About six years ago I needed to use my leakdown tester that I had loaned out. I have tons of junk laying around so in about a 1/2 hour I made one. Still using it because the one I loaned out, never made it back home, and it works great,
I used a small piece of fuel rail, plugged off the center between two fitting holes and installed a .040" jet between them. I guess it could have just drilled it to .040" but I trusted a jet to have a much more accurate hole than drilling the hole.
I installed a matched pair of 160 psi gauges on each side of the jet and one of those small regulators on the one side and a air hose fitting on the other so I I could use the hose off my compression gauge on it.
It served the purpose very well. I later compared it to a friends Snap-On and it was within a couple of pounds, so I have just kept on using it rather than get another.
