Rb25Dett R32 Gtr?

[25GTV]

Not saying I agree with putting a RB25 in a GTR but has anyone done it?

Seems like a RB26 head on a RB25DET bottom end could be a reliable and cheap option for someone who's R32 GTR may have just blown up from the oil pump issues?

Please don't flood this topic with negativity, I don't plan on doing this conversion. Im just wondering if anyone has tried it.

[KiwiRS4T]

RB30 blocks are even cheaper than RB25.

[mico]

they all have the short oil drive still...

[GTRsean]

How you gonna bolt the RB26 alloy AWD sump onto the RB25?, you'll need an adapter.

[25GTV]

Yes I guess it would be very similar to doing the rb30 conversion and would need the sump adaptor, but the rb25det is stronger and seems to last longer than the 3 litre especially at higher rpm. If they all have the same oil issues why do I rarely hear of them blowing up? Seems like every r32 left has needed at least one rebuild from oil issues.

[JonnoHR31]

the 25 isnt stronger at all, they're just generally not stressed as much as 26s. you could use a awd 25 block but i dont really see any point, if your gonna go to all the effort you might aswell just build a 30

[25GTV]

I meant the 25det s a stronger bottom end than a rb30e. Depending on the power you wouldn't have to build the 25 bottom end as its already strong enough for 250kw.

[JonnoHR31]

sorry misread, even so the 25 and 30 are both fine up to 280-300rwkw, the 30 just does the same thing at less revs

[KiwiRS4T]

I've blown up 2 RB25s which is one of the reasons I am going to RB30. I don't think there is anything esepcially strong about RB25s.

[25GTV]

Ok, so the rb30 stock bottom end is equally as strong as the rb25 stock bottom end?

[JonnoHR31]

if both are in the same condition, yes. just keep the 30 to ~7000rpm and it should live a happy life

[tm_r33]

most 30s dont have oil squiters under the pistons so highish boost on standard pistons sees them melting sometimes

30s obviously having a longer rod too doesnt help there cause at high rpm... my 30 wont be seeing 9 grand like plenty or 20s and 25s ive driven lol

[AngryRB]

most 30s dont have oil squiters under the pistons so highish boost on standard pistons sees them melting sometimes

30s obviously having a longer rod too doesnt help there cause at high rpm... my 30 wont be seeing 9 grand like plenty or 20s and 25s ive driven lol

hey i dont know much bout this topic, can you tell me , when you do the rb30/25 conversion, does that mean a limit of 6000rpm or can it be pushed to say 6500 or 7000 safely and reliably???

just wondering for future rebuild considerations with 300rwkw maximum output being absolute limit, even 280limit...

[jangles]

hey i dont know much bout this topic, can you tell me , when you do the rb30/25 conversion, does that mean a limit of 6000rpm or can it be pushed to say 6500 or 7000 safely and reliably???

just wondering for future rebuild considerations with 300rwkw maximum output being absolute limit, even 280limit...

Its a pretty loose question.. even a 300kw RB30 can be made to rev, but usually if only aiming for 300kw its just a very basic, 25/26 head on 30 bottom end, which wont be able to be pushed and revved as hard as a well built engine.

[Shane_954]

You can make 300rwkw with only 5500rpm with a 30. Thats with a dirty old single cam head.

[JonnoHR31]

hey i dont know much bout this topic, can you tell me , when you do the rb30/25 conversion, does that mean a limit of 6000rpm or can it be pushed to say 6500 or 7000 safely and reliably???

just wondering for future rebuild considerations with 300rwkw maximum output being absolute limit, even 280limit...

the less you rev it the longer it'll last in general but 7000rpm seams to be fine for most stocker bottom ends

[bubba]

If the 30 bottom end isn't built, you shouldn't really spin it above 7000rpm.

If the 30 bottom end IS built, then spin it to whatever. Good machining, good balancing, quality balancer and it should be able to spin to whatever your head gear can handle.

All this talk about 30's not revving is hogswallop.

[Beer Baron]

putting a 25 into a GTR is not a great idea. a bare 25 short motor is not much of a saving over a 26 short motor. most of the 26 value is in the head so since you'd already have the 26 head that's irrelevant. so you go and buy your 25 bottom end, assuming it's all fine you still need to buy a sump adapter ($1000 for a kit) and right there you lose any savings you may have made. you now have an engine with weaker rods, different pistons, and 100cc less capacity. GTRs are bad enough at 2.6L, taking off 100cc is not going to help.

the reason you see many more 26s failing from oil problems is they rev higher than 25s do (so more oil being pumped to the head, less in the sump) and that is combined with higher cornering and acceleration forces (from AWD). so high revs with high g-force loads mean it's very easy for a 26 in a GTR to suffer oil surge.

there is a reason no one has put a 25 into a GTR. it's a waste of time and money and no cheaper than just replacing a blown 26 with a good condition used 26.

[tm_r33]

machine, forge and balance your rb properly and u can bounce the thing off 9 grand if you like..... slap an old worn 3 litre bottom end on a turbod 25 head and rev it past 7 for any length of time and watch what the harmonics of the thing do to it.... rattle rattle ratlle RATTLE RATTLE RATLE knock knock knock KNOCK KNOCK..... oh thats strange.... i have f**ked bearings and journals.... my rods dont seem straight and it appears someone took to the top of my piston crowns with oxy acetaline......

after saying this i bet there is some one on here who steps up and tells me they have a 250 000 km rb30 bottom on a 25 head with about 2 bar being shoved down its throat that is still running lol.

there are just so many factors that come into it... ive seen bog stock rb25det put a rod through the block with only about 100 000 km on it... some times shit just fails.... and some times i dont know how it lasts lol

[mico]

rips nz ran a 7 with a std rb30 bottom end.