Seasoned Crank?
11-15-2002, 04:39 PM
#21
TECH Fanatic
Re: Seasoned Crank? Listen to J-Rod. He is saying good things here.
The major issue with any rotating or reciprocating engine part is fatigue. At 73,000 miles, the crank has turned over under power maybe 250-350 million times! Even at normal power settings, there were four firing pulses per rev, and ecah rod journal was put in compressive and tensile loading each rev.
The point is, as my old metallurgy instructor said, "Metal, like a woman, remembers EVERY time it was ever stressed, and exactly how hard." (This was well before political correctness!). There is no way for you to really tell how close this crank is to it's fatigue life limit. As long as there are no cracks, most NDI won't tell you much about when it's going to break. Only the crank knows!
There is a reason Winston Cup cranks usually only run one race. That's more like a million revs, but those are tough cycles!
If I had my choice between a new crank and a used crank (or maybe even a ...no, I'm not going there), I'd choose the new one. This would be especially true if I were enlarging the engine, making more power and driving it hard, at least 2 of which VipZ28 seems to be doing.
If you chose new, have if Magnaflux inspected anyway. It'll be good insurance, and J-Rod will be happier, too. If it flunks, take it back and get a different one from the dealer.
My $.02.
The major issue with any rotating or reciprocating engine part is fatigue. At 73,000 miles, the crank has turned over under power maybe 250-350 million times! Even at normal power settings, there were four firing pulses per rev, and ecah rod journal was put in compressive and tensile loading each rev.
The point is, as my old metallurgy instructor said, "Metal, like a woman, remembers EVERY time it was ever stressed, and exactly how hard." (This was well before political correctness!). There is no way for you to really tell how close this crank is to it's fatigue life limit. As long as there are no cracks, most NDI won't tell you much about when it's going to break. Only the crank knows!
There is a reason Winston Cup cranks usually only run one race. That's more like a million revs, but those are tough cycles!
If I had my choice between a new crank and a used crank (or maybe even a ...no, I'm not going there), I'd choose the new one. This would be especially true if I were enlarging the engine, making more power and driving it hard, at least 2 of which VipZ28 seems to be doing.
If you chose new, have if Magnaflux inspected anyway. It'll be good insurance, and J-Rod will be happier, too. If it flunks, take it back and get a different one from the dealer.
My $.02.
11-15-2002, 04:46 PM
#22
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Re: Seasoned Crank? Thanks for the info guys! I'll be picking up a new crank as well in the part list. I don't see the need for forged just yet, I won't be making THAT much power <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> (Read:My pockets aren't THAT deep!)
