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GM's bean counters strike again

The way to visually tell the difference between the forged and cast cranks is... The forged crank parting line is about 5/8th" wide and does not follow in a straight line. The cast crank has a narrow parting line about 1/8", and you can see where the parting line follows the lines of the mold used to cast the crank.
 
I suspect that the stock # on the counerweight of the crank may offer a way to tell forged from cast aside from the way of telling from the post above.

The small block chev has the 1182 foged crank and the 442 cast crank as a way to tell them apart.
 
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A little busy today putting new front tires on the tractor:WTF::eek::eek::D
 
btfarm said:
Easiest way is to hit a counterweight with a ball peen hammer.
http://www.carcraft.com/techarticles/116_0308_crankshafts_how_to/index1.html

BTW, billit is stronger than forged. But WAY more $
Click to expand...

Good stuff there. The section on crank life has me concerned. Cast crank, plus weak engine case casting material, has me really concerned that I won't see my planned 300K miles out of my '99:

Crank Life Cycle
It may seem as though a crank that passes a Magnaflux test for cracks and has had its journals reground is as good as new, but this isn't necessarily so. All metals have finite fatigue life, which basically means a crank can be loaded and unloaded a certain number of times until it breaks. How many cycles the part lasts until failure is directly related to the amount of stress or load it is under, even if that is much lower than the ultimate tensile strength of the material.

Fatigue life can be nearly indefinite if the load cycles are below a critical level, referred to as the endurance limit. What this means to us is that a thirty-year-old crank with an unknown history is a gamble in a high-performance application. If it's a steel 440 Mopar crank out of grandpa's Chrysler Newport, for instance, it may have never seen cycle loads to measurably diminish its fatigue life. On the other hand, it could have been out of cousin Bubba's nitrous'd mud-bog truck and already fatigued to the edge of failure. It's not like we're telling you something you don't already know here; if a part has already had the heck beaten out of it, chances are it's probably about to break.

As material strength increases, so generally does fatigue life and the part's endurance limit. Higher-quality cranks will last longer and take more abuse before failure--again, a no-brainer, but backed by metallurgical science. Fatigue failure generally begins to appear as minute surface cracks, which develop into fractures under repeated or fluctuating stresses. Processes such as nitriding or shot-peening put the outside surface of the metal into a compressed load, improving the surface strength and increasing fatigue life. If the engine is being built for serious horsepower or high rpm, or for use with nitrous, blowers, or in endurance racing, you may want to think seriously about crank selection. A stock cast crank may survive some heroic numbers for a few pulls on the dyno, but over the long haul, the economy of that choice may prove to be foolish savings.

All of which means that bumping fuel up and the boost up to say 14 psi means shorter life.:rolleyes5:
 
Big T said:
Good stuff there. The section on crank life has me concerned. Cast crank, plus weak engine case casting material, has me really concerned that I won't see my planned 300K miles out of my '99:

Crank Life Cycle
It may seem as though a crank that passes a Magnaflux test for cracks and has had its journals reground is as good as new, but this isn't necessarily so. All metals have finite fatigue life, which basically means a crank can be loaded and unloaded a certain number of times until it breaks. How many cycles the part lasts until failure is directly related to the amount of stress or load it is under, even if that is much lower than the ultimate tensile strength of the material.

Fatigue life can be nearly indefinite if the load cycles are below a critical level, referred to as the endurance limit. What this means to us is that a thirty-year-old crank with an unknown history is a gamble in a high-performance application. If it's a steel 440 Mopar crank out of grandpa's Chrysler Newport, for instance, it may have never seen cycle loads to measurably diminish its fatigue life. On the other hand, it could have been out of cousin Bubba's nitrous'd mud-bog truck and already fatigued to the edge of failure. It's not like we're telling you something you don't already know here; if a part has already had the heck beaten out of it, chances are it's probably about to break.

As material strength increases, so generally does fatigue life and the part's endurance limit. Higher-quality cranks will last longer and take more abuse before failure--again, a no-brainer, but backed by metallurgical science. Fatigue failure generally begins to appear as minute surface cracks, which develop into fractures under repeated or fluctuating stresses. Processes such as nitriding or shot-peening put the outside surface of the metal into a compressed load, improving the surface strength and increasing fatigue life. If the engine is being built for serious horsepower or high rpm, or for use with nitrous, blowers, or in endurance racing, you may want to think seriously about crank selection. A stock cast crank may survive some heroic numbers for a few pulls on the dyno, but over the long haul, the economy of that choice may prove to be foolish savings.

All of which means that bumping fuel up and the boost up to say 14 psi means shorter life.:rolleyes5:
Click to expand...

Yes, and all that being said, "fatigue" (as described above pretty well) IS CUMULATIVE!!

Taking a piece of metal (that is already marginal) and placing it into an application that is already taking the life out of it (more-so on a 6.5 than a 6.2), -and you surely have a recipe for trouble.

One never knows for sure how much life is left on a crank. Taking things into consideration like issues with timing (due to pop pressures being off), -or timing being too advanced, -or a balancer that isn't quite up to snuff, -and one quickly realizes that it is surely a roll of the dice when it comes to using a used crank.

The stresses inside these engines go well beyond the "gasser textbook" for sure. The stress and strain some of the parts encounter (bearings, wristpins, connecting rods, etc) begin as soon as these things are lit off, -even at idle the stresses are enormous.

It's too damn bad that SCAT won't just make us a damn forged crank and make it affordable (say in the $650-ish range).

I love my 6.5, and run the living tar out of it, -but I also realize it is a somewhat fragile engine in terms of design.

It's still running excellent, and I'm not letting it go, -not yet anyway! ;)
 
Just to add some more to the mix, Has anyone used a GEP optimiser crank in a GM block? They should be improved from the GM production units. The block and heads were upgraded with the GEP redesign.
The GEP heads can be had for around $700/pair complete. I wouldn't think a crank would be more than a pair of heads.
 
Crankme69 said:
Barry...woundn't that be about like putting lipstick on a pig :???: :) :hihi:
Click to expand...
:D:D Yes it is but some times you use what you have or can get. There will be many more military optimisers in the future. They are barely started swapping out the optimisers for the P400s
 
bk95td said:
:D:D Yes it is but some times you use what you have or can get. There will be many more military optimisers in the future. They are barely started swapping out the optimisers for the P400s
Click to expand...

Yea, like you don't have one hiding somewhere.....Waiting for a 3500HD 4X4 Crew Cab.:hihi:
 
Barry, you have more 6.5 trucks/parts/engines, than most......(Too say the least)

Have you looked at your sig latley......I can't even imagine what you got stashed away in the barn/Workshop!
 
I saw an ad on EBAY the other day just browsing it was for a 6.5 powered rollback wrecker that came with 2 additional 6.5 powered trucks for spare parts and I instantly thought of Bk95td. And that would almost be unfair marketing for him. The owner/seller must know the 6.5 market and is trying to sucker one of us with too sweet of a deal to refuse.
 
The construction company was only advertizing the 97 and 98 trucks. When the mechanic showed me this one I liked it better than the other 2 trucks. I offered $2000 less than what they were asking for them. They called me back the next day trying to get a counter offer. I stood solid on what I offered. I really wanted the truck they didn't want to sell. A 99 k3500 flatbed with plow . Less than 80,000 miles. They wouldn't sell it though.
 
schiker said:
I saw an ad on EBAY the other day just browsing it was for a 6.5 powered rollback wrecker that came with 2 additional 6.5 powered trucks for spare parts and I instantly thought of Bk95td. And that would almost be unfair marketing for him. The owner/seller must know the 6.5 market and is trying to sucker one of us with too sweet of a deal to refuse.
Click to expand...

bk95td said:
The construction company was only advertizing the 97 and 98 trucks. When the mechanic showed me this one I liked it better than the other 2 trucks. I offered $2000 less than what they were asking for them. They called me back the next day trying to get a counter offer. I stood solid on what I offered. I really wanted the truck they didn't want to sell. A 99 k3500 flatbed with plow . Less than 80,000 miles. They wouldn't sell it though.
Click to expand...



I saw the ad the flatbed (Rollback) was standard shift and without a motor......he was also offering 2 "good " motors with the "deal."
 
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