my experiences with rb's, lots of info

[240z!!!]

as many i have been fighting with my rb25 for some time and i have lots of information that may be beneficial to others,

i use top hat mounts(never had a problem with them i would suggest getting the poly instead of rubber mount though).

i had issues when i first got my 25 with breaking the alternator/water pump belt(due to the fact that the previous owner lost the spacer for the bottom of the alternator) but it ended up overheating and warping the head slightly so i went with the full cometic street headgasket kit and never had a problem out of any of there gaskets daily driven and slightly got on for over a year(of coarse the head must be decked or a metal headgasket won't seal properly 9x out of 10.

rb coilpacks are perfect how they come and you should not need to upgrade them unless you have faulty coilpack, i upgraded mine by following myths and ended up wasting a good amount of money, i seen no gain

the usdm part number for the oem vtc sensor is 23796-97E08 and they come from the maxima with the ve30de(there are 2 vtc sensors on a maxima, one per head as i pulled muliple sets from the junkyard) i believe i paid a little over $100 for it brand new from nissan

usdm part number for oem injector seals to plenum are 16636-72POO( i believe i paid a little over $2 a piece for them (be careful as i checked with 4 nissans in my area and they all had different pricing)

for rb25 owners, im running a z32 ecu that is nistuned, contrary to popular believes im using the later 16bit ecu instead of the early 8bit and i have no problems what so ever and still retain the vtc, the wiring process is very easy which most of it is depinning wires and repinning them. and if you are deleting the vtc you can use the rb20 ecu nistuned and thats the only function you lose.

the hitachi and mitsubishi cas's found on rb20's and rb25's are interchangable, now the only difference between the rb's cas and j30's/300zx is that the position of the trigger wheel vs. the position of the keyway is slightly different(to be exactly it's 1.5 cylinders off in position, so if a j30's cas was bolted to an rb25 then it would fire whenever number 2 cylinder in the sequence is halfway down, i attempted to repin my firing order(so if my order is 123456 i repined it to 612345) and it ran the car but with the cas all the way advanced, so i then broke the keyway out of the j30 cas and positoned it so that number one cylinder fired exactly where it is suppost to(not easy but very doable) so there is a usdm replacement for cas's

what ive ben attempting to do lately is do a full rb26 valvetrain coversion on a rb25 head, this is doable with a good machinist, first the rb25 and rb26's intake/exhaust flanges are different, second they have the same cc chamber size so a rb26 head could be retro fitted to a rb25 if you delete the vtc, drill and tap the block to accept the 12mm headbolts (instead of the 10mm headbolts a rb25 uses) and get the itb setup and twin setup from a 26 ( or any manifolds that fit a rb26 because the 25 manifolds will not work)
so to make everything i have work i was just going to swap the valvetrain, you must have everything from the rb26 head including cams, the intake valves on a rb26 are slightly larger so cutting the new valves in is required, and the rb26 valves are slightly longer due to solid lifter setup, if you keep that in mind it can be swapped, i wish i could have finished mine but im just upgrading to a rb26 so im just gonna get rid of all my head parts

lastly my final adventure is im working on a r32 with the rb20 into it and were gonna swap a rb25 into it were gonna use the 20 trans due to cost for now, and were going to use the rb20 harness modified due to the rb25 previously being installed into a s13( it can be done, and its much easier than most think)

but for now this is a little of my story with rb's my fingers hurt and there are things im forgetting and will post them when i can remember and if you have any questions ill be happy to help if i can

[StricNyne]

lol, i am adventerous but i think its easier to just buy a rb26, most people that want to convert head dont really know why, or make enough power to need it (honetstly cams is the issue with rb25 and thats really it, but stock cams work until around 500hp without an issue unless u wanna move powerband, or rev past hydro lifter limits) knowing what i know now, i woulda just saved up, and did a stock rb26 swap a long time ago, i would of made my 350 power goal, had solid lifters, itb, and done it for cheaper than buying my rb25, and upgrading exh mani, turbo, inj, and everything else i did to mine. although 26 prices got a tad high recently. some good info in there though!

[Cjmartz2k]

lol, i am adventerous but i think its easier to just buy a rb26, most people that want to convert head dont really know why, or make enough power to need it (honetstly cams is the issue with rb25 and thats really it, but stock cams work until around 500hp without an issue unless u wanna move powerband, or rev past hydro lifter limits)

Couldn't agree more. This coming from somebody who ran an RB26 intake/ITB's on an RB25.


Lots of good info in there though. I also agree about the stock coil packs. They are more than enough for whatever 99% of people can throw at them if they are working properly. Problem is many times they are not. If you have ready access to all the cheap replacements you could want, it makes no sense buying "upgrade" coil packs. I get a kick out of seeing stock turbined RB20 guys buying $700 worth of split fires over here when the junk yards are overflowing with perfectly good factory pieces for next to nothing.

Good info on the Z32 ecu. It's a really good/cheap alternative to some of the aftermarket ECU's out there

[racebreads13]

i have a rb25 in my s13 also and it runs good but lately i been thinkin i should just sell the swap except the transmission and mounts and go rb26 because i wanna be at 350 also..

ebay mounts work perfect and save alot of change...

[Cjmartz2k]

i have a rb25 in my s13 also and it runs good but lately i been thinkin i should just sell the swap except the transmission and mounts and go rb26 because i wanna be at 350 also..

Are you being sarcastic or serious? I really can't tell, sorry

[racebreads13]

im being serious... the turbos on the rb26 will hold up to 350 reliably right??? and cjmartz2k do u live in okinawa currently???

[flatrate]

good info on the vtc solenoid, mine is leaking out of the connector

Inform me, why do we have to drill out the threads in the block to fit an RB26 head? just use the smaller head studs and make sure the dowels fit properly... its only a couple mm

or perhaps have a stud make to be 10 on one side and 12 on the other.... drilling and tapping head bolt holes is a PITA

what am i missing here?

[240z!!!]

^ i tend to do things right with my car sure you could throw in 10mm bolts when its support to have 12mm, but im for reliability and if its questionable i wont do it...and a 12mm bolt with one 10mm end wouldnt be that bad of an idea but it would probably cost an arm and a leg to find ones with the tensile strength you need and the proper size most likely will be custom, so if they go bad you have to have new ones made, plus how reliable will that be under high horsepower?

but drilling and tapping headbolts isnt that bad considering we have rb's with iron blocks(not aluminum) and you could do it yourself for free if you have the tools

[Cjmartz2k]

im being serious... the turbos on the rb26 will hold up to 350 reliably right??? and cjmartz2k do u live in okinawa currently???

Yup, I live in Okinawa.

The stock turbo's on a RB26 can support 350hp IIRC, but thats certainly no reason to do a motor swap. Just change the turbo on what you have in there now. You can make 500rwhp on a stock unopened RB25 with the right turbo and supporting mods. You can get well above 350hp even on a stock RB20 with a different turbo and supporting mods for that matter.

[flatrate]

im sure it could be done and be reliable as long as there are proper fitting dowel pins the head isnt going to shift, the bolts simply hold it down.. so what there a little smaller, holds the 25 head just fine...

someone do it... haha

[240z!!!]

the only real problem i see with using rb25 head studs is the 2mm gap is going to take the load on the washer which will crush in under 80 ft lbs. (since arps will most likely be used) and you may have uneven toque specs if not as soon as you do it then maybe down the road, although you could double up on the arp washers

[racebreads13]

im being serious... the turbos on the rb26 will hold up to 350 reliably right??? and cjmartz2k do u live in okinawa currently???

Yup, I live in Okinawa.

The stock turbo's on a RB26 can support 350hp IIRC, but thats certainly no reason to do a motor swap. Just change the turbo on what you have in there now. You can make 500rwhp on a stock unopened RB25 with the right turbo and supporting mods. You can get well above 350hp even on a stock RB20 with a different turbo and supporting mods for that matter.

I bet its amazing!!! i want to go check ebisu out asap! anyways well i was thinking of a turbo upgrade most likly a GT3076 garrett i found one this gut i know used on his sr for a little bit and is now wanting to see for $800 but idk i mean i have a power fc and z32 mafs all id need is injectors, lil moe boost and a tune then safe 350whp right??

[240z!!!]

with the right turbo you can make 350 with a tune, ive seen the stock injectors make it past 380hp , of coarse you have to run an extra inline 255 walbro fuel pump, have a good reliable fuel pressure regulator, and up the fuel pressure a hair...of coarse those are mods needed to make higher horsepower anyway.

[240z!!!]

lol, i am adventerous but i think its easier to just buy a rb26, most people that want to convert head dont really know why, or make enough power to need it (honetstly cams is the issue with rb25 and thats really it, but stock cams work until around 500hp without an issue unless u wanna move powerband, or rev past hydro lifter limits) knowing what i know now, i woulda just saved up, and did a stock rb26 swap a long time ago, i would of made my 350 power goal, had solid lifters, itb, and done it for cheaper than buying my rb25, and upgrading exh mani, turbo, inj, and everything else i did to mine. although 26 prices got a tad high recently. some good info in there though!

the only reason i wanted to do the head conversion is i found a rb26 head for $400 bucks complete from a r33, i originally went with the rb25 because i got the thing together as a whole with mounts, driveshaft, wiring done, ect so i went for the 25 knowing i was gonna go 26 and keep the transmision, the crank pulley, the powersteering pump, the driveshaft, the mounts ect. so i have everything to do a 26 and have more than enough experience necessary with rb's to do it right.

but its funny you should say that because at this time i am selling my rb25 and buying a rb26