Dave
I put links to two different home made leak down testers, plus the one from Longacre. I was just looking at the one in the photo and I don't think that one would work. If you compare the gauge location to the drawing in the second link, you will see that the gauge is on the wrong side of the restriction orifice. The orifice has to be between the 100psi supply and the gauge that you read the pressure loss.
If you built the first one, I am sorry for the confusion. Add a "T" fitting between the orifice and the female quick connect and move the gauge or even better add a second gauge. The gauge on the regulator does not have to be a 100psi gauge. Anything over that will work fine. Set the regulator at 100psi and take the reading on the other gauge on the engine side.
