My dad bought a 87 Sammy it has the 1.3L of course. It has a miss to it. It seems to not have very much power. We were told it was a blown head gasket, but it doesn't have water in the oil. What could it be?

Oil in the water would be obvious for sure, but not the only way to tell.

Do a compression check.

Are there bubbles in the radiator water?

Check the plugs, do they all look dry and the same?

Are the wires and cap-rotor good? Easy place to start and check the coil too.