But wait, there's more.

When using a cylinder compression hose as a cylinder leak down tester, you must remove the check valve at the spark plug side of the hose. The valve is usually a tire valve core.

Also, you will need to rotate the engine so the cylinder under test has the piston at top with both valves closed before you apply air. When doing this, apply a bit of air at first to make sure the motor does not roll over. ( Keep clear of belts and fan. )

The engine will roll over with some force when not at TDC and air applied. So if you were able to roll the motor over by hand, no air was entering the cylinder.

Really rough calc below:

3.5" bore at 100 PSI = 962 LB force ( PI * R^2 = area^2. area * PSI = LB force )

3" stroke = 1.5" lever with 962 LB hanging on it = 120 Ft/ LB ( with the crank at 90* )