It's time for pride to stand aside again in the interest of honest mechanical academe
The first time I tested compression was in the 70's on a mustang 5 liter or equivalent.
Then I in 2008 I bought a set for diesel but could never get good results with it because it had no check-valve and all I could do was guess just how high the needle went in a split second. Haven't used it since, until the other day, when I did notice an L-shaped adapter which I figured must be for hard to reach places, the way that grease-gun L-adapters do. I decided to try it and lo and behold IT is the check valve. So it's back to compression testing the next time the weather lets up.
I haven't run the engine much seeing that I don't even have reliable oil-pressure indication but every time I do anything at all the run improves. Just cleaning out the one injector that I gutted to make an adapter made a difference after reassembly and reinstallation. I expect deliveray of an injector test kit in early December. The engine sure seems to need work but that will be coming ANYWAY, once I decide yes/no on a 913. The main thing is that it revs to 3000 and nothing seems broken or bent, pops and farts don't phase me at this stage. It means I have a good core to either build or trade for a blown (maybe cooled) 913 good core to build (another thread I think).