Rb26 Neo

[sneakey pete]

The engine in my '32 GTR is in need of a rebuild and i've decided to go all out on it (all the goodies, stroker and the like), one of the thing's i've been considering is VCT.

Option 1 for installing VCT would be to grab the kit from Otomoto, which is 3K, plus the required NEO bits, which is around another 650 by all accounts, give or take. Given this is a rebuild most of the other work required would have been done anyway so not really an extra cost there.

However, i've had some suggestions from around the place that perhaps I should buy a Rb25 NEO and swap the heads over. I've not heard of anyone do this, and there would be a number of things to sort out but it may work out significantly cheaper in the end, however there are some things that i'm struggling to get my head around.

From what I understand, the main things that would need to be sorted.

• Exhaust: i'd be keeping my twin turbo setup, so cylinder 2 and 5 need to be changed, this would best be done by drill+tapping new holes in the head, correct?
• Cam covers: swap over all my 26 stuff, does it all bolt on? Obviously the timing belt cover would need some adjustments, have some ideas with that.
• VCT oil feed. As i understand this, the 26 block would have the same issues as doing a VCT on a 30 block so i could use the solutions used there, which is an external feed as i understand it, however i've also seen some info on people drilling oil feeds into their 30 blocks to avoid needing an external oil feed for the VCT. Am I barking up a good tree here?
• Headstuds: I understand RB26 ones are larger, so this would just require re-drilling the holes on the NEO head?
• Intake: this is the big one. I would want to keep the ITB's, so this would require welding a new inner runner section using the existing runner to NEO flange and with the runner to TB flange from the 26 on the other end, keeping a similar length and all the water lines etc. I've talked to a fabricator who believes he can do it but any advice/experience here would be helpful. Obviously the main issue would be to keep the length in check as i can't afford to have the plenum space out any further.

Is there anything else am I missing here?

I understand that the NEO head has some design revisions, eg larger exhaust valves from factory, hopefully these would be a net positive to the engine also, is there anything else there which may come into play, eg changes with oil return? Obviously the head will be refreshed and cleaned up with new valve springs etc, and possibly some cams, but this is something that would happen with either head.

Why am I trying to do this? Well, the net cost to me from getting the neo, offloading the bottom end and other ancillaries and the 26 head would probably be 1000 bucks, so even if the extra fabrication and machining work to set it all up is 1-2000 i'm coming out ahead compared to the Ottomoto kit, which is nice.

[XKLABA]

Get someone to post a graph of VCT on v VCT off overlaid

You may just find the gains if any over properly dialed in cams are not worth the cost

[sneakey pete]

Hnm, a lot of people rave about vct. I'll try and drive a mates car with vct on then off soon.

obviously that's a bit different to a car with properly dialed in cam gears but i'd be getting adjustable gears for the vct head anyway so that may be a moot point, its more about the difference the vct would make, particularly to transient response.

[Dose Pipe Sutututu]

probably not a like for like comparison, but drive a R34 or R33 GTS-t with moderate mods/power, then unplug the VCT solenoid plug and then drive it

[GTSBoy]

It's not fair to do the comparison with it enabled and disabled. An engine that is intended to not have VCT will more than likely have fixed valve timing part way between the advanced and retarded positions that the VCT will give. Having VCT enabled means that the engine will feel better at both the top end and bottom end than the engine that doesn't have VCT. Having VCT disabled will make that engine feel better than the non VCT engine at one end of the rev range, and much worse at the other.

[KiwiRS4T]

You can usually only put an adjustable cam gear on the exhaust of a VCT head. It is possible to adjust the inlet side but a lot of stuffing around and generally not worth it on an RB25 - no idea what it would be like on a 26.

[sneakey pete]

I've seen an adjustable gear that has been made up that is pretty easy to adjust, only in the last few months, would more than likely be grabbing one of those.

  On 18/11/2015 at 6:46 AM, GTSBoy said:

It's not fair to do the comparison with it enabled and disabled. An engine that is intended to not have VCT will more than likely have fixed valve timing part way between the advanced and retarded positions that the VCT will give. Having VCT enabled means that the engine will feel better at both the top end and bottom end than the engine that doesn't have VCT. Having VCT disabled will make that engine feel better than the non VCT engine at one end of the rev range, and much worse at the other.

Yes you're right, at least it might get me an idea of the difference it would make

[XKLABA]

I believe Ben with a Stagea on here makes adjustable gears for the VCT

My idea of doing it on a dyno is it should/will clearly show any gains top or bottom end

The reason I am not convinced of just VCT especially only on intake is to the best of my knowledge the adjustment goes from one end of the adjuster to the other end which could very well go past the optimal cam angles for top or bottom end power when a fixed set cam in between the different optimal angles may just give a good as or even better result then VCT

Or even good enough to justify not spending $3500-$4500 to fit VCT to one cam

Getting a VE setup on the other hand would be tits

[WMDC35]

GReddy does an adjustable gear for VCT

[iruvyouskyrine]

BenC34 makes an item that makes your inlet cam gear adjustable from the front. Only $40 or something from memory and it works a treat on my car.

[stealthfoz]

what sort of HP are you planning on running? a set of aftermarket cams with adjustable gears "properly" dialed in will probably give you what your after without spending so much$$$$ for very little, if any, gains.

you cant compare a car tuned with vct by just disconnecting it and seeing the difference as you will definitely feel the difference as its set up to run vct!

very hard to compare as every car will "feel" different and react different on the road

[sneakey pete]

Power should be around the 550 mark, Turbos are going to be gtx2860s. Aim is for getting them on song as quickly as possible.

[sneakey pete]

Ignoring the discussion on the merit of vct, does anyone have any comments or insight about the actual process of mating the NEO head to the 26 block?

  On 17/11/2015 at 6:34 AM, sneakey pete said:

From what I understand, the main things that would need to be sorted.

• Exhaust: i'd be keeping my twin turbo setup, so cylinder 2 and 5 need to be changed, this would best be done by drill+tapping new holes in the head, correct?
• Cam covers: swap over all my 26 stuff, does it all bolt on? Obviously the timing belt cover would need some adjustments, have some ideas with that.
• VCT oil feed. As i understand this, the 26 block would have the same issues as doing a VCT on a 30 block so i could use the solutions used there, which is an external feed as i understand it, however i've also seen some info on people drilling oil feeds into their 30 blocks to avoid needing an external oil feed for the VCT. Am I barking up a good tree here?
• Headstuds: I understand RB26 ones are larger, so this would just require re-drilling the holes on the NEO head?
• Intake: this is the big one. I would want to keep the ITB's, so this would require welding a new inner runner section using the existing runner to NEO flange and with the runner to TB flange from the 26 on the other end, keeping a similar length and all the water lines etc. I've talked to a fabricator who believes he can do it but any advice/experience here would be helpful. Obviously the main issue would be to keep the length in check as i can't afford to have the plenum space out any further.

Is there anything else am I missing here?

I understand that the NEO head has some design revisions, eg larger exhaust valves from factory, hopefully these would be a net positive to the engine also, is there anything else there which may come into play, eg changes with oil return? Obviously the head will be refreshed and cleaned up with new valve springs etc, and possibly some cams, but this is something that would happen with either head.

[chiksluvit]

Isn't the neo internal almost the same as 26 anyway?

[Stixbnr32]

Just go HKS V-Cam....screw the cost.

[GH05T]

http://www.hks-power.co.jp/en/product/engine/rb26_vcam/index.html

a few graphs albeit marketing stuff.

[Pr0x1mity]

Why not a 30 bottom end too then?

[sneakey pete]

Won't fit in a 32 r without modification of the bonnet

[Dobz]

I'm looking at doing the same thing when I get off my arse. I'm looking at putting the vct straight onto the rb26 head. Using rb25 neo IN cam and vct. I've drawn up a little external solenoid housing that would eliminate the need for it to mount in the head as rb25 neo does.

The oil to the vct will replicate the rb25 neo. I've already moved the cam journal lube hole to the side just like the 25 neo, all that's left is to mount a compression fitting atop #1 IN cam cap to feed the vct cam gallery. 3/16 copper pipe can snake to the back of the head using mounting tabs on the cap bolts and it could exit via a hole through the rubber half moon.

With how much difference there is with the rb25 neo vct on and off surely there are similar gains to be had with the 26.

If you can afford it go V-cam.

[R31Nismoid]

NEO head, do it. More and more are doing it - for good reason. Or go V-CAM... There is someone making a V-CAM without the HKS price, for the life of me I cannot remember who it is though.

Pete - I can't confirm most of your points except intake. Just get a NEO / ITB throttle plate adapter. There are people that make them, I think like $800 - job done and it's bolt on.

Just shave some material off the plenum you're installing and you're off and running. Even the plate itself - depending on how many mm you need.