GM-GMC: 6.2L Diesel, cylinder head bolts, 700r4 transmissions

Question
Im Looking to Purchase a 1982 Chevy Blazer 4x4 with a 6.2L Diesel. The transmission is a 700r4. I was wondering if there were any bugs with the 6.2 l diesels. I have been told several thing from they were converted from gasoline(which your site fixed) to them being extremely reliable and easy to get parts for.
Thanks,
     Corey Goble

Answer
Corey,

I am glad that my comment about the 6.2 not being converted from a gasoline engine is being read!

Parts are, and will be, available for quite some time to come.  The 6.2 became a 6.5 in 1993 by a change in bore only.  99% of the parts are interchangeable between the engines and the 6.5 is still in production for the HUMVEE.

If the engine is original in the vehicle you are looking at, it will be painted red or orange.  If it has been changed, it will likely be painted black.

The 1982 engines supposedly had more nickel in their cast iron block, but they also had problems with cylinder head coolant leaks.  All 6.2s have issues with the heads cracking between the valve seats.  During overhaul, the heads can be sleeved and the problem is eliminated.

Head gasket issues also exist.  The cylinder head bolts are torque-to-yield and this is a poor choice for a diesel.  Aftermarket studs are available that are much stronger and reusable.  New head gaskets are teflon coated and do a better job of sealing than the original gaskets.

Lastly, the early 700R4 transmissions are weak.  The one in my van failed, but it was my fault.  During rebuild, a 700R4 can be built to withstand more than 600 hp with parts that are widely available for them.  The 1987 and later 700R4s are better, but they will all likely need to be rebuilt at least once in any vehicle.

Ask to see the vehicle with a cold engine and open the hood to verify that the engine is cold (6.2 diesels had block heaters installed at the factory and a seller can plug the engine in and make it start much better than it otherwise might).  The glow plug light should come on and remain on for 5 to 15 seconds on a cold engine.  The engine should crank and start instantly if it is in good shape.  Rough running when cold may indicate one or more bad glow plugs, which can be replaced but are sometimes hard to remove from the engine.  A little smoke is okay, but persistant white, black, or blue-white smoke is a sign of trouble.  Black smoke at high RPM and/or heavy load is okay.

The transmission should shift into all four forward gears smoothly and the torque converter should lock (providing a slightly slower engine speed) on the highway.

You can find a lot of information on www.gm-diesel.com and the site is free to join or to just read the posts.