Neo Head On Sii Block Questions & Concerns ! (rb25det)

[stricnynel0s]

OK, for my insane build i am gunna be getting another Head, basically a NEO head for a couple reason

1) Solid Lifters

2) Can get it machined with less downtime

3) VVT

Ok, my questions are will there be any issues with head stud location using this new head ? or oil and water lines ? also wut about the wiring for the vvt, i know the sii has NVCS which is only on inlet cam and the neo has it both, also i am not using a stock ecu i am using a haltch e6k, my plan is to get the head, take to machine shop get it polished, ported, remove squish area (per JUN) ...actually gunna do EXACTLY wut they did as listed here http://www.junauto.co.jp/processing/rb26/index.html html, but withouy all the fancy jazz will the head bolt on and will the vvt be working with minor wiring or any at all

[stricnynel0s]

bumpity bump

[Bass Junky]

The Neo only has VVT on the inlet, just like the R33.

You will have to be careful, as the Neo head is considerably different to the R33 head.

I think almost to the point of not being compatible with the R33 block.

cheers

Pete

[stricnynel0s]

The Neo only has VVT on the inlet, just like the R33.

You will have to be careful, as the Neo head is considerably different to the R33 head.

I think almost to the point of not being compatible with the R33 block.

cheers

Pete

hmm i was told it has it on exh as well as the intake hmmmm here aresome pics of the head

[Bass Junky]

I'm here to tell you that you have been mistaken.

Inlet only. But apparently its not just on and off like the R33. It's variable.

[Bass Junky]

PS. Only one pic working

[stricnynel0s]

PS. Only one pic working

ahh yeah the other pics u gotta copy and paste hehe... hmm this sux for me now hehe, at least i get solid lifters out of the deal

[Bass Junky]

I think that the best thing to do would be to sell the head and buy an R33 head.

to many HEADaches otherwise

[Adriano]

Head and manifolds will bolt on as they are they same bolt pattern as r33, everything else lines up to r33 block, dont forget to use oil restrictors. VVT is on the inlet cam only, but it is variable, so to control it properly, you need to use a 3d map with a PWModulated output, which your computer doesn't have. Also your CAS will not bolt to the exhaust cam. If your going for something extreme, im assuming you would put cams in. R32 gtr cams fir and allowyour cas to bolt in, but you will lose the vct, just fit some camwheels, as it will be heaps cheaper then trying to setup the vct on the dyno with a shipload of load pionts that need to be setup. Also dont forget you will need completely different pistons as the neo has much smaller combustion chambers which will increse to compresion rtio by approx 1

[Bass Junky]

Adriano.

I thought the Neo head wouldn't fit for some reason. Have you fitted one before?

The Neo also has the same compression as R33...... How could it change compression?

[Adriano]

Yes ive fitted one to an rb30. Neo's have flat top pistons and a small cc in the head, wheras r33's have dome pistons and a larger cc in the head. It is about 11cc difference, so if you ran a neo head with r33 pistons the c:r will end up at 10:1. Also the nea has bigger inlet valves.

[Bass Junky]

Adriano.

Cool, thanks. That's very informative.

Any other info?

What's the casting like? gains to be made from a tidy up?

[Adriano]

The casting is pretty good, i wouldn't bother porting it unless you are after 700hp or more. A set of 2nd hand gtr cams with the aerospeed camgears will be a pretty good setup athough you wil lose a small amount of lowdown torque due to the bigger cams and no vct, but you really end up with a gtr head without the hassles of manifolds.

[Bass Junky]

What's the duration etc of the GTR cams?

I have the Tomie 260 x 9.15mm....

[stricnynel0s]

now that i didnt know, refering to the combustion chambers, i am running a rb26 crank, with machined rods from thagards speed shop, and wiseco 87mm rb26 pistons so i am at 8.0ish, i would love to be 9.0 but the vvt issue really converns me, do u think it would be wiser to just keep the nvcs that is on the rb25, and use the neos solid lifters, and buy the tomei procams which require solid lifters

[Bass Junky]

Yeah I reckon put the poncams in, or Neo specific cams.

That way you keep the NVCS and all that.

[Adriano]

Obviously neo specific cams would be preferred, especially if you get poncams or such, however if you dont have a computer that can control it then the variable vct is wasted, especially if the cams are ground to siut the vct. Also a r32 and early r33's have a different drive to the cas on the front of the exhaust cam, so you need to see which drive you need for your cas. If you need to get rid of the vct, i would get an r32 gtr inlet cam, with a camwheel, as it is cheap, adjustable, and has fairly good lift and duration. On the exhaust i would run whichever cam you need to run your cas

[discopotato03]

Does anyone have pics of the Neo RB25DET chambers and piston crowns just so we can compare .

Thanks A .

[Spoolup]

I have a NEO head on RB30 bottom end, running HKS 272 / 9.35 cams.

Im using the the R33 CAS with the cams, as its in a R33 4 door with power fc. Like Adriano said, they are a smaller combustion chamber with VCT on the inlet only, not that Im using it. As for stricnynel0s, dont stress too much about the VCT as RB26's dont use it and they make enough power with out it :-)

[Stronzo]

i have NEO 25det controlled by ECR33 ecu. NVCS is wired correctly and working in some way -- i`ll try to disconnect it and try to see the difference .