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Rb25 Rod Bolt Replacement

PM-R33

By PM-R33,
in Engines & Forced Induction

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PM-R33 Grand Master

PM-R33

Posted
Posted

Hey just to clear something up. With the main weakpoint of a RB25 appearing to be the factory rod bolts failing when pushed into high power (compared to RB26 factory internals), it is not possible to put a set of aftermarket rod bolts in with the engine in the car through the sump is it? I mean it is possible to do, however it can not be done correctly right?

Had a quick search but didn't find any threads about it.

Cheers

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https://www.sau.com.au/forums/topic/293345-rb25-rod-bolt-replacement/
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Cjmartz2k Proficient

Cjmartz2k

Posted
Posted

Answering the question you asked, no, you'll need to pull the motor. Well, at least pull the head when it's time to put the piston/rod assemble back in.

And for the record, while I agree the ringlands are the weak spot on an RB25, I've seen people bend connecting rods with out hurting the piston from simply making to much hp.

PM-R33 Grand Master

PM-R33

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Posted

Ahh f**k forgot about the ringlands, very true. So you guys don't think the factory rod bolts in 25's are a weakpoint? What is the most common failure on a RB25 when pushed towards the 500+HP mark? Ringlands and rod bolts no?

Mr. Untouchable Experienced

Mr. Untouchable

Posted
Posted

before I start, i'm am not a engine builder, and this is not straight from the horses mouth, but i know of someone who was seeking advice from racepace about a 25 build and the comment was , stock 25 rods will support up to 400rwkw's, just need to bugger off the stock bolts in favour of arp gear.

but when my my tuner last tuned my car he said he stopped it at 7000 rpm, 17.6 psi (made 318rwkw) due to "rb25 rods being the weakest of rb's"

as for the weekest point in the 25, I doubt you'll get a solid answer. I have personal heard a few different answers.

The way I see it, Don't push it that hard unless your prepared to rebuild it (whenever that time comes) people laugh at me when i tell them i have made 350kw's on my stock 25. but i'm not bloody pulling the motor out unless its dead lol.

PM-R33 Grand Master

PM-R33

Posted
  • Author
Posted

Well im the same, i dont really want to build it unless it goes bang. And if i did build one, id probably do a 3L. I have heard similar things, that RB25 rods aren't that bad. They aren't as good as GTR rods, but aren't usually the main cause to engine failure unless revved hard. I also heard that replacing the stock rod bolts with ARP items helps keep them together and this was a discussion that came up regarding whether you could do it by taking the sump off as it would be a relitively cheap upgrade to aid in keeping it all together. But yeah, i didn't think it could be done. However at the time i forgot about the ringland issues with RB's and if something was going to fail that would probably be it.

How long has your stock bottom end being pushing that power for?

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