Rb25/26 Build Up

[Bronx]

Hey all, im just wondering if our sump and diff (c34 awd) is the same as the rb26 sump and diff???

im thinking of forging the bottom end rb26 i have and popping on my rb25neo head.

some things i just havent figured out yet, will the rb25 NEO head fit on the rb26 block??? i know the r33 one will fit.

i would just forge my rb25neo engine, but all i find is the r33 rb25 pistons and i dont know if they fit or not.

so its either forging the rb26 with 25 head or forging my full rb25 NEO.

anyone have any clues???

all help is greatly appreciated.

p.s i have the r33 manual, but its only got the non neo rb25 motor in it. so i cant go off that for the NEO motor

[Bronx]

i have found the piston differences between the rb25 neo and rb25 from the r33.

the r33 head works with the rb26 block while the rb25neo technically shouldnt.... i think.

the r33 rb25 pistons are close to identical to the rb26 pistons, and the rb25 neo pistons have the valve guides cut in

this is a rb25neo engine:

this is a rb25 r33 engine:

and this is rb26 enigne:

so technically does it mean that the valves would hit the piston if you were to use a r33 piston in a neo motor???

the Neo piston just seems to look like it has more meat around the sides, while the r33 ones have just a flat cut.... if that makes sense.

is that why the neo motor only has 51cc combustion chamber?

p.s just found out that the rb25 neo engine has a higher lift than the r33 one hence why the valve reliefs.

plus i think the r33 has larger valves than the NEO

i think im very very slowly answering my own questions here :S

Edited November 29, 2010 by Bronx

[dirtyRS4]

Are you looking to use RB26 internals including crank, rods and oversized pistons to get it to 2.7. RB25 and RB26 has the same bore but its the stroke that gives it the extra 100cc. Much cheaper option than a stroker kit. You will need to use a quality adaptor plate. RB26 has RB25 sump bolt pattern also. I was talking with chuckie and horrace regarding this the other day. Will make the RB30 purists mad. Eat shit. lol

Edited November 29, 2010 by dirtyRS4

[rb30dett]

You are looking to use RB26 internals including crank, rods and oversized pistons to get it to 2.7. RB25 and RB26 has the same bore but its the stroke that gives it the extra 100cc. Much cheaper option than a stroker kit. You will need to use a quality adaptor plate. RB26 has RB25 sump bolt pattern also. I was talking with chuckie and horrace regarding this the other day. Will make the RB30 purists mad. Eat shit. lol

Would be easier to forge your Neo

[dirtyRS4]

Would be easier to forge your Neo

Umm, forged with this 2.7l setup? depends on how much to spend. You gotta luv the word "easier" lol

I think the scope is to raise displacement and strenghten the engine. Funny what will fit. Gotta like nissans.

Edited November 29, 2010 by dirtyRS4

[darrinspencer]

Due to the Neo having a smaller combustion chamber of 52-56cc and a R33 Rb35 and Rb26 having approx 62-68cc, you will need to use custom made pistons to get the compression down, otherwise it will be approx 10.5:1

If you use Rb26 crank you have to use rb26 pistons due to the pin height of 30.3mm. Rb25 is 32mm.

Other wise pistons will come up too high out of the block

[rb30dett]

Umm, forged with this 2.7l setup? depends on how much to spend. You gotta luv the word "easier" lol

I think the scope is to raise displacement and strenghten the engine. Funny what will fit. Gotta like nissans.

LOL that's just it nothing will work without custom pistons stay 2.5 to get close to 2.7 would cost more than it's worth.

[dirtyRS4]

LOL that's just it nothing will work without custom pistons stay 2.5 to get close to 2.7 would cost more than it's worth.

Not more than a stroker kit and only if you dont use the RB26 crank will you run into issues. You can use RB26 pistons or there are a number of places that do custom jobbies at about the same price as forged arias or acl. I didnt say it was the easiest way to raise capacity, but it can be done. Not many ppl do 25/26 builds so it sorta narrows the options down. Each to there own i suppose.

Edited November 29, 2010 by dirtyRS4

[Bronx]

stupid NEO enigne, make life so hard. maybe i should just rebuild the rb26 head i have. might work better, but i just dont have the little attatchemtn parts for the engine, like aac valve, ignition module and vct. nor do i have cam covers

its just so dirt cheap to get pistons and rods for the rb26, i bought a set for my mate and he paid 1200 incl shipping for the full set. and i just cant find a NEO set.

p.s how the F%^$ do you change the forum layout so you dont have to click on the replies to read them!!!!!!!!!!!!!!

found out how to change it :D:D:D:D

Edited November 29, 2010 by Bronx