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Discussion Starter #1
I'm wondering, who has actually snapped a conrod here? I don't mean spun bearings or conrod bolts breaking and the big end coming apart. I mean, the actual conrod itself buckling and snapping under some extreme forces.

Anyone?
 

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im 100% sure someone has.

if you dont mind me asking...whats the point of this thread? just done a quick search and in the last month you already posted 50+ threads!
 

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Discussion Starter #4
if you don't ask, you don't learn. and in searching past threads, I wasn't able to turn up anything definitive on this one. Would like to hear a firsthand experience from someone who's snapped a rod on an RB26.

in regards to the point - well, asking obliquely yields objective answers. Although I think this is pretty straighforward!
 

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I bent one, but the piston did hit the cylinder head when the car was travelling at over 100 MPH
 

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Discussion Starter #6

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if you don't ask, you don't learn. and in searching past threads, I wasn't able to turn up anything definitive on this one. Would like to hear a firsthand experience from someone who's snapped a rod on an RB26.
fair enough:)
 

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Its far more likely the bolts would break first, the rod itself is quite sturdy, that said I have seen someone break the unbreakable... A 2JZ! if you can believe that, that was a rod bolt failure, as opposed to a rod failure as such.

I have personally broken a conrod, but not in a Skyline engine, was a Ford Cologne V6 :)
 

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You were driving it rather than mapping it though Dan, right??? :thumbsup: lol mate
Yes indeed, it wasnt a mapping project being on mechanical K-Jet and all, it was my own old XR4i, which suffered somewhat of a bottom end failure (broke a rod under the small end) following a full on burnout in the car park at college :D, weird situation, it ... failed, when I let the brake off to toodle away.... The direct result of that failure was a 3.0 Essex V6 and 'box, straight out of a Capri. Couldnt afford to do anything else!

As yet, I've broken nothing during mapping. I'm too mechanically sympathetic these days.
 

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Yep - a 4G63 with a small end failure - left the gudgeon pin in the transfer box. Virtually nothing left of the piston.
 

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have a guy on the nitrous forum that seems to bend them a lot lol





its a cavalier TD 1.7 (isuzu engine) with boost increase and 125bhp nitrous progressive, not an RB though lol but it just goes to show you can bend the rods without breaking the bolts

rod bolt failures are more likely on high revving engines
 

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Discussion Starter #15
so one RB26 rod failure that we know of so far? (bent due to bearing failure)

So what's with all the people that are afraid to push their bottom ends past 600 fly out of fear of snapping a rod? Is there any real point in upgrading conrods then in the 600-700bhp range? (beyond replacing the bolts with Tomei/ARP units)
 

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Is there any real point in upgrading conrods then in the 600-700bhp range?
Would you really want to be the one to find out the limits of the stock bottom-end? Bearing in mind (pardon the pun) that a bottom-end failure of the breakage variety at those power levels is liable to destroy just about everything. I was amused to see your comments on using standard rods, then reading in your signature that your engine is in pieces on the floor.

That said, I know first hand of a totally stock bottom-end R32 that ran 620hp for quite some time without issue.
 

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Discussion Starter #17
well, see, that's just it. I've suddenly and unexpectedly spent nearly ten grand since my engine blew two weeks ago. I could make that 15 if I went with everything completely new in the bottom end. But so far as I understand, standard cranks wobble a bit at around 7500 rpm but nothing serious, and stock conrod bolts can fail, but not the conrods themselves. So I'm making a calculated risk assessment and trying to justify forged pistons and ARP conrod bolts as being enough to support 2860-5 turbos and Poncams. A bad map will break things with det, but what I was trying to ferret out was, assuming that the engine doesn't knock, if the stock rods can more than easily take the torque and power that my engine will be making, and it appears the answer is yes.

And obviously, I DON'T want to be the guinea pig to find out what power and torque it takes to break stock conrods, even on a good tune. Which is precisely why I put up this thread in the first place - to see if anyone else had.
 

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so one RB26 rod failure that we know of so far? (bent due to bearing failure)

So what's with all the people that are afraid to push their bottom ends past 600 fly out of fear of snapping a rod? Is there any real point in upgrading conrods then in the 600-700bhp range? (beyond replacing the bolts with Tomei/ARP units)
The crank is the weak link


JUN CRANKSHAFTS AND STROKER KITS
 

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. So I'm making a calculated risk assessment and trying to justify forged pistons and ARP conrod bolts as being enough to support 2860-5 turbos and Poncams. .
if i was speccing an engine as you are at the moment i would look at buying turbos that would support the other engine and fuelling mods not running my internals at their limit to warrant turbos of a certain capability.

i certainly wouldnt spend 10 grand on an engine build and run at power levels above what people say are safe on stock rods and wait to see what happens.

not knocking you mate as you seem to like to push the boundaries, but id hate to see another 10k go up in smoke.

just my two pence worth.
 
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