i'm lookin at a 5.0 stang with a bad valve stem or something like that. i really don't know what that is but what he's saying is that its burning oil and gas. i was just wondering how difficult it is to fix/replace this? or about how much would a shop charge to fix it? thanks
To check for worn valve guides, have someone fire up the engine cold while you stand in back of the car. If it puffs blue smoke on a cold startup, the valve guides are pretty well shot. If the valve guides are worn, the rest of the motor is probably not in that great of shape either (worn bearings, poor ring seal). Both heads would have to be removed to replace the guides ($$$$$$$).
Without knowing EXACTLY what's wrong (you don't seem too sure yourself), it's hard to say. Figure both heads will come off, book rate on changing head gaskets alone is very pricey, and add in the work that will need to be done to the heads, and I think it's pretty safe to say you will be WELL over $500.
Again, I'd be damn sure I knew what was wrong with the motor before purchasing the car. You could run compression checks on all the cylinders to give you an idea what you're up against. Only problem is you won't see where you're losing compression (rings/valve seals) if that is indeed a problem.
How many miles are on the car you are looking at? You need to start the motor when it's cold as NKau suggested. Any type of smoke (other than condensation) is a sign.
Blue = Oil
White = coolant
Black = gas
My car likes to send oil through the tail pipes when I shift at 6,000RPMs. But never once lets oil through when I start it up or am crusing down the road. You're probably looking at a rebuild project, but we can't say for sure.
Every motor burns gas or they won't run. If it's buring too much gas (you can smell it at the tail pipes) than the O2 sensors are probably shot. But there is always something else that could be causing it.
Also, any ticking noises the car makes... those can be very bad. Rockers ticking away is OK, but most other ones indicate a motor on it's last legs.
How did the oil, coolant and maintence items look?
Now all that being said, a SBF especially the 5.0L motors are fairly cheap to fix up and get running great. You just have to know where to look. Typical rebuilds can run from 800 on up. New motors start at around 1,300 and up.
The Fox is a great car to own. They are cheap, fast and very easy to work on and learn from.