Saying a car has a bad head gasket is a default description that is frequently miss applied to various ills.

For engines in general, a head gasket can fail in these modes, listed most frequent to least.

Cylinder to coolant ( Possibly what your issue is )

Cylinder to cylinder

Coolant to outside the engine

Coolant to oil / oil to coolant

The _only_ way to test for cylinder issues is to do a leak down test. This is accomplished my removing spark plugs, turning a piston to top / both valves closed then pumping in about 100 PSI of air. You then look in the rad cap to see if the level rises or bubbles form. If is does, there is a breach between the cylinder and coolant. This can be a bad head gasket , cracked head. Cracking a block ( cylinder ) on a regular engine is exceedingly rare.

Any other method will be inconclusive and non productive.

Pressurizing the cooling system will uncover coolant to outside of engine. Coolant / oil issues will be apparent by looking at each fluid.

Also be sure to pull the hose from the automatic transmission vacuum modulator, it can fail and allow transmission fluid to be burnt causing smoke.