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On 31/08/2026 at 06:16, kpr said:

Is up and running again on the og bottom end

So internet scientists,  what broke first the rod bolt or the cap?

 

Some one suggested the cap broke first,  hence why the end of the rod bolt is bent.  which makes sense, as would have peeled the remaining cap off    the cap is broken through the weak point where its been machined for the bolt and there is a sharp edge

Going against that theory.  the angle of the break in the bolt suggests the bend in the bolt is the wrong direction, as per bottom picture.   this is assuming what's left in the rod didn't spin around after the fact.    
The big dent in the head of the bolt and the flat spot on inside just below the bend, suggest was plausible the bend happened after the bolt broke 

 

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I'm not an expert but I sat through material science 101 at some point, I think the rod broke, then the bolt, and then the cap. What was left of the rod swinging around the crank, windowed the block, and in doing so, hit the rod bolt, bending and then breaking it (that could also explain the dent on the side of the bolt head), then the cap let go at the end because it was only held on by one bolt.. 

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Posted

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the cap is suspicious cos with all these maxpeeding rods (and all the others that look exactly the same) the have this cut which feels like a stress multiplier.

i dunno what breaking the cap first would do though, would it eventually just break off and flyaround leaving the rod and piston just stuck further up the hole rather than tearing the rod in half?

Posted

Seeing how the other 3 rods/bolts/caps came within a fraction of doing the same. Any clues to be had by examining those? 

Maybe crack test or xray the rod / cap / bolt? 

I will chip in some bucks to see that. Could be real interesting.

Or not. Just dont know.

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Posted

Am also not a fan of the sharp cutout around the rod bolts. is a weak point for sure. 

Looks like the rod has been jammed up against the  bottom of the bore once the cap/bolt broke.  you can the heat marks in the side of the rod where the crank has started to saw it in half. then i assume crank grabbed hold of it and chucked it out the side. so yeah all that damage happened after was already broken 

20260827_113738a.thumb.jpg.8211a8b2a41f007b679670093e42425c.jpg

 

I haven't looked closely at the other rods yet.  maybe tomorrow 

 

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Posted

Are we sure it's not piston stuck in the bore then crank tore the rod apart? Probably not, but could be.

I suppose you could test the failure point for the rods. At ~9k rpm there's about 2.5 tons of force on the downward swing of the rod. So pop a bar through the little end and suspend a female Indian elephant from the other, then see what gives way first.

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Posted

The top side of the piston,  rings,  bore, all look nice, other than aftermath damage . so unlikely was a piston or clearance issue.  

 

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Posted
On 03/09/2026 at 02:46, BiTurbo228 said:

Are we sure it's not piston stuck in the bore then crank tore the rod apart? Probably not, but could be.

I suppose you could test the failure point for the rods. At ~9k rpm there's about 2.5 tons of force on the downward swing of the rod. So pop a bar through the little end and suspend a female Indian elephant from the other, then see what gives way first.

Could swap the female Indian elephant for deep fry? That window licker would weight similar amounts

@kpr

Posted

What needs to be appreciated here is the sheer number of hours that has been put into this - seriously impressive.

Fingers crossed this reveals some extra HP!

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Posted
4 hours ago, kpr said:

Cant polish this turd no more.   so just throwing shit against a wall at this point 

Time to upgrade to a 20v ? 

/I'll let myself out 

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