I have picked up another 599 engine this one is a 6.2 that had been overhauld by a pro shop somewhere. When I first looked at it in the truck I didn't know what it was the block was yellow in color and couldn't see the numbers. But got it home torn down the number 7 crank throw is scorn really bad. My question is what about turning these cranks? Welding journals up? The rest of the crank is in good shape.

A machine shop would be the best choice for making call on weather or not the crank can be saved they know the criteria and based on undersize bearing availability they wiil determine if they can repair it.

No - that is a cast iron crank, with rolled fillets in rod and main journals to increase strength.

Grind the journals, ruin the crank...............

I have had very good luck with turning these cranks, but I won't go over .010. If you have a journal that is scored bad it won't clean up.:(

I'm gonna call the machine shop to talk with them on possible turning the crank or welding up the bad journal and then returning it down to size. I have a friend local that has had good luck with the cranks turned to a ten undersize.

Best check is to call GM, ask what over-sizes are factory available for 6.5 rod\main bearings.

Don't call a crank-grinding shop, and don't call a parts house - call GM to get factory recommendation.

Then, you can cut the crank to that depth, and get the over-size bearings anywhere.

The test, here, is - does GM offer .010, .020, .030 oversized bearings for the 6.5.

Remember - GM sells more replacement bearings than they do crankshafts, so any over-size will indicate official factory engineering position on cutting that crankshaft for possible turbo application.

GM will probably tell you not to grind the crank.

I have to disagree with both GM and GMCTD (say that 10 times fast) on this. The rolled fillets are undercut from the main journal surface. This places the critical section for stress at the bottom of the fillet with a known stress concentration factor. Since the journal surface is bigger in diameter than the controlled fillet critical section, the journal surface may be ground without affecting the strength of the crank. The fillets never have to be touched. A limit of .010 or .020 under is probably wise, but in reality, as long as you do not grind the journal surface diameter to where it is smaller than the minimum diameter under the fillet, the strength will not change. That is, unless there are grinding burns introduced by shoddy machining practice.

No - that is a cast iron crank, with rolled fillets in rod and main journals to increase strength.

Grind the journals, ruin the crank...............
Actually, I believe the term is nodular iron. Either way, I had mine Index ground 10-10 and then had it nitrided. If you think about this, .010" isn't much, and looking further, it's only .005" per side unless the index is off badly...

My crank lived through having all 3 center webs crack through to the cam bearings then the cam bearings twisted loose causing a loss of reliable pressure feed to the mains. No telling how long it was like this as it just sounded funky when I exited the freeway about 400 miles from home after running STRAIGHT THROUGH :eek:

Cast iron comes in many forms. The medium year 6.5 engine blocks (the ones that are very prone to cracking) are cast gray iron. The later ones are cast ductile iron. The crankshafts, as Kennedy rightly states, are made of cast ductile iron. Ductile iron has additional carbon added to the alloy and is processed so that spherical grains, or nodules, of carbon are interspersed in the grain sturcture of the iron itself. This gives the casting much more strength as compared to gray iron. There are also cast white iron and cast malleable iron.

For comparison:



Gray cast irona) Typical composition:C 2.5 - 4.0%

Si 1.0 - 3.0%
Mn 0.25 - 1.0%
S 0.02 - 0.25%
P 0.05 - 1.0%

b) Graphite (carbon) comes out of solution as flakes



c) Properties1) Outstanding compressive strength

2) Poor ductility
3) Excellent machinability
4) Hardness can be varied
5) Excellent damping capacity (absorb energy due to vibrations)

Ductile cast irona) Typical composition:C 3.0 - 4.0%

Si 1.8 - 2.8%
Mn 0.10 - 1.00%
S 0.03% minimum
P 0.10% minimum

b) Base iron treated with Magnesium or Rare Earth element1) Graphite comes out of solution in nodular (round) shape

2) Very low sulfurs required to produce ductile iron

c) Properties1) Good ductility

2) Machinability better than gray iron
3) Gives engineering advantages of steel and malleable iron


4) Properties can be varied by chaning matrixa) Alloying

b) Heat treating

Taken from Cast Metals Institute, Inc. "Introduction to Metalcasting" Handouts & Reference Materials.

Sealed power only lists three bearings, std, .010" over with oversized flange .25mm and .010" over with oversized flange .50mm.

Nice work, RJ.