrote:

I currently have my cyl's, pistons and head at a machine-shop so this is fresh in my mind.
All the comments are correct.
I'll toss this into the pot.  If you can't make one you may know someone who can. 
Or this - More practical for most: 

Head On:   It will be a lot less work in the long run and will alleviate potential problems and issues that WILL arise  if you do a tear-down. 
For what it's worth:  
 

Nice video but he doesn't explain how the valves are supported. I think people normally put rope into the cyclinder through spark plug hole and then apply pressure at the crank to compress the rope between the piston and valve

The Lisle plunger style tool is cheap and both removes and installs the keepers in seconds.

 The work on my 13 is progressing, all be it slowly. I stupidly dropped one of the small rubber pallets that sit on the tensioner shaft, and it disappeared down into the deapths of the engine.  They sat in the recess marked with yellow dots in the photo.This necessitated in me having to drop the sump, and all the extra work that entails. Stupidity definitely has a price. I eventually did find it, and I also found a partially clogged mesh screen, so the extra work wasn’t a complete waste of time. I was surprised by how much dirt there was caught up in the mesh. I am getting there. 

Some things happen for a reason so count your blessings here. That screen looks to be 40% blocked. Yikes !! I also like to "analyze" the crud to understand what's contaminating the oil. Looks like a couple of pieces of silicone gasket maker (the beige colored items) The red and green pieces are interesting. ??? The black looks carbon like but maybe not??? 

Another good opportunity now to check your primary and secondary drive chains for wear. (slack)

The red and green pieces look like bits of old gasket sealant, strangely the black stuff is bit of leaves, as in off a tree. There also seemed to be a lot of fibers in there which looked a bit like animal hair. The only explanation I can think of is that someone in the dim and distant past has filled it up with old contaminated oil. I have now removed the valves, and some of them took quite a bit of pressure before they popped off the spring retainer. I don’t think I would have managed without a valve spring compressor. The old valve stem oil seals looked in pretty bad shape, one of them wasn’t even there. Took the springs out and there was no oil seal to be seen, no wonder the poor old thing burned oil.