Broken Crankshaft Count?

Please pick the one that you had break


  • Total voters
    185

Ne-max

I like turtles
Nov 15, 2011
3,361
64
48
Lincoln, Ne
How could it be unless it was already cracked

Do you think it gets weaker and weaker before it cracks or do they just up and crack? I personally would think that having so much stress up to that point will still leave a weak spot in it. But I might be thinking to much
 

S Phinney

Active member
Aug 15, 2008
4,008
18
28
Quncy, Fl
It really depends on the material traits. Some weekend until failure and some just fail. Take 4032 and 2618 aluminum used in pistons. 2618 will take more abuse. While 4032 initially appears better but suddenly fails without any signs of failing.
 

countrycorey

Trust Me I'm an Engineer
Jan 30, 2010
1,512
35
48
LA
Do you think it gets weaker and weaker before it cracks or do they just up and crack? I personally would think that having so much stress up to that point will still leave a weak spot in it. But I might be thinking to much


Yes, it gets weaker due to fatigue


Corey
 

zf>allison

you never had your car.
Apr 30, 2013
3,394
0
36
elsberry mo
Do you think it gets weaker and weaker before it cracks or do they just up and crack? I personally would think that having so much stress up to that point will still leave a weak spot in it. But I might be thinking to much

My thoughts were it would fatigue that's why some brake as there cruising down the road. Not at a max load situation.
 

Dave c

New member
Jul 7, 2013
294
0
0
I too have heard of alter fire crank failures. It does seem to be much less often than standard fire. However I know the alter fire spools slower and makes less power with a direct swap.
 

LBZ

Super Moderator
Staff member
Jul 2, 2007
9,905
151
63
46
B.C.
How could it be unless it was already cracked

My thoughts exactly.

Already being harmonically cycled, shock loaded, etc. "X" amount of times with the standard FO which would stress and add fatigue to it would be my guess as it maybe being factor.

And those that didn't properly check or maybe didn't check it all may miss cracks just starting. Brian found a crank like this-good thing he had it properly checked.

For best results, I would suggest starting new myself.
 

Ne-max

I like turtles
Nov 15, 2011
3,361
64
48
Lincoln, Ne
Already being harmonically cycled, shock loaded, etc. "X" amount of times with the standard FO which would stress and add fatigue to it would be my guess as it maybe being factor.

And those that didn't properly check or maybe didn't check it all may miss cracks just starting. Brian found a crank like this-good thing he had it properly checked.

For best results, I would suggest starting new myself.

This is the reason I am putting a new LB7 in my build.
 

LBZ

Super Moderator
Staff member
Jul 2, 2007
9,905
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B.C.
I too have heard of alter fire crank failures. It does seem to be much less often than standard fire. However I know the alter fire spools slower and makes less power with a direct swap.

Another "I heard of" story.

Got any proof Wade?
 

LBZ

Super Moderator
Staff member
Jul 2, 2007
9,905
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B.C.
I looked into a LML. But already had a LB7 dampener and flexplate to use on it. Could now find any info on what style a guy needed for a LML crank.

From what I understand LBZ up will work. I'll find out soon enough. JD Dave did it with LMM stuff IIRC.
 

56taskforce

Well-known member
Mar 30, 2014
1,081
56
48
So if you take all 8 cylinders and have a single combustion event in each, or in other words a full cycle, does the timing vary a total of 8 degrees if comparing 2 cylinders? If that is true and then you combine the info on non equal cylinder charge according to Banks, would this be a good indicator of why the cranks, regardless of either stock or billet aftermarket break in the same place more often than not? Just trying to wrap my head around this.

It is a four cycle meaning each cylinder fires every 720° of rotation devided by 8 cylinders that is 90° between power cycles.