Things I would look for.
If allowed I would pull a valve cover. Dont see any nasty stuff on top at least someone changed the oil somewhat.
Check the end play on the crank if you can move it in or out a noticable amount the engine has alot of miles on it or someone riding the clutch and wearing out the thrust bearing on the crank. Preferably get a motor from an automatic.
Rotate the crank one way to top dead center. now pull the distributer cap and rotate the the motor the oppsite way until you see the rotor just move. 6-10 degrees is normal, 10-15 degrees milage getting up there. over 15 degrees time to think about a new timing chain usually pushing 100,000 miles on a well kept engine. on a dinosaur motor you reach this point around 70,000 miles. Over 20 degrees you have to think about walking to work soon. if the rotor doesnt turn welll you turn and run away.
Look for corrosion in the coolant system, a system not taken cared for it will show it.
look in the exhaust system on an efi motor it should not look oily.
pull the plugs they should all look the same a nice light even color.
You could look around and see if you can rent a bore scope and look down in the spark plug holes.
Look for corrosion around the freeze plugs.
look for a paint color change on the motor and overheated motor will usually show heated paint especially around the exhaust ports.
pull the oil fill cap and smell it, an oil starved motor will smell burnt.
If your looking at a motor in a car avoid a motor from a car that looks like a pig owned it. avoid a roll over motor funny things can happen to a motor upside down and full of fluids. look for signs of maintainance tags or oil change dates they are signs that things were periodicaly looked at. Look at the tires and peddals in the car, if they are worn excessivly the car has alot of miles on it. Look for a tow hitch. High end cars are usually taken care of better than low end cars. sport models and pick-ups are driven harder than other models.
Remember there is a reason the motor went to the scrap yard, find and evaluate the reason. You want a motor that came from a low milage car that got rearended not one that came from a low milage cherry car sitting in the yard which likely starved from oil with a rod knock.
A better detective will usually result in a better find. Hopefully you will find a low milage Lincoln with a blown transmission.
if it looks like a pig and smells like a pig you can assume its a pig.
