All right, so here's a little catch-up. Things are going pretty slowly here because I've got almost no time free to work on this and also I'm waiting for parts.
I did manage to get both heads off and the problems with #2 and #7 are pretty plain to see.
#7
#2
Another thing of note to happen was that I actually found a source for 17/32" tubing. I'd previously been opening out 1/2" tubing by forcing it over some old head bolts. This did expand it but left it uneven. The 17/32" stuff arrived today and it's night and day.
I also determined the right length. The actual hole depth is 3.5" on my Edelbrock head. After doing my first tube this length I was in the awkward position of having to try to trim it. The tubes I'd done when the head was in I shot for about 3". That in fact proved too short for good coverage. 3.25" seems about the sweet spot.
3.25 inches is the right length
17/32" is the right diameter
I'm mainly making these notes for the sake of the next guy..
There's more to tell but you only get four pics per post.