Rb25/30 Na High Comp Build Up

[unarmed_skyline]

Sweet keep us posted

[GTS4WD]

Head pics will be up HOPEFULLY this weekend..

Linda been screwed around by the buyer for a while..

But its still alive and well..

[GTS4WD]

Well..

Picked up the head..

Dont be turned off it.. It needs a good clean but internally its in very good condition.

Now.. I have a question.. Is this a VVL head? Because I noticed that it has the enlarged ends at the cam shaft covers. I noticed that my dads RB25DET VVL has these too. Below is my RB25DE head out of a Staggy or 33. Note that its Does not have the same bulges comming out of the the camshaft covers.

Ideas?

Thanks guys!

Project is still alive.. just a slow build

[inthisglass]

i like the cat

[ignuz]

Nice work mate, I'm gunning for you..

There's a guy on ns.com with semi worked N/A pulsar and he ran 14.3 at WSID.

Let's see you hit 13's!

[Eug]

i might be joining you very very soon... blew a gasket on the weekend and i'm trying to justify as using this as an excuse to build one.

i've got a RB30 block sitting at home now and someone who is able to fabricate RB26 throttle bodies onto the RB25 head.

taking donations!!!

Cris, we will need to have a good chat about this sometime after May.

[Eug]

i'm looking to something like what don has done but with a few more good bits. the more i price up a proper rb30de the gains are simply not worth it, i will most likely do a rough build for a side project and will hopefully be making 200rwkw on an na motor by late next year

[GTS4WD]

i'm looking to something like what don has done but with a few more good bits. the more i price up a proper rb30de the gains are simply not worth it, i will most likely do a rough build for a side project and will hopefully be making 200rwkw on an na motor by late next year

I know what you mean..

I called around for few places on quotes on balancing the bottom end etc.. and there is a lot of money spent of parts and work that dont necessarily yeld many gains. And, as with all builds/ mods.. I know for a fact im going to hit a problem.. its impossible to do anything without hitting a problem.. Then there are all the random bits and peices.. hose, clamps, re-wiring, brackets etc. that can't really factor in because you dont know that what you need.

On top of that.. there are all the driveline/brakes thats need attention too.

What kind of parts are you looking into? Because im budgeting alot of second hand/Nissan items.. DET/GTR parts

Rb26 TB's? As in the intake manifold? or Individual Throttle bodies? I had a look at ITB's (i think if im going to do an NA build i should do it right with ITB's) but off the shelf items are very expensive..

How hard would it be to make your own indivitual throttle bodies?.. I have a metal work ladth at home.. Or is a CNC/CAD job?

Edited April 28, 2008 by GTS4WD

[Eug]

I know what you mean..

I called around for few places on quotes on balancing the bottom end etc.. and there is a lot of money spent of parts and work that dont necessarily yeld many gains. And, as with all builds/ mods.. I know for a fact im going to hit a problem.. its impossible to do anything without hitting a problem.. Then there are all the random bits and peices.. hose, clamps, re-wiring, brackets etc. that can't really factor in because you dont know that what you need.

On top of that.. there are all the driveline/brakes thats need attention too.

What kind of parts are you looking into? Because im budgeting alot of second hand/Nissan items.. DET/GTR parts

Rb26 TB's? As in the intake manifold? or Individual Throttle bodies? I had a look at ITB's (i think if im going to do an NA build i should do it right with ITB's) but off the shelf items are very expensive..

How hard would it be to make your own indivitual throttle bodies?.. I have a metal work ladth at home.. Or is a CNC/CAD job?

it seriously is one of those motors where the maths doesn't add up. unless you have a heap of spare parts lying around the shed it's simply not feasible.

balancing is such a crucial thing and you are right it doesnt net you any direct gains, however it gives you more reliability and the ability to rev it harder which ultimately gives more power.

i currently have another NA motor in mind, one that will make 200rwkw all day everyday without even maxing out its potential and would be perfect for racing. hence why i'll probably opt for a cheapo RB30 build, would still be looking around 130-150rwkw i would imagine.

driveline and brakes shouldn't be an issue with me, they've all been upgraded.

at this stage i'm still tentative, there's alot of stuff i've yet to consider. where can i skimp on things? which is important and most importantly the fact that i'm working with a budget. i would be in the same boat as you, i'm looking into using the head off my current motor due to the fact that i already have extractors and dont/wont need to buy an RB26 head.

the adapter will allow RB25 users to bolt on the RB26 intake manifold (throttle bodies inclusive) onto the RB25 head. it's significantly cheaper than buying an RB26 head. this will give the option to take off the intake manifold and bolt trumpets on if i want to. although at this stage i dont think i'll be getting an adapter.

throttle bodies would be an off the shelf item, way too much R&D to do it yourself - and i would suspect that they would be CNC machined. try googling 'webber' or the likes.

I'll see if i can dig up Don's old thread...

[Eug]

http://www.skylinesaustralia.com/forums/Rb...24#entry2667024

found a workshop that will do my balancing and a tuner.

currently don't have time (not for another month at least). however i'll get them to assess my block and see if i will need a rebore on the RB30.

the verdict will determine what pistons i use, i'd like to use the ones in my current motor if they are in good nick. i'm aiming for 11:1 - which i hope is a good compromise. will then have to discuss with my tuner to determine what he thinks is appropriate, tunable and most importantly safe/reliable.

although i'm only doing the bottom end at this stage, what i choose will determine the head work. i.e. cam lift i can run, etc.

so cam regrind, compression and/or timing. they all affect one another - gay!

[screamin']

throttle bodies would be an off the shelf item, way too much R&D to do it yourself - and i would suspect that they would be CNC machined. try googling 'webber' or the likes.

I'm building some myself. Just stripping down the head. I'll be a rebuild on that, a bit of port work, then fabrication of the ITB setup.

Was meant to have all this done by now, but I keep putting dents in the rear guard of the damn thing!

[GTS4WD]

I'm building some myself. Just stripping down the head. I'll be a rebuild on that, a bit of port work, then fabrication of the ITB setup.

Was meant to have all this done by now, but I keep putting dents in the rear guard of the damn thing!

How are you doing this? Can we get some details?

Eug.. wht dont you work with what you know? If you are going to get cams re-grinded, you you will know how much lift you have.. this will determin the comp. ratio you can run.. and the timing will be based on the combination of both of these.. If you calculate all this and find out you want to have more advanced timing (although timing wouldnt realy net that much gain.. no point sacreficing cams for timing) you can get the cams re-grinded to a less agressive lobe.

http://www.torinocobra.com/Randys_tools.htm

Very helpful site..

If your doing the bottom end in one go.. have you thought about new rods?

And just a side note: When an NA car comes on aggressive cams hard its going rev out very very very quickly.. would a lightened flywheel be a smart idea?.. its going to rev out even quicker.. just a thought..

Edited April 29, 2008 by GTS4WD

[Eug]

i'm interested as well...

one of the main issues with the RB26 plenum/throttle body adapter is that it fouls some plugs on the intake side of the RB25 so some easy customization is easily done. however it is looking into a $1k+ exercise.

some off the shelf/self fabrication might turn out cheaper. adapt it to a forward facing plenum and voila

[GTS4WD]

Any ideas on whether it is a VVL or not further up the page? On post 83?

[Eug]

Any ideas on whether it is a VVL or not further up the page? On post 83?

need a pic from the intake side, near cylinder 1 - thats where the solenoid goes

[screamin']

I'm working on an ITB setup for my rallycar. It's going to be built on a 2ltr bottom end because the classes run by engine capacity and in my class 2000cc is the max.

We're just working with our cam guy to establish what the optimum angle for the TB's is and the angle that the air/fuel mixture meets the head/valve. Air speed and direction are key to this system working, so we're doing our homework on intake runner length and the flow of the system.

I'm just finishing off rebushing the rear subframe, then I'll be into the head/intake. I'll keep you posted with the progress.

[SKiT_R31]

And just a side note: When an NA car comes on aggressive cams hard its going rev out very very very quickly.. would a lightened flywheel be a smart idea?.. its going to rev out even quicker.. just a thought..

No way, remember - the engine is directly connected to the wheels, if its revving quicker, your moving quicker, which is kind of the whole point???

With my car, its a bit of a hand full in first and second - at about ~5000rpm+ the car just gets a double hit of power breaking traction in first (mmm sideways - limiter) (6.5" 215's stock rims) and heaps of pull in second, but in 3rd and up you definitely want it.

Also, if your getting any sort of reasonably cam, you'd want a decent balance anyway, and if your going to bother with balancing it, you may as well get it done properly, all bits included, and you wont have to worry about revving it too far.

to give an idea, on dons old engine as it was when i got it, peak torque hit at 5000rpm on the dot and peak power at 6000rpm, dropping off from there steadily until limiter. Thats with 2.25" exhaust and low end extractors, stock plenum.

Now, short inlet runners, fujitsumoto (however you spell it) big pipe mandrel extractor's, dumping into 3" straight through, an extra ~ 1 CR (into mid 11's) power builds at the same spot but hits much harder and seems to keep making power peaking past 6000rpm and doesn't fall at all by limiter.

and thats with the same mild 255 deg regrind, if you were to go a larger cam than that, she'd definitely want to be well balanced.

My cars in getting sprayed atm (could take a while, side job - going to be done properly) once its out, its going on the dyno to get a proper tune (on microtech ltx12s) with a full time water injector (pulse width) so i cant wait to see what the power curve looks like

Edited April 30, 2008 by SKiT_R31

[CeJay]

If this is going in the gts4, how you planning on getting it to fit under the bonnet? due to the extra height from the awd setup.

[GTS4WD]

If this is going in the gts4, how you planning on getting it to fit under the bonnet? due to the extra height from the awd setup.

See how much I can shave off the engine mounts. I realise that the front diff comes close to the cross member. But Im sure I can squeeze a couple of mm there.

see if I can put spacers to raise the bonnet 2 maby 3 mm.

Then.. shave/cut the bonnet rienforcements (the curved bulges that ru along the underside of the bonnet. And loose the under bonnet carpet thingy.

That there is at least 15-20mm.. if not more.

Bear in mind that the GTR bonnet closing issues is because the GTR bonnet leaves less clearance that a GTST. I just fitted a GTR bonnet and there is LESS clearance between the engine and the GTR bonnet than there is with a GTST.

this should be more than enough. But if things do get worse.. Ill experiment with a GTST and GTR bonnet which I have both of.

And if that is up to shit.. Fiberglass bonnets.

The only point where contact COULD happen between the engine and bonnet is in the corss pipe of the intake manifold.

Just my thoughts..

[Tony1981]

Is anyone doing the RB25/30 N/A Conversion with RB25DE N/A pistons, remembering hearing about this fellow with a 240z who used,

RB30E block, crank and rods, RB25DE N/A pistons and decked the block to get about 10.5:1 compression ratio - using the pistons to get a higher compression ratio as opposed to shaving 2mm of the head would be a better idea wouldnt it?

Has anyone gone down the RB25DE N/A piston route when building there RB25/30 N/A motor?