ARC Billet Rod Broke!

BWL

BWL

Active Member
#1
#1
What do you guys think. From what you see did I totally miss something? Definitely bone stock motors are the way to go with mud motors.

[video=youtube_share;kz9XYB-N-7k]https://youtu.be/kz9XYB-N-7k[/video]
 
M

Moto Walt

Member
#2
#2
We need to call in ticycleNik1715 in here to see if this is even mathematically possible first. IF it's not mathematically possible, you didn't break a rod at all.
 
OND

OND

#3
#3
Hard to tell from the video....maybe a rod bolt backed out and then the rod broke. JMO
 
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BWL

BWL

Active Member
#4
#4
OND, that's the only thing I can figure is one of the bolts backed out. It's the only thing that makes sense.
 
KMC3420

KMC3420

Member
#5
#5
OND said:
Hard to tell from the video....maybe a rod bolt backed out and then the rod broke. JMO
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Agreed. What was your clearance between your rod and crank when mocking the motor up? I can only assume within spec, so a bolt backed out possibly and was helped along with the up/down force of the crank. These are ARP bolts which are next to none and the bolt versus aluminum, I say the bolt wins every time. The spot that the rod broke is just crazy.
 
SAS289

SAS289

Well-Known Member
#8
#8
BWL said:
OND, that's the only thing I can figure is one of the bolts backed out. It's the only thing that makes sense.
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Was there rod knock before the rod broke? You would think there would have been at least a second or two of warning before it broke.
 
BWL

BWL

Active Member
#9
#9
[MENTION=56261]SAS289[/MENTION] No knock. No warning. As a musician in a former life, I listen to everything in that motor and can tell you all the sounds it makes. I differentiate between the normal rattle of the rocker arms vs the rotation of the crankshaft. It's all different sound. There was no warning.
[MENTION=56259]Moto Walt[/MENTION] The crankshaft measured in round: Tt was only .0005 thousands out of round. Well within specs and far better than what you'd find on a Predator. The overall diameter size was perfect according to ARC specs. I could see my reflection on the crank journal and the bearings.
[MENTION=53246]KMC3420[/MENTION] Yeah, see that's what I'm thinking. It's gotta come down to the bolts. I can't figure anything out. Nothing else makes sense. Just steel vs aluminum.
 
KMC3420

KMC3420

Member
#11
#11
Are the rod thread bolts stripped? It appears maybe the bolt backed out just enough and the crank slammed the rod down or up and at that point pulled the bolt out and brought half the rod with it. I would think it would pull the rod bolt out, stripping the threads along the way, versus breaking the rod in half. :shrug:

Edit: I guess angle and thrust can do anything while at high RPM in motion. None the less, sorry for this happening to you, but thanks for sharing.
 
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SAS289

SAS289

Well-Known Member
#12
#12
Moto Walt said:
Damn... It does sound like it just backed out. I've never used or even thought about using loctite on those rod bolts either lol.
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I seen the other thread when this was brought up. I have never heard of Loctite being used on the rod bolts of any engine.
 
TheDullCarbide

TheDullCarbide

Active Member
#14
#14
The bottom bolt definitely backed out. When you look at the carnage, the top ear of the rod broke off and the bolt was still holding it to the end cap. Where's the bottom ear?...still on the rod. Why didn't that ear come off with the end cap?...because the bolt that would have held it to the end cap backed out.

You gotta save this engine. It would be downright unfair to throw away a clone with a 0.0005" tolerance on the journal just because a bolt backed out.
 
BWL

BWL

Active Member
#15
#15
[MENTION=31879]CarPlayLB[/MENTION] I simply misspoke. I torqued it to 150 inch pounds. 150 ft lbs would have broken the bolt during seating the bearing outside the motor.
 
SAS289

SAS289

Well-Known Member
#16
#16
BWL said:
[MENTION=31879]CarPlayLB[/MENTION] I simply misspoke. I torqued it to 150 inch pounds. 150 ft lbs would have broken the bolt during seating the bearing outside the motor.
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Besides that, I doubt anyone makes a half inch drive 1/4" 12 point socket to fit on the end of a 1/2" drive torque wrench. :laugh:
 
minibikin'

minibikin'

Sho-nuff
#17
#17
[MENTION=55159]BWL[/MENTION], it's not just the torque spec that's important, but also the procedure. I'm sure you followed it as you seem very competent. One thing that puzzle me is that the rod broke but didn't take out the bottom of the cylinder? Was it at idle or maybe the damage isn't visible?


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M

Moto Walt

Member
#18
#18
SAS289 said:
I seen the other thread when this was brought up. I have never heard of Loctite being used on the rod bolts of any engine.
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I loctite a lot of things on the engine, like manifold adapters and stuff ... That's what I meant. After reading it again it sounds like I loctite all rod bolts except predators.
 
trinik7597

trinik7597

Active Member
#19
#19
I know you said you torqued it on the crank outside the motor to check clearance . Then once when assembled . But what about when the cam was giving you problems did you have it apart again ?
 
minibikin'

minibikin'

Sho-nuff
#20
#20
trinik7597 said:
I know you said you torqued it on the crank outside the motor to check clearance . Then once when assembled . But what about when the cam was giving you problems did you have it apart again ?
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I was under the impression that these rod bolts were basically one time use. Not that you can't use them again, but shouldn't. Any fastener that is torqued obviously stretches and re using it can result in failure as well.


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