i just bought a 78 chevy truck engine with 80,000 miles on it, before i throw it in, i would like to know some tell tale signs of burning oil.......this way i know if i need to rebuild/ get new heads or not

keep in mind the engine is not running, as its not in a car currently

so dont say blue smoke

 

about all you can do is leak it down. be a safe bet you need to replace valve seals.

 

how do i do a leakdown test?

fill a cylinder with gas, come back later and see if the level is down any?

 

Look in the exhaust ports for oily residue

 

I think what Ede was refering to was a differential compression tester. (also refered to as a leak-down test)

It's set up like this:
Air-compressor air is press regulated to 80 psi or so.

A "primary" gauge monitors the regulated press.

Air then travels thru a jet (a small hole calibrated for cyl size).

After the jet, the air press is monitored with another press gauge (secondary).

The air is then sent to a hose that screws into the spark plug hole.

With the cyl being measured at top dead center on the compression stroke, the secondary gauge press should be a certian value.
The spec is listed as a differential press between the primary and secondary gauge pressures, thus the name "differential press gauge/check".

A side benefit of using this method is that you can listen at the carb, exhaust and oil filler hole to see where the leak is.

The diff comp test doesn't check the oil control rings or valve seals, but will give you a good idea of compression capabilities.

As for the easy stuff, like RB83L69 said, check for oily build-up in the exhaust ports.
Might pull PCV and make sure it's doesn't have oil running out of it.

I'd also pull a valve cover off and check for general cleanliness.
Check oil drain-back holes for sludge build-up, a sure of sign of oil not being changed regularly.