so just bought my 94 sc300 from a guy who said the head gasket was blown. Went and picked it up tried to start it and after two cranks it makes like a floop back fire sound but no burn if that is a decent description lol but he had replaced some plugs for the alternator, spark plugs and wires and things and I’m wondering if it could just be off time or plugs be wrong somehow

No smoke oil is clean coolant isn’t disappearing I have spark and fuel and all six cylinders have 190 ish psi compression checked what else could be making the car act like it’s head gasket is out but isn’t