neo rb25det bottom end replacement

[braden]

hey guys i was wondering if anyone knew the bore specs for the 26 pistons vs 25? I have a rb25det(neo) with low compression in clylinder 5&6 both around the 80psi mark, so i have the block completely disassembled and going to be getting it honed and cleaned up. I have a buddy with an extra set of amazing condition r32 gtr pistons connecting rods wrist pins etc. i was wondering if anyone knew if i was able to run the pistons and rods with my stock neo 25 bore? i would be running them DD for probably a year till i rip my motor apart and upgarde to tomei.

thanks guy's.
Braden

[DreadedFist]

Pretty sure the gtr crank, rods and pistons will swap into a 25 block. Don't know about JUST the rods and pistons, though, as the rb26 has a longer stroke.

[Skym]

The big end on conrod is the area you have to worry about. It's bigger on RB26, RB25 conrods vs RB20 that has smaller bigend.

I think you would need RB26 crank, RB26 conrods, RB26 pistons (balanced), Tomei 1.2mm metal headgasket, ARP headstuds, Nissan repair gasket kit, etc.

[braden]

i have apexi metal headgasket, oem full gasket rebuild kit, acl race bearing's right meow! but i still need to collect more parts.

[BenC]

The 25 and 26 rods are the same length, I believe the 26 rods are a bit beefier though. The 26 pistons are shorter to accommodate the larger stroke on the crank

[braden]

alright so i have to find a crank ...lol shitty

[RB30DET]

I have an article from the Australian publication 'High Performance Imports' from about 3 years ago that discuss about the different combination / strokes that can be achieved (RB21, 22, 23, 24, 27, 28, 30, 31, 32 and 33) by combining different parts from various RB engines. An example is, I used a RB30ET block (from a Aust-spec R31) and the original RB25DET head from my 1997 GTS25T to build my hybrid RB30DET which puts down 585hp at the rear wheels, this is much cheaper than spending a 5-figure sum on a OS-Giken RB30 conversion. Why the 3-litre ? well, anybody that's tried to spool up a big turbo such as a GT35R or a T04Z with a RB25 or 26 would tell you that there's a bit of lag, to give you an example, my Garrett GT35R turbo (0.82 rear) used to come on full boost at around 4500rpm, but that figure dropped to 3500rpm by going to the 3 litre bottom end and a 1.06 rear housing on the turbo....HUGE difference. The only thing I would have done differently is instead of doing the solid lifter conversion with my R33 RB25DET head, I should have simply used a NEO RB25 head which has the solid lifters in place already.
Back to your question, as Ben said, the rods are identical in the RB25 and 26, however, its the crank and pistons that are slightly different, so if you want to use the '26 pistons, the crank will be required.
When you're ready to make some serious power, if you want, let me know and we could see if we could get a RB30 bottom end out your way - I have 4 complete bottom ends sitting in the shed from wrecking various R31s. Then you would probably be the only person in your country with that set up - the RB30 was available only in Australia, New Zealand and Africa.

[BenC]

There's a few 30's running around here. I Probably should have went that route but it's a bit of a headache from what I've read

[braden]

thank's alot guy's yes i have sourced a 26 crank so if anyone wants my neo 25 crank throw me an offer,also have the rods and pistons,but cylinder 5 & 6 have low comp and need to have rings replaced, thanks alot guys!