big power RB motor questions

[nyrep1]

whats the top amount of hp that people have seen from the 25 and 26 with stock bottom ends relaibly? i know that built 26's have put down 1000 + easily, and stock800 is attaniblei figure i need about 650-700 hp 500 torque (and the god of traction) to run the 1/4 times and trap speeds i am shooting for. i will spend what ever is necasery to acheive my goals, but i work every day so i want to make a smart and reliable decision, if i can make this power on a stock bottom end rb25 then i would like to but if i need to build the motor to make this power i think i spending 3500 on and rb 25 and another 2500 to3000 to build the bottom end is not smart when i can buy an rb26 for 6000 and make the power without building it. just to be clear i do know that i will not make this power with a big turbo alone, i know i will need fuel, spark, ecu head work...etc etc etc and a good deal of luck. any help for the experts will help thanks

[Joe]

the bottom end is not all you need to worry about, the rb25 transmission is limited at about 400whp

the internal limit of the rb25 is something i cant answer, i havent heard of anyone taking on 500+ hp on a stock bottom end rb25, but that dosent mean it hasnt been done.

[mark slide squad]

Not true, the RB25 trans is one of Nissans strongest transmissions. I've seen RB25 trans in Japan and Australia take excess of 750hp. Internally it is very similar to the Z32 trans, and we all know that there are plenty of Z32's making over 600whp with the same type trans. Now the RB20 trans is the weak one, its internally the same as a SR/KA type, and starts to break at around 450hp. If you compare the outside of the RB20 trans and the RB25, the 25 trans is MUCH bigger and beefier.

Mark

the bottom end is not all you need to worry about, the rb25 transmission is limited at about 400whp

the internal limit of the rb25 is something i cant answer, i havent heard of anyone taking on 500+ hp on a stock bottom end rb25, but that dosent mean it hasnt been done.

[jbanach77]

i made 424whp on a completely stock gti-r motor. that is what nissan built, i never opened up the valve cover. just a small t3t4 and 550cc injectors. and i drove that motor daily!! if a sr20 can do that i think a stock bottoom end of a rb can take more abuse that the gti-r can.

look at secret services, they have a sr20 making 530-540whp on a stock bottom end.

[JonPowell]

I heard of a guy in Australia getting 431 Wheel horsepower from a stock Rb25. Only things upgraded were the turbo and a little higher fuel pressure.

From what I understand, the transmissions are strong in the RB25 but the syncros suck. They fry after a little spirited driving.

[PROJECTRB240SX]

I WONDER HOW HARD A TURBO 350/400 CONVERSION WOULD BE.... OR EVEN A POWERGLIDE. I'M GOING TO GO AUTOMATIC WITH MY RB30DET AND I WAS GOING TO USE THE RB25DET transmission BUT I MAY END UP GOING TURBO 350 AS I CAN GET THEM FOR A DIME A DOZEN, I JUST NEED TO FIND SOMEONE TO MODIFY THE BELLHOUSING.

[cyris3d]

thres guys that allready do the turbo 350/400 swap.. ive been lookin into it for quite some time.. alot with the VL commadors.. cuz soon as my transmission blows.. the turbo 400 is goin in.. i belive there is a dood on the skylinesdownunder boad that sells adapters plates...

[Joe]

Not true, the RB25 trans is one of Nissans strongest transmissions. I've seen RB25 trans in Japan and Australia take excess of 750hp. Internally it is very similar to the Z32 trans, and we all know that there are plenty of Z32's making over 600whp with the same type trans. Now the RB20 trans is the weak one, its internally the same as a SR/KA type, and starts to break at around 450hp. If you compare the outside of the RB20 trans and the RB25, the 25 trans is MUCH bigger and beefier.

Mark

boy i mixed something up pretty bad when i read about the 25 transmission then...hmm...

[Nameless EJ6]

I've heard the 25 transmissions can take 600hp pretty easy.. and it's usually the person behind the wheel and what kind of shifting they do that determines how long it will last. Supposedly it's the synchros that don't like to last long on them.. =/ but I'm sure it would be easy to chip gears and overwork bearings with that much power.

[JeffTN]

People would crap their pants if you told that you had a powerglide/350/400 in your 240. That is if they knew what that meant.

That would be a serious 240.

[themadscientist]

The RB256 can handle in the neighborhood of 400hp on the stock shortblock, oil pump is the weakpoint. RB25 could likely do the same but it would be precarious and a drop in compression ratio would be advised for longevity. RB20 is a rock, I would expect it to handle 300 all day if the tuner knew what he was doing.

[nyrep1]

i have a freidn putting a turbo 400, sp400 in his supra right now, he is making about 550 daily and close to 700 on big bost he has been through 1 stock transmission and one built sp (i think) transmission

[Joe]

he went through a getrag 6 speed transmission?

damn those things are like bulletproof.

[nyrep1]

no not a speed it was an auto, the turbo400 is also a auto

[Joe]

ohhhhhme no domestic expert. i know about muncies thats all

ok, that makes sense then.

[Ricer Assassian]

would it be possible to modify the bellhousing on a supra, camaro, or mustang t-56 transmission and use that? i know they can handle that many horses.

[PROJECTRB240SX]

ANY BELL HOUSING CAN BE MODIFIED TO WORK IF YOU KNOW HOW TO WORK WITH ALUMINUM.

[Ricer Assassian]

working with aluminum. diffenitly not my job.

[JeffTN]

A TURBO 350/400 CONVERSION WOULD BE....

Have you thought any more about this?

[PROJECTRB240SX]

I'M TRYING TO LOCATE THE GUY WHO SELLS THE ADAPTER PLATES. IF I GET IN TOUCH WITH HIM A TURBO 400 IS GOING IN (WE ARE WRECKING A TRUCK WITH ONE HERE AT WORK).

[JeffTN]

If you could, send me the info too. :pface

I am not trying to copy you. I am just looking at different options.

[Projex240]

So why do people go through the hassle of putting in an rb25 or 26 if it is so difficult to maintain one, or to put good power down with one. Hell, if 350-400 is a breaking point, then why not just go sr....VERY good power, and less headache...not to mention more durability.Just doesnt seem worth it to me.

[PROJECTRB240SX]

I DON'T CARE IF YOU COPY ME PART FOR PART, WHATEVER GETS YOU TO WHERE YOU WANT TO BE, IS ALL I WANT TO SEE.

YEAH WHEN I FIND OUT WHO THEY ARE I'LL LET YOU KNOW AND SEE WHAT PRICING WOULD BE.

[PROJECTRB240SX]

350-400HP BREAKING POINT? HAHAHAHAHAHAHAHAHA

THE BREAKING POINT IS FAR FROM THAT! THEY CAN HANDLE UPWARDS 650HP. THE RB26 HAS BEEN KNOWN TO PUT OUT 800+ ON STOCK INTERNALS!

[JeffTN]

I have also had the C4 thrown into the mix. I am told, by a Ford buddy, that they can handle more and be built cheaper.

:shrugs:

[PROJECTRB240SX]

C4 ARE STRONG BUT ARE FICKLE. MY DAD HAD A C4 IN HIS MUSTANG AND HE HAND NOTHING BUT TROUBLE WITH IT. HE SWAPPED TO A R4 AND NEVER HAD A PROBLEM.

[JeffTN]

When I get to this step, if there is no word on an adapter plate, I might just do my own R&D. If someone else can make it, so can I. I love fabing..............or at least trying to fab.

:ylsuper

[Projex240]

Ok, thats what I was thinking. WHy go through the hassle of a totally custom project, when the max potential is so limited by a transmission. I have never headr that the rb trannys were weak, but if what someone said already was correct, then 35-400 isnt worth the money invested if you are just goin to have to replace and rebuild trannies. Not to mention that c4's and powerglides, and turbo 350-400's are not very streetable. You lose ALOT of top end with them. Thats why the only guys who run them are serious drag racers who dont car that theyve already hit their rev limiter at the 1/4 mile mark. I would maybe think of an OS giken set of gears instead. Or if you want to put big money into it. HKS makes a fully built semi-sequential transmission that uses no clutch. Its about 10,000. But then again...you guys sound serious about drag racing...so id go for it. ANother question. If you guys are so into dragging, then why not completely go rb26 and keep the AWD? that would be the best way to run good ET's

[JeffTN]

I am new to Nissans, but I would say that the RB trannies can handle anything that 90% of the swapers throw at them. I am planning on piecing together a RB setup so one thing I have to buy is a transmission. I have only seen 1 or 2 for sale and they were like $800-$1000, and thats a use one obviously. You can buy a B&M built Powerglide for Jegs for $1300 and I guarantee I would never need another one. Also, you can buy remaned 350/400/C4 from Jegs for $600 that can "repeatedly handle up to 400 horsepower with little effort."

The 350/400/C4 are very popular trannies. You can probably buy 10 for $200 at a junkyard :pface. My dad just got his C6 rebuilt with a shift kit for $400 and it was in and out in 3 days. I couldn't do that with an RB nor SR transmission if I had too.

Either way, I am not going to max out transmission anytime soon.

[fito]

I don't know where some of you guys are geting all this info. My mechanic has an RB25 puting 550HP @the wheel, it's internaly stock and it's daily driven for 3 years now. My car will make from 600 to 700hp internals stock in little over a month. In Australia this is very common. ( We all use Microtech insted of stock ECU).