Rb25/30 Na High Comp Build Up

[Eug]

good luck with it!!

[HR31GTS-X]

With a set of forged rods or getting the stock ones shot peened, how far can the RB30 rev? how far past 7000rpm??? If I spent $750 on a set of rods and bolts for an N/A application I would want to be able to rev its a@s off all day everyday :-)!!!

I don't think its necessarily so much the rods that limit the rpm, when it comes to rb30 blocks i have read that they experience harmonic issues at around 7500 RPM because the block simply wasn't designed for that RPM and doesn't have the strength to brace those vibrations.

You can do whatever you want with the rods but if you want to see high RPM i think you would have to fork out for an RB26 N1 block.

Anyway thats just my 2cents

[Cubes]

Much more than 7k you need rods AND an ATI balancer if you want it to hold together.

Its really just like the RB26 and RB25 at 7.5k+ and lots of track work. If you want it to hold together you must throw an ATI balancer at it.

Balancer and rods and 8-8.5k is not a problem. The VLT's back when I owned one were doing it back in their day. Tried and proven if you like.

Regardless how many rev's do you want. 8-8.5k is more than enough especially from the 3ltr. A turbo to suit such airflow requirements is pushing 1000hp. N/A its a different story.

Possibly a 26 is a better bet. ATI balancer, rods and pistons big cams and aim for 10k.

[GTS4WD]

Build has been put on hold due to the f*cker that hit and ran me.

[Silhouette-R]

I have just recently had a 26/30 built up n/a and here are some answers that your chasing are as follows and some prices

Crank:

- If your running the 30 bottom end you'll have a RB30 crank no doubt, now with the RB30 crank there are little plugs in the crank from where holes get drilled through it so these HAVE to be removed if your revving the motor past 6000rpm (have a tendency to fly out, not good!) and have them replaced with grub screws and get them knocked into place with like a centre punch so they definitely won't come out.

- You'll also need a crank collar ($165) if you upgrade the oil pump (I think it is if you replace the oil pump), i'm running a GTS-T oil pump which is more than enough cause the GT-R pumps will give to much pressure for a n/a setup due to the fact that the GT-R's have piston squirters and turbo's.

Rods:

- True the RB30 rods can withstand 250+rwkw (way more power than what you'll see out of a n/a 30) but the thing is taking them past there breaking point and it may only require 50rwkw at 8000rpm and twang there goes a rod so rods are a good idea also, I don't have rods yet and it doesn't mind being taken out to 7000rpm every now again.

Block:

- I'm using 30 rods with 25DE pistons, the block was chopped 50 thou (don't know how many mm that is) and the head was taken back a bit and I think the pistons had some meat taken off them as well from memory, if you want more accurate measurements I can contact people that put the motor together, either way it runs over 12:1 and under 12.5:1 CR. Very Nice!

All the machine work cost a bit under $2G and there is still more to go.

If your not keen on spending a lot of money straight up, then I wouldn't bother with cams and gears at this point in time unless you can get a sweet deal on either items, but seeing as how you have a non-turbo head everything to do with the cams will suit the n/a application.

Unlike myself everything is operating in turbo mode (f***ing annoying), will be getting gears first to dial the cams in a bit better then i'll throw some sticks at it. Hopefully it'll see the 230rwhp mark.

[25GTV]

Im building my na rb30de for my r34 soon. I plan to run it as stock as possible with an safc to add the extra fuel. Just wondering if anyone can answer some questions.

1.Will the rb25de pistons fit or must i bore it out?

2.what compression will i have by changing to the 25de pistons?

3.to use my original rb25de oil pump will i need a collar?

4.I plan on tappin into the oil pressure sender and plumbing the vct (how is this done?)

5.Do i need to change to a different oil restrictor?

6.What must i do to the head face to bolt it onto the rb30?

7.Is there any extra oil plum bing for the rb25de head?

Thanks

[Silhouette-R]

1.) The 25DE pistons will fit without boring (I'm using 25DE pistons)

2.) Don't know what compression you'll have but it'll be far too low for what you need, so you'll have to get the block machined.

3. ) I think you do need to run a crank collar

4.) don't know??

5.) I'm using oil restrictors but you they're not completely necessary but nice to have

6.) do you mean machine the head? or the tensioners?

7.) don't know?

[25GTV]

I mean the mating surface of the head, must i modify any oil galleries or water jackets? Im only aiming for 10.5-1 comp...

[Silhouette-R]

I don't know about that either, but there has been some people on here that have done the twin cam conversion with that head so you should have a look around and ask some that have done it to see what they did or get a 26 head

[...Joshwa]

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?

Lower piston crowns also produce less torque as the piston crown is closer to the crank so you lose leverage on the crank. Nm = force x distance. .

If I were you id look into getting a flat top hyper-eutectic piston made with a deck height of 0. . You can get them custom made with valve notches and to suit the bore size. . its around $900 I think. . (comes with rings, pins etc)

[GTS4WD]

I mean the mating surface of the head, must i modify any oil galleries or water jackets? Im only aiming for 10.5-1 comp...

All galleries and jacket line up.

You will have to machine the suface of the head to ensure its flat.

If you have a warped head it will cause problems with a good seal and could run into head gasket problems down the road.

[...Joshwa]

I looked into getting custom cams made at SureCams. . He quoted me 770 but I cannot remember if that was for both or just one :S ill give him call back. .

Just wondering what an ideal lift and duration would be. . I was thinking around 270 duration and 9mm lift. . ?

Im using a custom made set of pistons and aiming for 11:1 comp ratio, so keep that in mind

[GTS4WD]

Man.. Everytime this thread pops up it makes me sad thinking how much money I have to spend on stupid things like uni and how much of that I could be spending on the car..

[...Joshwa]

Ok,

Update on my build

My cams have arrived, intake 10.7mm 264deg, exhaust 10.2mm 270deg. .

Bad news is that one out of three of the oil gallery bolt holes (on the corner of the head) has snapped off. . so I have to get it all welded up and drilled. .

I have ordered pistons, custom forged dome topped pistons.. Good thing about this is that when it comes time for a turbo, I dont have to touch the bottom end for it to hold big power (400rwkw), as rods and pistons are forged and fully balanced

Thats about it for now. . Oh and I took a slapped it together just to see how it would look, kind of

[GTRsean]

Any of you guys seen the specs on this bad boy??

Change engine RB30E

RB26DETTヘッド改 Kai head RB26DETT

カム IN EX 共に300度 ポート加工 HKSスライドカムスプロケ IN EX cam with 300 degrees port processing HKS SURAIDOKAMUSUPUROKE

RB26用6連スロットル改 RB26 for improved throttle for 6

スポーツインジェクション SUPOTSUINJEKUSHON

等長ステンタコ足 Isometric leg SUTENTAKO

FコンVプロ Pro Con V F

R33樹脂製燃料タンク R33 plastic fuel tank

オプティマバッテリー(リア) OPUTIMABATTERI (rear)

Z32ラジエータ Z32 radiator

RB30 block

RB26DETT head, prepped and ported

300 degree inlet and exhaust cams

six throttlebody intake with trumpets (sports injection)

HKS F CON V pro computer, (map sensor based)

And 380 HP at the crank.

[Lithium]

Thats awesome, where did you find that?

[bomb3r]

That Looks like one of the rocky Auto 240's..

they do a lot of NA Rb engines.

[bomb3r]

click it:

www.rockyauto.co.jp/