Rb30/25 Conversion Questions!

[N0Vus]

Hey all im getting into my rb30 build, and have some questions I havent been able to find answers for.

Firstly, any difference between the R34 RB25DE head and the R34 RB25DET Head?

From what I have read neo heads are the way togo but, there has been some question about port sizes between the 25det and 25de neo heads?

Will running a Neo head require different pistons? Compared to if I ran a R33 RB25DE VCT head? As im about to order some CP Forged pistons and dont want to run into the problem where I pick up a Neo donor motor and sell my r33 rb25.

Anything else I need to know? Running the R33 head I know I have to run a external vct oil feed etc, is this all the same with the neo head? or do I need to further modify the head?

Cheers, Liam

[Ben C34]

Alllllll of this is info you can search and find.

Combustion chamber volumes,

Camshafts

Port sizes

Modifying neo head for external vct.

Differences with wiring and cas between neo and non neo

Etc

Have you even tried?

Don't get me wrong, I am happy to help but you need to show you tried!

There are recent threads with photos of neo head vct mods.

[N0Vus]

Yeah I used the search feature of the forum, and came across threads that went the wrong direction and talked about other things.

Either im using the wrong keywords to find posts but I haven't found much, may possibly be using the search feature incorrect.

***EDIT: Ive also been sifting through google for the last 2 hours.

Came out with more questions then answers, there is alot of incomplete information regarding use of the neo head.

Edited June 26, 2014 by N0Vus

[Blackkers]

pistons shouldn't matter unless you're running stupid amounts of lift. 25det neo cams have higher lift than the r33 25 stockers.

VCT shouldn't change although for the R34 head you don't need an oil restrictor in the feed. I'm not sure if it really matters on the R33 heads anyway, someone else probably could answer this.

The DET heads are much more suited to boost in their factory form as I'm sure you know.

[N0Vus]

I havent found much about the R34 heads. Like I know the r33 de/det are the same, so I originally opted for that, but now my quick 30det build has become a forged build, so im looking into the NEO head for the better flow. The main question I really need answering is, are the de/det neo heads the same? as i said before theres been mention that intake ports are alot smaller? but then other pepole have questioned this saying that the comparision i was viewing was 25 vs a 20neo

[Ben C34]

Ok.

I will help.

The De and det neo heads are heaps different.

Port size and cams.

I wouldn't use the De head.

[Ben C34]

And on the first page of of this section there's a thread called vct external feed . 2nd last page pics of neo head modded. Found them by just looking x)

And threads on neo 2530 builds.

Use Google to search.

Add Site:/skylinesAustralia.com

To find results from this forum, as the forum search engine sucks.

[N0Vus]

Thanks heaps! Ok looks like Ill be using my r33 25de head. The only way id get a neo head is to actually buy a whole 25det motor

Can the neo de ports be ported out to turbo spec? and cams arent a big deal as they would most likely be swapped out


Yeah the vct oil feed stuff I already knew, but was double checking it wasnt different with a NEO head.

Thank you for helping Ben!

[Jiimmii]

Where you you from? Have you looked on gumtree? There's a whole 2530 conversion on gumtree, comes with vls2 engine, rb25det neo head, few other bits and pieces, there's even a 25det motor on ebay for like 500 bucks has low comp but only need the head,

[Jiimmii]

I might sell ya my 25det head, has a bit of det but can be fixed, has adjustable cam gear, the rest is all stock, 163713k's, was going to use it for my 2530 build, but wouldn't mind just getting back on the road

[N0Vus]

Im in New Zealand

[KiwiRS4T]

Have you read the RB conversion guide in the first thread in the RB30 section?:

http://stevenwelsh.site.net.au/RB30_DOHC.pdf

That has almost everything you need to know.

Where abouts are you?

Make sure you order the H/c pistons (9:1 not 8.2:1)

[Ben C34]

You need to know what head you are using before ordering pistons.

[N0Vus]

Ok im sticking to the R33 Head, To much hassle and extra costs related to get the R34 25DET head which I guess leaves some extra money towards cams.

These are the same as what Im looking at LINK.

Should I be getting 9:1 over 8.2:1?

This is my first build, and I was told slightly lower wont do any harm?

But I guess if someone with experience with the same build can tell me other wise Ill take that knowledge!

[KiwiRS4T]

NZ Performance can also get you the 9:1

Your choice - you'll get more power with the higher comp.

[R32Abuser]

IMO you need to decide on a few things first:

Power target?

Street/Track (spilt 90:10, 50:50)?

Stealth or Show?

For example, there is no huge benefit going a forged bottom end if you are shooting for upto 300 RWKW. Sure, its a nice to have and it gives you a bit of insurance, but its not necessary IMO.

If you're shooting for more power, then sure...But even then, look at SimonS14's drifter - was/is running 350-400RWKW with a std RB30 bottom end. If he blows it, just change out for the grand total of <$150 in parts.

All of it is in the tune - run it on the edge, and you will get stung. This will happen with a std bottom end or forged.

As stated above, building forged just gives you a bit of tolerance for a less than OK tune.

Take it from someone who has built a RB30DET (forged), if I had my time again, I would have using a GTT Neo head. Its pretty much better in every way than previous RB25's. Also, if memory serves, using a Neo head with a std RB30 bottom end gives you a static CR of about 9:1 (maybe a touch more). This is fantastic for off boost response, something which is important on the street. You won't get a 9:1 static CR with a R32/33 RB25 (due to the combustion chamber size) unless you change your pistons. Skimming the head might bump your CR up, but I don't believe you would get 9:1 using a std RB30 bottom end.

The above is my 0.02c, but just trying to offer hindsight to someone who hasn't gone down the path!

[Ben C34]

What he said!

[N0Vus]

Here in NZ, Rb30's are very hard to come by so its not as easy as $150 worth of parts, when you'd be lucky to pay less then $300 for a bare block

I was planning on building it to around 350-400kw, for use on the road and to try get on the track as much as I can. Hoping it will be something I don't have to worry about to much in the longer(ish) run.

And I dont have the standard pistons, only the rods.

So you are pretty much saying if im only after 350kw, stick with std bottom end and put my money into the Neo head?

On the other side of things, by the looks of things the only way im getting a RB25DET Neo head is by buying a complete motor.

Thanks for all the feed back everyone, helps alot.


***EDIT

Ok, so Im thinking I will leave the pistons for now and see if I can get a hold of a 25DET Neo head. As R32Abuser said, the higher compression is better for off boost, which I understand. So my next step is, since I dont have stock pistons I will probably get some forged ones to achieve static 9:1CR and I suppose a bit of piece of mind to know I have a good set.

So should I run with stock rods or get forged rods? As I said im after 350-400kw, but will be good to have something capable of handling more as I dont see my self getting rid of this motor once built and would like the option of going further as years come by.

Edited June 28, 2014 by N0Vus

[KiwiRS4T]

If you read the RB30 thread you will know that stock rods are very substantial. You should get new bolts for them though.

[R32Abuser]

If you read the RB30 thread you will know that stock rods are very substantial. You should get new bolts for them though.

Stock rods are fine for his target.

However, by the time you price them up to go with aftermarket pistons they end up costing almost as much as a forged 4340 set from SPOOL or similar...Or at least they did when I went down this path!

http://www.spoolimports.com/spool-conrods/nissan/rb30-conrods/nissan-rb30-conrods