Re: 6.2L Diesel

Posted by jdemaris on February 02, 2009 at 06:47:57 from (67.142.130.32):

In Reply to: 6.2L Diesel posted by 4320diesel on February 01, 2009 at 17:59:18:

I've got over 20 trucks, Suburbans, and Blazers with 6.2s. My longest runner was in my 3/4 ton 4WD 87 Suburban that pulled a small livestock trailer and lasted to 520,000 miles before it blew to pieces.

Here are a few things to keep in mind.

The 6.2 was designed originally to have the same horsepower and torque as the 305 gas engine, and not meant to handle much more. All 6.2s and 6.5s have cast-iron cranks, not forged steel like most other diesels.

In 85, a 1/2 ton C-code engine has weaker heads more prone to cracking than the 3/4 ton. The 3/4 ton J-code engine has smaller valves, leaving more metal in head for strength.

If you add a turbo, a 6.2 cannot handle any more than 10 PSI max. Block is too light/weak and compression ratio too high.

Strongest 6.2 made was in 92 when the 6.2 and 6.5 shared the same block, casting # 10149599. The most common and weakest are the earlier # 14022660 blocks with one possible exception. First year model-year 1982 blocks sometimes have better metal with more nickel in the casting.

Block numbers:
1982-1991 14022660 6.2s only
1992 - 10149599 may be either 6.2 or 6.5 as the block was produced during the
changeover from 6.2 to 6.5 by GM.

6.5 only - 12552929, 10237141, 12555506.

An 85 with those miles might be fine, but it's likely the block is already cracked. Many are cracked by 150K, and those cracks gradually get worse over time with no warnings or symptons. Then, all of a sudden, the engine blows to pieces when the crank snaps into several pieces.

My suggestion is (if you want to run a turbo). Pull the oil pan and check the main bearing webs for cracks. If not, fine. If they are cracked at all, forget it - it's a time bomb waiting to go off. If you don't find cracks, you might want to buy a stud-girdle kit that is made for 6.2s to prolong block life.

GM did not fix the crack problem until 1997 when only 6.5s were being made. They finally made the outside main-bearing bolts smaller - 12 mmm down to 10 mm to eliminate block cracking.

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