RB25DET - 3 Litre Conversion Completed?

[the_tonkau]

There is lots of interesting information flying about on the net on how to do this attractive conversion. Although appreciated as fascinating reading for some Skyline/RB enthusiasts that rebuild their engines in the "cyber space garage", for those of us that are trying to build an engine for the real world, opinions are just not accurate enough. I am looking for someone in Melbourne (preferably) who has actually completed a running conversion that would be willing to share information on the build. Like anything that has taken time and effort, any help will be renumerated in the appropriate currency of choice.

Cheers

Steve

[email protected]

[Sydneykid]

Hi Steve, we have now done 16 X RB30/25/26's. What is it that you want to know?

[Guilt-Toy]

Been driving mine for the last few months too.

[the_tonkau]

One sunny day at the springnats....

I have a S1 R33 rb25det and it’s spun a bearing on No5. (looks like oil surge/starvation caused by motorkhana action at the springnats) Have you seen this happen on the rb's ?

Anyway... in a nutshell, I need to know EXACTLY what needs to be done to use a 3L block with my head.

What vl block to use, na or turbo?

What forged pistons to use to keep compression close to the standard 9:1 ish

Does the rb25 oil pump/water pump swap across?

Manifolds swap across ok

Exact measurements of new holes for timing belt tensioner etc

vct issues

loom requirements/changes

exhaust mods needed

Water/oil gallery issues.......the list goes on....

Ideally I am after someone local I can sit down with and over a beer etc, have a look, discuss all the trials and tribulations they went through and the solutions they found. A checklist of what's needed would be great, I'm sure it would be worth a few dollars as well but as there is so many variables and differences between models it would be impossible to get right for every solution.

Now, after saying all that, I am still after as much info as i can and if you have experience in building these conversions I will very gladly accept any help you can give me.

The team consists of my engine builder brother who usually works on V8's and our good mate the chassis builder, who is normally building drag cars so my rb25 stripped to bits on their engine stand is a new toy for them to work out. The more accurate the info I can give the boys, the easier and cheaper it will be.

Thanks Sydneykid, appreciate the help.

Steve

[salival]

*taken from "cubes" signiature since I beleive it's a really helpfull guide*

http://www.geocities.com/r32_jjc/rb30det/d.../diyrb30det.zip

It contains a PDF explaining alot of stuff to do with the rb30 transplant, it does make for a viable option, though.. especially since you don't *need* to run forgies..

There's a guy in New Zealand (you know, baa baa sheep land) called RIPS on the skylines down under forum who makes the rb30 hybrid engines.. $3500 NZD for 2wd who's done quite alot of them.. he's running around with standard bottem end rb30's with rb25de heads with alot of success.. you may want to contact him.

[Sydneykid]

Hi Steve, suggestions follow your questions;

* I have a S1 R33 rb25det and it’s spun a bearing on No5. (looks like oil surge/starvation caused by motorkhana action at the springnats) Have you seen this happen on the rb's ?

Unusual, unless the oil level was low.

* Anyway... in a nutshell, I need to know EXACTLY what needs to be done to use a 3L block with my head.

Drill and tap the hole for cam belt tensioner, otherwise bolt it up the same as you would for a replacement RB25 bottom end.

*What vl block to use, na or turbo?

Doesn't really matter until you get over 650 bhp, then I always hand pick a block anyway.

* What forged pistons to use to keep compression close to the standard 9:1 ish

We use JE Pistons, there are other choices. You can use your standard RB25 psitons and adjust the compression ratio (down) with a thick head gasket if you want. You can use standard RB30E pistons, they give around 8.6 to one using a thin head gasketand depending on combustion chamber volume.

* Does the rb25 oil pump/water pump swap across?

Yes

* Manifolds swap across ok

Yes

* Exact measurements of new holes for timing belt tensioner etc

There is an accurate drawing on the RB30 thread

* vct issues

If you want to run the VVT, then simply drill and tap into the main oil gallery and use an external (braided if you like) hose from there to the VVT inlet gallery on the head. Once again the details are in the thread.

*loom requirements/changes

Zero, none, zilch, not one.... as long as you use the RB25DET sensors (ALL of them) and the ignitor, coils etc. SIMPLY everything that plugs into th standard wiring harness needs to be swapped over from the RB25 to the RB30 block.

* exhaust mods needed

Mine fitted up without any mods at all. It depends on the closeness of the engine pipe to the firewall, some designs are a tighter fit than others. Worst case I have seen was a 15 mm spacer bertween the dump pipe and the engine pipe (two bits of 6 mm plate with a gasket in between and longer bolts to join it all together).

*Water/oil gallery issues

Zero, zilch, none, not any ............

*......the list goes on....

Ask away.

*The team consists of my engine builder brother who usually works on V8's and our good mate the chassis builder, who is normally building drag cars so my rb25 stripped to bits on their engine stand is a new toy for them to work out. The more accurate the info I can give the boys, the easier and cheaper it will be.

Anyone with engine building experience could do the swap in 1 day. Honestly, what you HAVE to do is a lot simpler that what you might WANT to do. It all depends on how much power you are targetting. I did a 475 bhp swap over in 9 hours in my old garage with a minimum of home workshop tools (no machine shop stuff). I put the 2 engines on engine stands, side by side and simply swapped the bits over. The RB30E bottom end was rebuilt using standard VL Commondoor service parts as they were cheaper than the same parts from Nissan.

My best suggestion is it ISN"T hard, don't make it a bigger task than it really is.

[GTR32]

Hi Sydneykid;

That was THE simplest explanation I've seen. It's daunting for some of us to try and unravel the RB30 thread particularly when there seems to be a number of people having problems. Is it as straightforward for an RB26/30 conversion in a GTR and do accessories ir a/c etc bolt up? A couple of us down here are interested and have found the following:

the better shops want $20k for a 'complete / detailed ' conversion

we can't get a response from RIPS re crank girdles for a GTR to address a problem we've heard of often - block cracking in the RB26/30. We're assuming there is a problem in this area and that's why RIPS makes, as we understand it, a modified girdle

Is there any need to change gear ratios etc?

We'd appreciate any info you can send our way

Cheers

[Cubes]

It really is a simply bolt in procedure.

All the accessories, wiring, coolant, oil mate up with no problems.

There are only a few little modifications to be done which are very simple and can be done in your own shed with limited tools.

For the 4wd the only issue is the crank girdle.

Get that sorted and start the conversion.

Worry about the other little issues when you come to them, they really are stuff all. (Turbo oil lines requires a little bit of manipulation etc)

As SK said.. Don't make it a bigger task than it really is.

RIPS won't sell just the crank girdle. You will have to buy a complete motor.

[the_tonkau]

Thanks for the support lads. Not trying to make it harder than it is, its my daily driver and time is of the essence, the less delays while assembling the better.

*......the list goes on....

Ask away.

..OK

More q's SK if you dont mind mate.

# my current tune includes power fc/upgraded fuel pump/adj fuel reg/to4e/std injectors/4" exhaust/Large FMIC, 45mm pro gate.

-ac/ps/alt brackets all bolt up?

-water points on the block the same?

-If I use a vl na short motor with std pistons, at what rwkw do they start breaking?

-if putting in forgies, any machining needed to pistons due to 4 valve head?

-Advanatges keeping vct

-at what kw do the std injectors run out on the 3L(was running @high 80's @ 245rwkw with the 2.5L)

I know that some of the above q's are in the forum, but as you have actually built these things i would appreciate your ideas.

Thats it. What do you drink mate?

Steve

ANYONE IN MELBOURNE FINISHED ONE YET?

[riceline]

I'm in Brisbane

Have been driving mine for about 6 - 7 months now.

Still have a few things to do but its all add on mods (ecu, cooler etc)

[MonstaS4]

I'm in Ballarat. My RB30DET has been in my VL for only a month.

I'm using a standard N/A bottom end with an R33 VCT head. When using this head you DO need to modify the water gallery around the VCT oil feed as it only seals with about 1 or 2mm of material. You also need to drill and tap a hole in the head for a grub screw to block the VCT oil feed gallery (coming from the block). You then use an external feed as SK has already mentioned.

[the_tonkau]

I'm in Ballarat. My RB30DET has been in my VL for only a month.

Hi MonstaS4,

Dont suppose you took any pictures of the head mods you had to do? What pistons have you used? What's the drivability like off boost?

Cheers

Steve

[MonstaS4]

No pics sorry......have a look at Joel's (cubes) pdf guide. He has 2 pics in there, 1 of the RB25DET bottom end and 1 of the RB30 bottom end. The difference between the 2 is easy to see.

Pistons are stock N/A RB30, but the crowns have been ceramic coated.

Off boost??? What's that???Haha. No sh1t, i cannot notice any lag at all. I'm using a GT3040 with a 0.86 rear. On the initial dyno tune (with 20kms up) it made 162rwkw at 5000rpm @ 5psi, so can't wait to wind it up to 13-14psi.

[RIPS]

Hi,

The R33 style head will not bolt straight on but as described above, it is not a big deal to make it work with mods to the water and oil ports. The girdle I make is purely an adapter plate to enable us to run 4wd RB30's. For 2wd we have made 500rwhp with stock blocks, no problems. With 4wd and totally stock RB30e internals we make 600rwhp and run a 10.20 @ 134mph in a GTS4. Once you sort out the mods to the head (and a few other things which people have missed on this thread) it is a straight forward swap.........Rob

[Alf]

* What forged pistons to use to keep compression close to the standard 9:1 ish

We use JE Pistons, there are other choices.  You can use your standard RB25 psitons and adjust the compression ratio (down) with a thick head gasket if you want.  You can use standard RB30E pistons, they give around 8.6 to one using a thin head gasketand  depending on combustion chamber volume.

The thin head gasket, how thin was it and what brand was it if you dont mind saying.

[the_tonkau]

Monster,

Coupla Qick Q's Who Did You Head Mods?did You Buy The Pistons Coated?

Thanks For The Input Rips!

Steve

[MonstaS4]

Steve, M&W engines here in Ballarat done my head mods.

Pistons are the stock N/A RB30's. I sent them to www.jet-hot.com.au/ in Castlemaine to be coated. Cost around $20-$25 per piston from memory.

This coating will increase the risk of detonation as the combustion temps are held in the chamber, but the piston will run a lot cooler for the same reason. Only time will tell how they last!!

[Cubes]

MonstaS4,

They also increase power and thermal efficiency.

Have you thought about also ceramic coating the valves?

[Cubes]

MonstaS4,

When setting up the motor make sure you have a good quench. Around 0.040".

So that will require a zero deck height and a .040" (1mm) headgasket (stock).

You know what quench does, cools down hot spots that cause detonation.

Get the heads combustion chamber polished, cc'd and any sharp edges removed.

If you have done all that you should not have any more detonation problems than a non-ceramic untouched stock rb30det.

The quench is critical and should be basically around the mark anyhow.

[Sydneykid]

Hi Sydneykid;

That was THE simplest explanation I've seen. It's daunting for some of us to try and unravel the RB30 thread particularly when there seems to be a number of people having problems. Is it as straightforward for an RB26/30 conversion in a GTR and do accessories ir a/c etc bolt up? A couple of us down here are interested and have found the following:

the better shops want $20k for a 'complete / detailed ' conversion

we can't get a response from RIPS re crank girdles for a GTR to address a problem we've heard of often - block cracking in the RB26/30. We're assuming there is a problem in this area and that's why RIPS makes, as we understand it, a modified girdle

Is there any need to change gear ratios etc?

We'd appreciate any info you can send our way

Cheers

I have no idea what you mean by "block cracking in the RB26/30". I have seen split bores from too much boost and poor temperature control, but I have seen that in RB20/25/26's as well.

I have never used a crank girdle, I have seen one on a 1,300 bhp RB30 (it was 2wd), Nispro (and a couple of others) make them. They are needed when you are looking for more than 900 bhp. I don't believe it has anything to do with 4wd, more about block rigidity, which is always an issue on HUGE power straight sixes.

The adaptor for the 4wd sump is pretty much just two pieces of billet alloy that bolt up to the bottom of the RB30 (2wd) block and add the bolt pattern for the 4wd sump. They also have couple of strengtheners to handle the weight of the diff and the drive shafts. Our old race team fabricator made a set over 4 years (75,000ks) ago and that car is still running. Don't ask, he isn't around any more, so next time I have to use one, we will have to start from scratch.

Somebody asked about quench, I have found the standard Nissan RB26 quench to be the best. I have no evidence that anything else is better and we have tried a few.

Alf asked about the thin head gasket, we ALWAYS o'ring the block and we have head gaskets made to suite. RB30's have been around for so long that there are heaps of people who make big power stuff (like head gaskets).

Ceramic coating of the pistons crown works very well, but we only do it in conjunction with the valve heads, combustion chambers and exhaust ports. I have run an RB30 without block mounted oil squirters but with ceramic coating and it looks fine at its first pull down service. I can't find any differences in wear to the ones with oil squirters. Adding block mounted oil squirters to RB30 blocks is a real pain in the ass, so ceramic coating looks like a workable alternative.

So onto Steve's questions;

-ac/ps/alt brackets all bolt up?

Yes

-water points on the block the same?

Small difference, damn obvious to anyone with engine building experience. Put the blocks side by side and it sticks out like ......

-If I use a vl na short motor with std pistons, at what rwkw do they start breaking?

My rule of thumb is 475 bhp, others have achieved more.

-if putting in forgies, any machining needed to pistons due to 4 valve head?

Depends on the pistons you choose, the compression ratio you want and the camshaft lift you have. Generally speaking, no.

-Advanatges keeping vct

Same as for RB25DET, you can have small overlap at low rpm to improve power and larger over lap at high rpm to improve power. It really depends on the cams you use. For keeping with VVT, I like the Tomei Poncams 256 (non Neo) 260 (Neo), they work well with the standard valve springs, guides, retainers and hydraulic followers. If you are going ot use cams that don't work with VVT, need upgraded valve springs, guides, retainers and solid followers then I suggest an RB26 top end is a better (and cheaper) solution.

-at what kw do the std injectors run out on the 3L(was running @high 80's @ 245rwkw with the 2.5L)

I have never been able to get over 225 rwkw out of standard RB25DET (non Neo) injectors. Plus I have never built an RB30/25/26 with standard injectors. I have used the standard S14 SR20 480 cc injectors, they work very well with the standard RB30 bottom end (475 bhp) power limit.

-What do you drink mate?

Jack Daniels

Hope that answered the questions:cheers: