Not necessarily. The leakage will be a little more pronounced at the top of the stroke, where the most wear is, but on the one with the rockers removed, just pressurize the cylinder and let the piston bottom out. Then listen for leaks at intake, exhaust, and crankcase. With the manifolds off, you can even pinpoint which valve is leaking. A leak at the thermostat housing would indicate a blown head gasket.
Jerry
