I'm looking at buying an 87 GMC 3/4 with a 6.2. Is there anything I should look for and/or stay away from with these engines? Any tell tale signs to indicate whether it's in good/bad condition?
Thanks.

I am going to look at some 6.2L Burbs and I am wondering the same thing!

Thanks,

Michael

Usually same basic thing. Id find out how new batteries are. would be a pain to buy a truck and have to immedately spend money to buy 2 new batteries. check to see how it starts. how clean is it under the hood? check dipstick to make sure oil is okay looking. run the engine, sounds okay? notice any weird exhaust? check for oil/fuel leaks under. if a pickup check fuel tanks, they are prone to rusting between the tank and shield. ask how often oil been changed.(should be every 3,000) try to notice if glow plugs are working(watch for a large drop on the battery guage on the dash on statup)

With the engine running, pull off the oil fill cap and see how much blow-by. If little to no blow-by and a good maintenance record, buy it.

Can you explain blow-by? I think I know what it is but I want to know for sure.

Thanks,

Michael

I was going to mention it but I dont know enough about it to tell people what to look for. it is some sort of vapor from the crankcase.

maybe someone can explain what exactly it is, what causes it and the side effects, ways to correct?

Blow-by is high pressure combustion gasses blowing past worn out rings into the low pressure crankcase. In addition to gasses coming from under the PCV valve, if the rings are worn you'll also probably see blue smoke with the engine under a load if someone is following you. Blue smoke on start-up or deceleration (high vacuum) is generally from valve guides/seals. Engines with worn rings tend to have more external oil leaks (i.e. oil pan) too from positive internal crankcase pressure trying to push oil out the gaskets. ;)
If the rings or valve guides are shot there is no cheap easy fix.
REBUILD TIME -:t

In addition to gasses coming from under the PCV valve, if the rings are worn you'll also probably see blue smoke with the engine under a load if someone is following you. Blue smoke on start-up or deceleration (high vacuum) is generally from valve guides/seals. Engines with worn rings tend to have more external oil leaks (i.e. oil pan) too from positive internal crankcase pressure trying to push oil out the gaskets.
If the rings or valve guides are shot there is no cheap easy fix.
REBUILD TIME

Only a couple of notes. On a diesel, smoke on start up can also be caused by bad glow plugs. It will be blue just like oil smoke. It can be hard to distinguish
oil smoke and ordinary smoke on a diesel, so your best bet is to pull the oil fill cap with the engine running and look for crankcase vapors puffing out. If it's puffing hard, it's worn out.

Thanks,

I will definately check that!

Michael

One other thing, with the engine cold, remove radiator cap and then start engine. Make sure radiator is all the way full before performing test. Allow engine to warm up while looking at the coolant. No bubbles in coolant=good lots of tiny bubbles in coolant=bad could be head gaskets starting to go or combustion leaks from cracks between valves.;)