Look at the pictures again, it wasn't a cylinder failure.
Pistons, sleeves, ROD BEARINGS, AND MAIN BEARINGS were perfectly fine.
Pistons, sleeves, ROD BEARINGS, AND MAIN BEARINGS were perfectly fine.
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NSX Crank Failure - stock bottom end
- Thread starter stuntman
- Start date
Yep I saw that I was just curious which cylinder the counterweight failure was closet to. I assummed hopeflully not incorrectly that counterweight was closest to a particular cylinder, I see that the main journal is in fine condition, just wondering?
When I was reviewing the photo I noticed it was not at the flywheel end but on the dampener end and the counterweight failure seems unusual. Just my natural curiosity with rotating apparatus.
When I was reviewing the photo I noticed it was not at the flywheel end but on the dampener end and the counterweight failure seems unusual. Just my natural curiosity with rotating apparatus.
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If you live in a big city with a large university, I would take it into their metallurgy department and see if they will take a look at the break. They will be able to tell you whether it had a pre-existing defect. Or you could walk into a commercial metalurgy lab, they might just look at it for free. I have taken a course but I can't remember to tell you what to look for. Personally I highly doubt a defect. You were running boost right? Remember Honda produced a special crank for the original low torque 440hp spice engines. With due respect to the great work Chris and of course Shad are doing: Splayed crank with high torque = drastically reduced life span. Not that thats a bad thing, I just think we are kidding ourselves thinking this crank is good for more than say 350 ft lbs of torque. And i think we are giving a lot of new owners the wrong impression that when they spend 15k on an engine it will have a long life, when in reality they need to figure 15k every few years. It's just too bad we can't get these cranks produced cheaper. We really need to have a spare short block laying around. I can't imagine the feeling of turning the boost knob(figuratively) and then hearing a 20k clunk. If you were not running the stock damper, search on that, it's been an issue. It isn't partially broken is it?
freak failure, I have to believe that. dont waste money on a forged crank just make sure it is balanced. the tell it was bad had to be noticible.....any gut that something was off?
david
david
I'm going with a billet crank due to it's larger rod bearings.
The consensus seems to agree on a casting flaw, not an imbalance issue.
i would have hoped that with a built engine the crank had been x-rayed/fluxed to verify. then again, if the part came off the production line anything is possible.
It was an OEM motor built by Honda...
i know but wasn't it blueprinted by factory?
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Hi Stuntman--
I never did see an answer to the question of whether you had a lightweight crank pulley or if you had the oem or any other harmonic damper installed. Just curious.
I never did see an answer to the question of whether you had a lightweight crank pulley or if you had the oem or any other harmonic damper installed. Just curious.
Everything was stock. Motor, pully, harmonic balancer, etc...
I've seen failures on stepper motor shafts from having the drive belt too tight which puts a side load on the shaft eventually snapping it of as it rotates. You would certainly get rotationally induced fatigue if the crank was somehow getting stress perpendicular to the rotational axis (rather than around the axis where the rod force would go). But it seems that would likely result in it being unbalanced as well.
I didn't read most of this post cause I am work at this time but I did wanna add my .02 , from what I have senen at our dealership when this has happened is another shop putting to much tension on the crank pulley, now I know you know your stuff but this could have been the problem, now that its apart it will be hard to tell but any bent or cracked cranks I have seen have always been related to this.
as everyone else has stated be glad it didn't take out anything else, get another crank have it line bored and go back to enjoying her.
as everyone else has stated be glad it didn't take out anything else, get another crank have it line bored and go back to enjoying her.
This was exactly the point I was trying to get across with my questions from my post but this was not the direction my comments were taken as. I have years of experience with servo motor, spindle motor rotational bending moment failures and the root cause has predominately been an outside influence on the design. I'm not saying this is the case here but I was interested in which cylinder this failure happened to take a look at how this may have or may not have contributed to the failure mode, purely natural curiosity on my part.
Main bearing #1 barely went though the 1st layer, it was in great shape for what happened.
I know you said everything was stock; what about the clutch was the clutch stock too?
I know 2jz, and F20c's have an issue with crank walk (where the thrust washers drop into the oil pan the crank shaft will shift back and forth) and it usually comes from a heavy clutch.
I've seen a lot of cranks fail (various makes and models; but mainly commercial trucks) and when they fail they all fail the same way. As in it looks like it got sheered with a saw. On commercial trucks it seems the failure is due to work. Like the trucks have been waaaaay over worked.
Carrying loads that are way over it's limit etc.
I know 2jz, and F20c's have an issue with crank walk (where the thrust washers drop into the oil pan the crank shaft will shift back and forth) and it usually comes from a heavy clutch.
I've seen a lot of cranks fail (various makes and models; but mainly commercial trucks) and when they fail they all fail the same way. As in it looks like it got sheered with a saw. On commercial trucks it seems the failure is due to work. Like the trucks have been waaaaay over worked.
Carrying loads that are way over it's limit etc.
I'm new to NSX's, but I've been around the DSM scene for a long time. A lot of our guys are making 600+whp on stock cranks(me included) with only the occasional crank fracture like this one. It's definitely not anything like a tight alternator belt, but the ones I've seen with ours tended to just be fatigue or an 11k rpm over-rev. I'm going to guess Acura built just as good or a better crank for these, but occasionally one will break. It's good to see you caught it in time, it could have been much wor$e.
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- 19 February 2008
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Crazy...
Go ahead and bring that by the shop Billy,
I'll have that thing Tig'd up in no time and have you back on the track once again!!
Go ahead and bring that by the shop Billy,
I'll have that thing Tig'd up in no time and have you back on the track once again!!
