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Rb25/34

Morgz32

By Morgz32,
in Engines & Forced Induction

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Morgz32 Collaborator

Morgz32

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hey guys

im in the works of planning a 25/34 build to go into my 34 GTT, im sourcing parts prices etc but one thing that im questioning is the neo head. Ive built a 25/30 for my 32 using a 33 series 2 head which i got the water gallery welded, and a external oil feed for the lifters is the neo head requiring the same work? im sure the water gallery has to be welded but is there anything different between a neo head opposed to the 33 head that needs to be addressed for this conversion??

thanks

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Morgz32 Collaborator

Morgz32

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would it be worth using a 33 series 2 head? i assume the majority of the 34 wiring harness is the same as the 33?

i had a 25/30 in my 32 originally had a 25 in it, and when i got it tuned the tuners said it had a 34 wiring harness

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jangles Veteran

jangles

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would it be worth using a 33 series 2 head? i assume the majority of the 34 wiring harness is the same as the 33?

i had a 25/30 in my 32 originally had a 25 in it, and when i got it tuned the tuners said it had a 34 wiring harness

34 head is far better, just allow for the 34 when choosing pistons etc.

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KiwiRS4T Grand Master

KiwiRS4T

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what do you mean by allow for the 34?

What Jonathon said - the Neo head has a smaller combustion chamber than the R33 so you need to take that into account when calculating your compression ratio. Should be fine with the extra capacity of the 3.4 block - Neo is the superior head. Look forward to seeing the result!
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r33_racer Grand Master

r33_racer

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The lifters will be fine. Just use the correct oil restrictors. We converted our r33 s2 head to solids and I made two 1.1mm restrictors using m8 grub screws. Has worked fine so far. This is on a spool rb34 stroker also.

As they said already you just need to cc your chambers and get the pistons to suit so your compression doesnt go sky high. Otherwise no worries!

Be prepared for a nice fat torque and power curve. From our old rb30 our whole power curve moved to the left by a good 1000rpm and we picked up something like 160hp more through the midrange. Makes the car so much nicer to drive.

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harks Collaborator

harks

Posted
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what is the approximate additional cost in block prep to fit the 34 crank in? the spool site mentions there is some minor modifications required to make it fit.

i'm looking at a 26/34 conversion into my 32 GTR down the track (when i get the $$ for it) was weighing up a 2.8 stroker but leaning towards going all out with the 34 since im more looking at low end torque and dont want to wait till 4.5k rpm for boost.

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KiwiRS4T Grand Master

KiwiRS4T

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ahhh ok that makes sense im getting a spool kit for my build, out of curiosity what did you set your compression ratio at?

thinking of using a JUN pump

Mine is a bargain basement build with stock pistons resulting in about 8.2:1 CR :/

As yours will be fully forged etc something well north of 9:1 or even more if you are going to run E85 would be good!

I have an N1 pump but don't limiter bash and have 7000 max rpm.

Jun sounds good - Tomei may be better but people swear by Nitto pumps - no experience of them myself!!

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KiwiRS4T Grand Master

KiwiRS4T

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what is the approximate additional cost in block prep to fit the 34 crank in? the spool site mentions there is some minor modifications required to make it fit.

i'm looking at a 26/34 conversion into my 32 GTR down the track (when i get the $$ for it) was weighing up a 2.8 stroker but leaning towards going all out with the 34 since im more looking at low end torque and dont want to wait till 4.5k rpm for boost.

The pictures on their site show a small amount ground away for the extra clearance needed for the 3.4 - looks like a very small job - less than 15min labour.

Go the 34 - I want to see more results!!

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MRHD66 Rising Star

MRHD66

Posted
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The pictures on their site show a small amount ground away for the extra clearance needed for the 3.4 - looks like a very small job - less than 15min labour.

Go the 34 - I want to see more results!!

spool RB32 don't need any clearance and unlike the nitto RB32 stroker the spool on is a 3.2l
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JonnoHR31 Grand Master

JonnoHR31

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spool RB32 don't need any clearance

So? The extra capacity of the 3.4 comes from a longer stroke. Longer stroke means a larger diameter crank, which naturally needs more room to spin around.... What's your point?

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MRHD66 Rising Star

MRHD66

Posted
Posted (edited)

So? The extra capacity of the 3.4 comes from a longer stroke. Longer stroke means a larger diameter crank, which naturally needs more room to spin around.... What's your point?

was just saying some people don't like machining the block for Clearance as it weakness the block a bit Edited by MRHD66
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blue_vl_t Rising Star

blue_vl_t

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It will be interesting to see more results, I've only ever come across the spool s15 dyno graph. It's a good thing. Is there any other 3.4L results you guy know of?

I like the idea of the 3.4, considering its really the same cost as going 2.8 from a rb26, obviously exept the mods to fit an rb 30 in your car.

What rpm are you looking to turn this to?

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