How do i tell if i have blown head gasket - 1994 Pontiac Firebird

This may be impossible without disassembly. If you were lucky and the crack is external, you could observe where leak is, but internal only leaks can be from a blown head gasket, cracked head or cracked block. Most common is head gasket, next head, and last block. Since anyone of these can cause water to enter the oil circuit, or oil to enter water, I know of no way to tell which is bad without a teardown.

Oil and coolant mixed usually means the engine is damaged.
Blown head gasket, or cracked block - head.
You may have coolant in the engine oil too.
I would not drive it.

The best way to tell if a head gasket is blown is to buy the test kit from AutoZone, Advance Auto or NAPA and test the radiator fluid for combustion gases. This is a very positive and determing test that leaves very little doubt. There are other ways to test for a blown head gasket but this is the easiest and quickest way and the test kit is easy to use, you don't have to be a mechanic to use it.
Hope this helps.

You can't tell untill you get it apart. and then some times you still can't see a crack. It needs to go to a machine shop to be checked. I send them all out to be checked when I do a head gasket replacement.

Hard to tell if its a blown head gasket or warped cracked head. The symptoms will be the same. The way to check is to pull the spark plugs and look at them. If one is super clean then more then likely antifreeze is getting in that cylinder. You can buy heavy duty sealant to try to seal the leak up. You get this at a auto supply depot. Get the one that you have to drain antifreeze and replace with water. You run the engine with the spark plug removed from the cylinder that was leaking until no water comes out

Maybe a blown head gasket,cracked head or a cracked block.... A mechanic can probably tell by doing a compression test

There is really no difference between a blown or cracked head gasket. In either case the gasket would have to be replaced. Generally the term "cracked" is used when referring specifically to the cylinder head/s its/them selves. If the cylinder head is cracked it is a much more expensive repair.

a cracked head or blown head gasket,will cause your vehicle to have a miss in the cylander where the crack is or where the gasket is blown. you can also see coolant leaking if the gasket is blown. you can also see water in the oil,and white smoke come from the exhaust.
to tell for sure that the head is cracked,and not just a blown gasket is to remove the head. you will instantly see if the gasket is blown. if its not,then turn the head upside down and look at the small space between the valves,as this is where 99% of cracks occur.

Often (but not always), a blown head gasket will also cause deposit of water on a piece of cardboard held an inch from the tailpipe output while the engine is running (when this is happening, it is likely that the catalytic converter has been ruined and the muffler will corrode in short order as well).

Sometimes drops of water will be seen dropping from the end of the tailpipe. Another clue: turn on the heater; often when the head gasket is blown an odor of antifreeze and synthetic rubber will emanate from the heater vents.
Many of the symptoms of blown head gasket can be caused by some other problem in the cooling system, without the head gasket being damaged. Conversely, other problems with the cooling system can cause a blown head gasket and/or warped head.

When checking for a blown head gasket, one of the most common tell-tale signs is a milky-gray ring around your oil cap. When coolant enters the engine oil through a crack in the head or through a blown gasket, it evaporates and leaves a milky ring around the oil cap. Another easy way to tell is to check your oil dipstick. Change your oil and pull out the dipstick. Make sure that you take note of how far up the dipstick the oil is. Top off your cooling system and fill your cooling reservoir to the top. Screw radiator cap back on and start engine. Run engine for about 20-30 mins. or until it reaches normal operating temperature. Allow engine to cool (engine must cool completely to get accurate oil reading!!). Check oil dipstick again. If the oil has a watery appearance and has risen noticeably up the dipstick, the you probably have a blown head gasket or a warped head. Also look for a dripping, sweet-smelling liquid coming out of your tailpipe. Any of the above symptoms could be the result of a blown head gasket. The easiest way to tell is with a compression meter. This replaces the spark plug and lets you know what compression each cylinder is running at. If your compression is abnormally low, then you have a blown head gasket or a warped head. (note: consult repair manual for appropriate compression of each cylinder.)

White smoke is coolant being burnt. That with your lose of power would suggest a bad head gasket. A compression test could confirm it. Hope this helps.