Rb26 Head On A Rb25 Block

[dori34]

tried searching but nothing came up, only got results from RB25/30 & 26/30 conversions

would a RB26 head fit on a RB25 Neo block? If so/if not, what is different and what mods are needed for it to fit?

Im sure some guru on this forum would have tried this or know if it will/won't work.

any help much appreciated

cheers

[GTScotT]

im no guru, but theres no way its not possible. afaik it would be a straight swap, yet obviously the accesories to match the manifolds etc would need to be changed.. but the head itself should and will bolt on.

as a simple reference to this sort of thing, what i normally do is look at what youve already listed above... you know 25 heads go on 30s, you know 26 heads go on 30s... reference the two and decide for yourself.

obviously you may have some sort of issue with an oil gallery for the VCT hope ive shon light on the right path for you

[R31Nismoid]

Why would you not use the NEO head? The NEO head, done right, is better than the RB26 one.

[Kaido_RR]

yes it fits, if i remember right you just need to tap out the head stud holes in the block as the 26 head use larger ones than the rb25 (or it could be the other way around)

personally i think rb26 head is far better than the rb25

[GTScotT]

Why would you not use the NEO head? The NEO head, done right, is better than the RB26 one.

Elaborate?

[R31Nismoid]

You have VCT, solid lifters etc etc. Just put a RB26 throttle body setup on it and you are laughing.

Anyone that says a RB26 head is superior to a NEO head is crazy.

Done right a NEO25/26 would be better than a 26. VCT is WIN for a super performing streeter.

There are a few NEO25/26's floating around that i know of funnily enough as well... not common, but will gain popularity over time

[Kaido_RR]

You have VCT, solid lifters etc etc. Just put a RB26 throttle body setup on it and you are laughing.

Anyone that says a RB26 head is superior to a NEO head is crazy.

Done right a NEO25/26 would be better than a 26. VCT is WIN for a super performing streeter.

There are a few NEO25/26's floating around that i know of funnily enough as well... not common, but will gain popularity over time

for what it cost to do the rb26 plenum swap, he is better off just using a 26 head. and i would know as i have done the plenum swap.

i was always under the impression that the 26 was superior and it flow and shit load better than the 25 head

[dori34]

thanks for all the input fellas. kaido is right, it is cheaper to put the whole head on rather then get the adapters made to just fit the plenums.

[FineLine]

for what it cost to do the rb26 plenum swap, he is better off just using a 26 head. and i would know as i have done the plenum swap.

i was always under the impression that the 26 was superior and it flow and shit load better than the 25 head

They are identical.The only difference is in the bolt patterns for the manifolds, the vct, and in the case of the 33 head hydraulic lifters.

You would be surprised at how little difference there is between a 25 and a 26 long engine. The engine blocks are the same with the 26 having one extra oil return hole for the second turbo. Crank is slightly different for the extra 60 odd cc capacity.

If you think about it it was just good business sense on nissans part to utilise what they already had in inventory.

Even the 25 box is simply a gtr box minus the transfer gear.

The conspiratorial side of me suspects the only reason they made the few slight changes was to stop precious GEETEEAAAAARRR owners whinging in much the same way the GT falcon boys whinge about the XR6 being a tougher car.

[R31Nismoid]

^ Agreed on all points.

I still to this day wonder why the RB26, Gen3 from the R34, did not get VCT.

It would have been rather easy to do considering it was already done with a NEO, and would have made it the king of kings!

Getting RB26 TBs/plenum onto a NEO head is not a major or costly task when you consider you sell off the NEO intake and so on.

Also NEO heads seem to be cheaper because people think "RB26" is the be all and end all.

You'd be lucky if it was $400 more. For VCT, i think $400 is more than worth it, probably one of the best bang for buck advantages you can get.

[dori34]

you are making me think twice about this R31Nismoid.

perhaps i should go down the greddy plenum path instead?

changing to RB26 head was the first thing i had on my mind as it would make things alot easier when i go the DETT path.

[GTScotT]

Nismoid........ you are going to make me cry.......... after finding my ecu was blown i was considering ditching VCT for an R32 ecu for cheaper/easier tuning..

its a whole new can of worms for me now... ill have to compare VCT setups to non VCT camed setups and go from there.. probably a relevant study to that of the neo vs 26 head.. alot of cams i see say non VCT where as others dont specify, and that doesnt necessarily give me confidence to think they will be effective with VCT.

big, BIG can of worms...

[dori34]

i guess if you have standard cams or using step 1, it would be good to have vct/neo. but if you are going step 2 or bigger then it won't be needed so won't make a difference anyway

[R31Nismoid]

you are making me think twice about this R31Nismoid.

perhaps i should go down the greddy plenum path instead?

changing to RB26 head was the first thing i had on my mind as it would make things alot easier when i go the DETT path.

Ah see here in lies the issue... you want the RB26 ITB's of the + the VCT.

Not having the ITB's would not be doing the effort any justice

Why wouldn't you just put a single on? Much simpler. But then adaptor plates aren't overtly hard to create if you wanted a TT setup.

You are NSW so you don't have the issues with big singles like Victorians do, so i would go the easier single option

Nismoid........ you are going to make me cry.......... after finding my ecu was blown i was considering ditching VCT for an R32 ecu for cheaper/easier tuning..

its a whole new can of worms for me now... ill have to compare VCT setups to non VCT camed setups and go from there.. probably a relevant study to that of the neo vs 26 head.. alot of cams i see say non VCT where as others dont specify, and that doesnt necessarily give me confidence to think they will be effective with VCT.

big, BIG can of worms...

Well even just run of the mill RB25 (R33's) results that are floating around here show you without the VCT, the results are not as good.

Do you even need cams?

Guilt-Toy, myself and a few others have all cracked over 350rwkw with factory RB25 cams and response/results as good as anyone else that would spend 4 figures on a set of cams and so on.

There is a lot to be said for factory cams that is not proven on a dyno sheet. Where the smaller OEM stuff shines is on the street - on/off boost transition and so on.

I don't have VCT on my 26 head obviously, but with the factory cams and so on, it's just punchy everywhere even from 2500rpm.

I can burn around in 5th @ 60km/h without a drama. Im not so sure larger cams would let the car perform like that, which for a street car would simply piss me off.

Should one week work go sour and i get some super dooper unexpected overtime, V-Cam could be on the menu...

Of course there is always a counter argument, and rightly so. It does make the world interesting

Gowever from what i have seen personally from friends who've had cams, gone back to factory and so on.

And also the advice given by Racepace, OEM cams are the way!

[dori34]

Ah see here in lies the issue... you want the RB26 ITB's of the + the VCT.

Not having the ITB's would not be doing the effort any justice

Why wouldn't you just put a single on? Much simpler. But then adaptor plates aren't overtly hard to create if you wanted a TT setup.

You are NSW so you don't have the issues with big singles like Victorians do, so i would go the easier single option

i like this idea because it is something differnet.

ive been speaking to jeffworld2 who has done this on his r33. he said its fquite responsive so i will have to go for a test drive in his car to see how it feels.

then i will compare it with a test run in a rb25 with 3076R (the turbo i would go if i was doing a single).

the twin turbo growl and exhaust note is awesome. sounds like a gtr lol

eg:

[T-Rex]

VCT is just a complicated way of saying "harder power". In general more boost and more fuel equals more power and more performance. Adding variables just adds complications.

Now this is a question not a statement, whats your thoughts on making 1400hp out of a RB26 head without porting?

[D_Stirls]

There are advantages of the NEO head that have been mentioned above, one of the limitations is that you are limited to 9.25mm of lift with your cams due to at exposing of a gallery if you go any higher.

[dori34]

also got another question, as stated above the 26 head will bolt up to the 25 block so now i can assume

that a rb25 head can bolt straight up to a rb26 block ? of course i will need to modify the sump for rwd configuration.

any help much appreciated.

cheers

[lachlanw]

this thread made my day . i already knew everything that was in it but its nice to hear it again . also the neo head has 1mm larger exhaust valves than a 26 head . and they are f**king cheap last week saw a complete neo head with nothing wrong with it go for $280 NZ. can wait to build my 26neo

[PM-R33]

VCT is just a complicated way of saying "harder power". In general more boost and more fuel equals more power and more performance. Adding variables just adds complications.

Now this is a question not a statement, whats your thoughts on making 1400hp out of a RB26 head without porting?

Harder power? Do you even understand the advantages of the VCT? It is to make good low down power for a street car that 99% of its time is starting and stopping and therefore in a rev range of 1000-4000rpm. Most setups aren't making peak boost up until the high point of this rev range if not even furthur past this point, which is where the VCT switches off anyway. Therefore you can't add more boost. If i told you to make more power at 2500rpm on your car could you simply "add more boost and fuel" if your car isn't even on boost yet? No you couldn't.