Jump to content
SAU Community

Recommended Posts

I am pretty sure nothing needs to be changed, you may need lower mounts as the rb30 bottom i think is 38mm bigger. I am also sure rb25 pistons will fit but may not be the best option you should go with, forged pistons will definently be the best option.

Aftermarket ECU is a must have and with a dyno tune you should be set mate.

this is exactly what im going to be doing, but i will be smacking GT35R on the side of mine :(

The neo head has slightly smaller combustion chambers than the normal rb25/26 head, its somewhere around the 60cc per pot compared to 64ish cc in the normal head. This makes quite a bit of difference to the CR.

With the na rb30 pistons, a deck block, thin hg and the neo head, that would have to net around the 10:1 if not higher. I think the na rb25 pistons might be a tad too much but just grab one of the online CR calculators and start plugging in numbers and you'll see what you'll need. I havent really looked that much into the na side of things since will be going the turbo route, but with mine acl rb30et pistons, neo head, decked block and a 1mm hg will get around the 8.5-9.0 CR mark. Obviously with the na route you would want much more than that

if you are using the neo head and want a high compression turbo motor (RB30DET), grab the flat top CP pistons that spool sell in his kit for the normal rb25/30. Depending how you set up the motor, you'll get anywhere from 9.0 to 10:1 CR, i doubt you'll want more than that

I want mine around the 8.8 mark, still responsive but will still like some boost :)

Im aiming to run everything as standard just with the 30 bottom end and 25 pistons switched. Then a safc will prob do for the extra fuel. Wat machining is required? and do i need a better oil pump than the vL one?

You will need water pump collar and to relocate a pulley.

Google "RB30DET" and .pdf. there is an awsome file out there.

i'm going to take a stab in the dark and assume you meant oil pump collar instead, but thats only if he uses a widenose gtr pump :D

Edited by R34GTFOUR

if its going to be a daily the rb25 pump will do the trick, you wont need the crank collar sine the rb25 runs a narrow nose crank like the rb30

If you are going to spend abit of $$ on the conversion and track it abit, an upgraded oil pump is good insurance

  • 3 years later...

before this goes any further, and before a motor blows up

a neo head has a smaller chamber, ive measured them between 52 & 55ccs

in the tech section there is a simple maths formular i wrote up to work out your actual compression ratio, guessing = problem waiting to happen

flat tops with neo head estimated around 9:1 static

  • 2 weeks later...
  • 1 month later...

before this goes any further, and before a motor blows up

a neo head has a smaller chamber, ive measured them between 52 & 55ccs

in the tech section there is a simple maths formular i wrote up to work out your actual compression ratio, guessing = problem waiting to happen

flat tops with neo head estimated around 9:1 static

So as OP posted what kind of compression it will reach Neo head and 30 block, couldn't find the answer and really bad in calculating compression I am looking around 11 for my NA setup

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Hang on. Let me get this straight. The desire is to have coilovers, BC in particular, to be MORE comfortable on Sydney roads than stock suspension? Well, that's obviously not right. BCs have crude damping design at the very best, and typically hard spring rates. BC stands for Billy Cart. And then, the desire is to put in some shitty old worn out stockers, to get it blue slipped and then put the BCs back in? And then.....what? Not worry about getting pulled up by the Plod? Because you seem to have raised a worry about paying for engineering (which actually does solve all your legality problems) and still getting pulled up.... but the only problem there is that if/when that happens you have to show your paperwork at the inspection station. Whereas, if you just swap in borrowed shitty old stockers to get it slipped now, and then you get defected in the future, you have to go find more shitty old stockers then too. You course of action looks like this set of options: Buy brand new stock type dampers, and springs. probably cost a bit more than $1k all up, but will last for the remaining life of the car. Put them in, pass inspection, drive on them forever more. Hell, they could even be really nice Bilsteins and Kings or other lower&stiffer springs if you wanted. Get the car engineered as is. ~$1k. Buy new Shockworks coilvers (or MCA) and also pay for engineering. You're spending a lot more here. But these will be the best things that you could drive around on.
    • Might be worthwhile hitting up Facebook's groups, I know most of them contain terrible people and scammers - however you might be able to find someone that's in Sydney with factory suspension you could purchase and/or hire. Just do not send any form of money anywhere, in person cash only.
    • Thanks @Duncan Ride height is fine. I think it's almost stock tbh. Happy to share a pic. I don't actually have a regular mechanic as haven't lived in Sydney too long. Could you or anyone recommend any shops in Sydney?
    • You just need a different blue slip shop (preferably one you regularly use as a mechanic), and make sure the coil overs are as close as possible to standard height
    • yeah the sugar refining companies were pushing for the same in Oz originally, all fuels were going to have 10% ethanol to make them "cheaper" (noting, that the loss in l/100 might be greater than the decrease in price). I guess they won that fight in Canadia
×
×
  • Create New...