Mating Rb26dett Throttle Plenum On Rb25det (neo) Head

[STATUS]

Sorry Guys but I fail to see the point of doing this modification. The factory rb25 intake manifold is good for at least 500rwhp worth of flow as I have seen. It will also give best cylinder distribution and will also create the highest port velocity due to the long runner length - which will result in a better midrange, earlier boost potential and not to mention better fuel economy.

I have dyno sheets of an aspirated XR6 with a TO4Z turbo conversion which I tuned a couple of months ago - as some of you are aware the aspirated XR6's have a dual length intake manifold to promote bottom end torque. The dyno sheet shows the difference between the long runner and short runner in a turbo situation and I can telll you the difference through the midrage is huge not to mention the rpm at which the desired boost level was acheived. If you interested I could find dig it up and post it.

I was lucky enough to be in japan at BLITZ when abe-san built the kits for nomuken's r34 gtt, i have the bosch dyno graph somewhere (this is the same graph used in the option magazine as they were also there to cover the kit) it lost no bottom end and gained 35 rwhp throughout the WHOLE mid to top end on a 400ps car.

i also bought a shload of these kits in 4 odd years back, few guys of here bought some like adzmax for "big red" and all have found killer results... pity they were dear and have since been discontinued.

[GTS4WD]

I was lucky enough to be in japan at BLITZ when abe-san built the kits for nomuken's r34 gtt, i have the bosch dyno graph somewhere (this is the same graph used in the option magazine as they were also there to cover the kit) it lost no bottom end and gained 35 rwhp throughout the WHOLE mid to top end on a 400ps car.

i also bought a shload of these kits in 4 odd years back, few guys of here bought some like adzmax for "big red" and all have found killer results... pity they were dear and have since been discontinued.

Strange how the Nomuken's American 34 still has the stocko manifold. I did notice that the other day.

Blitz's kit would of been a whole lot easier, but much more expensive. And not quite as unique and as technically advanced.

[STATUS]

Strange how the Nomuken's American 34 still has the stocko manifold. I did notice that the other day.

Blitz's kit would of been a whole lot easier, but much more expensive. And not quite as unique and as technically advanced.

the american car is one of the "old" spare cars.

[TriniGT]

I got the buckets out so now it's time remove the springs and whatnot, gonna leave the guides in for now and have everything done then have them replaced. Gonna have the head submerged in water and have the intake side be above water for welding to hopefully eliminate any heat problems. Any updates on your side, I am doing R32 Nismo twin turbos and 550 Nismo injectors on the RB26 fuel rail. I am also not filling the intake ports but reshaping the individual throttle adapter to match the bigger RB25 Neo intakes, there should be more than enough that I can machine off comfortably. Quick question for later on down the road, has anyone run a blow through setup on the RB25 as I am thinking of running this with twin setup using a Q45 MAF, your thoughts?

[1400r]

still got my blitz kit here

[TriniGT]

Why don't you make some copies? I can't see myself spitting out $2400 for it but it is a nice piece though. I am gonna try what I can on my spare head and see what can happen. Does anyone know how to go about removing two stuck valves, they are stuck shut, I am thinking maybe heating the head and removign the entire guide and vlave together, anyone has an idea what can be done, I don't want to be pounding on it hoping it pops free and damage something. All valves seals, springs, retainers, buckets etc have been removed along with valves except for these two valves, once removed I will get eerything welded and machined and tapped and then have the remaining guides removed and replaced and then have the entire head rebuilt. Also is it safe to drill and tap the exhaust side for the RB26 mani or should I just use the stock RB26 manis and have the appropriate flanges cut and flipped and rewelded, I have a good cast iron welder?

Edited January 7, 2009 by TriniGT

[T04GTR]

i knew that i should of orderd the $78 blitz gtr manifold adapter plate when i was at autobarn.. doh..

funny what you find in the system when your bored. i just typed in the search "rb26" and bang...

[T04GTR]

I got the buckets out so now it's time remove the springs and whatnot, gonna leave the guides in for now and have everything done then have them replaced. Gonna have the head submerged in water and have the intake side be above water for welding to hopefully eliminate any heat problems. Any updates on your side, I am doing R32 Nismo twin turbos and 550 Nismo injectors on the RB26 fuel rail. I am also not filling the intake ports but reshaping the individual throttle adapter to match the bigger RB25 Neo intakes, there should be more than enough that I can machine off comfortably. Quick question for later on down the road, has anyone run a blow through setup on the RB25 as I am thinking of running this with twin setup using a Q45 MAF, your thoughts?

you must have one big ass 300+ amp tig there!!!

[TriniGT]

Well I spoke to some people and got some more options but my friend that does the welding does a pretty decent job, this is the reason why I bought a scrapped head to do the job on in the even that it does fail then I still have my car running. Can anyone guide me as to how to remove the two stuck valves, should I just heat the area and tap the entire valve and guide out, I will need to replace all guides so I need some pointers on the difficulty of replacing the guides myself as finding good machinists locally is few and far between.

[GTS4WD]

i knew that i should of orderd the $78 blitz gtr manifold adapter plate when i was at autobarn.. doh..

Are you sure you arn't missing a zero at the end of that?

[TriniGT]

you must have one big ass 300+ amp tig there!!!

Oh just confirmed yeah 300+ amp tig FTW. I just spoke with him and he said he has done a number of heads and has some tricks up his sleeve, hopefully things go according to plan, he also has his machine shop that will be flattening the intake side and then tapping them as well. We'll see how it goes, this week I will be doing some valve guide work. GTS4WD thanks for the tips and I will keep in touch with my findings and results .

[GTS4WD]

Just keeping the thread alive.

Have run into a few problems;

Injectors - 25 are too small etc.

Problems with the coolent outlet fouling the clutch fan

But we are alsmost here with answers!

[dano4127]

Just keeping the thread alive.

Have run into a few problems;

Injectors - 25 are too small etc.

Problems with the coolent outlet fouling the clutch fan

But we are alsmost here with answers!

yeah i was thinking that when i saw the photo!!

[GTS4WD]

yeah i was thinking that when i saw the photo!!

It wasn't a major set back, but it was just another thing we had to deal with.

[TriniGT]

I don't see both problems being a big thing and can be easily solved. The coolant outlet is a quick fix and also I was thinking you should have gone with RB26 injectors and the resistor pack. That is what my plan is, should be getting back my head soon from the shop, as soon as weekend hopefully.

[MBS206]

Top feed injectors, so much easier to change! Go with GTR rail!

As to the coolant issue, just throw a thermo fan on instead!

[GTS4WD]

Hoookay.. so.. update!

Photos of the finished head, all filing, grinding etc completed. Did also some minor porting & polishing, mainly removing casting imperfections.

The face was also machined.

Please note that the "kink" at the top of the RB25DET head port needed to be enlaged too.

Note the stud which replaces the original bolt on LHS of the water port hole.

The coolant outlet was chopped and re-welded, having now the correct position and clearance against timing belt cover, plenum, VCT solenoid and fuel rail and clutch fan clearance issues.

Note the outlet is at a greater angle than before

The 'air balancer' above the manifold had interference as shown. Same for the bottom of the water gallery under the manifold, which required bit of filing as well as grinding the head of the LHS bolt.

More grinding on the block, the thermostat housing and the top bolt to ensure clearance with the water gallery below the manifold. The yellow water tube on LHS was also rotated few degrees down due to interference.

As you Can see there is very little grinding required.

Decided to use at this stage the NEO injectors and rail, to be able to start and run the engine on the stock ECU and iron out any other 'bugs'. The injectors have been modded as shown, with nozzle sitting now in same position as the GTR injectors. The rail brackets are also being modded with more photos to come shortly.

Long term will push for more kW with GTR rail, adjustable fuel regulator and aftermarket ECU (ye ol' faithful PFC sitting at home)

The NEO oil cooler interferes with the air box below the plenum. Most likely we'll replace this with a GTR oil cooler, although down the track an external oil cooler will be fitted.

Will most likely have to go with the GTR AAC valve, as the NEO one is very different.

Yes it was possible to thermo fans, GTR rail, injectors and play around with the ijector impendance but that would be adding a considerable amount of cash the project as well as adding extra injector problems.

[Kaido_RR]

you will have to use the gt-t AAC valve, as the gt-t uses 2 plugs on it but the gtr only uses one.

GTR injectors and rail is easy, you just wire in the std gtr resister pack, and gtr injectors are cheaper than gt-t injectors.

i am running a hks oil cooler but i still found that the vacuum box that is bolted onto the under side of the gtr plenum would not fit, so i fab up my own mine and hook up all the vacuum hoses that were needed into it

Also looks like you use the GTR water outlet on the plenum the other option you could have gone was to cut off the gt-t water outlet and weld that onto the gtr plenum. then the angle would not have been so bad but looks like it will still work.

Edited February 17, 2009 by [Michael]

[rsmagnum]

Interesting thing to do.

Have you dynos before/after later when your done?

[Kaido_RR]

my before and after results were

Before:

Full boost @ 16psi 3300rpm

After:

More power

More torque

More responds

Full Boost @ 18psi 3200rpm

different dynos where used; second dyno reads lower than the 1st dyno but still made more power.

The car changed characteristics greatly; the car gain alot of responds; no matter what gear or were you were i the rev range. The car was tune very soft, still has alot more in it but i choice not to push it; plus @ the time of the tune still had an exhaust leak

Edited February 17, 2009 by [Michael]