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RB25DE into 240Z Conversion.


Zedman240®

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Just thought if anyone else is thinking of going the RB series engine direction, a few pictures and info of whats to be done and what you need. First thing that comes to mind is the sump! If you are thinking seriously about the conversion, find and grab hold of a RB20 200ZR sump! Or second best a Patrol GQ (RB30) sump which will have to be modified and oil pickup! Nissan in Brighton say they are no longer available or what may be the easiest, just modify the existing sump. I tend to go with the one that involves the least stuffing around. I've already found a RB25 motor, and started removing all useless original items....like plenum chamber etc..

First pic is when I brought it home, then after the "diet"....

 

More stuff to follow!

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I am going RB on my 260z 2 seater (long term custom project). I have picked up the following items.

 

1 x RB30e

1 x RB26 head (minus manifolds)

1 x LINK ECU (NZ Made see www.linkecu.com)

1 x RB20DET box

1 x RB20DET sump from a 200ZR (new imported from the US) and pickup

1 x Castle Main Rod Shop mounts (imported to NZ via a business trip to Melbourne)

1 x Set of H-Beam rods for the RB30 bottom end

1 x ARP main studs set (RB30)

1 x ARP head studs set (RB26)

1 x Tomie 1.0mm metal head set (RB26)

1 x Triple EFI Hardware DCOE throttle bodies tapper bore 50/48/45mm

 

However I have now picked up an engine that I can put in the car while I get this RB30/RB26 hybrid finished. I will be doing NA not turbo as this is what I want to do.

 

So here are the details on the engine I picked up to get the car back on the road while I build the above.

RB25 Block, RB26 head, Tomie 1.0mm metal head gasket, Top Secret tuned ECU, Stainless Steel headers (need to be cleaned), HKS high lift cams and HKS adjustable cam gears. In the weekend I dropped the pants to swap over to the ZR sump and the rods are stock Nissan units with a lot of work, ie lightened, shot penned, etc Pistons (looking from the bottom) are near new units. This engine came with a RB20DET box fitted with a quick shifter. I have not removed the box yet to see what clutch setup is in there but given the other work done I can only assume a good twin plate.

 

I should have this engine installed in the car by next weekend so my panel beater can check things over before finishing up the body work/engine bay.

 

So there you go I will be installing a RB25DE sort of well RB26DE too (not sure of the crank and rods in the RB25 block - does anyone know the partnumbers and were I can find these looking from the bottom without pulling the engine apart. I know L6 and can tell a L24/L26/L28/LD28 crank but looking for the partnumber cast on the crank but I have no idea on the RB's). Then later I will be upgrading to RB30DE with my RB30E and RB26 head :)

 

I have attached some pics of the new 25/26 hybrid engine as I delivered it to the panel shop a few weeks ago - I will get some more now it is sitting on a cross member with the ZR sump on (sump will come off again before going into the car as I forgot to take the Nissan gasket/sealer with me in the weekend)

 

Sorry for the long post - also I will install the EFI Hardware Triples and the LINKECU on this 25/26 engine.

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Hey Nzeder, looks like you are going to finish the intake manifold for the throttle bodies before me; would love to see how you are going to tackle that one. I was thinking of cutting the original manifold down the seam near where it mounts to the head and weld on weber shaped plates. I'm still waiting on the ZR sump from the US. Thanks to Lurch, Butch at Courtesy Nissan in Texas is sending it asap! Still waiting on the Castlemain Rod Shop mounts as well.

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The RB26 heads came with triple TB's remember however they are not a DCOE bolt spacing very close but not quite the same. With the RB26 head I got (I actually purchased a RB26 engine just minus the turbo manifolds and the plenum/TB's) the little manifold that the standard TB's bolt to so that will make things easy for me. Also the other engine has the plenum and TB's  ;D

 

I plan to make some adapter plates to change the bolt spacing from RB TB's to DCOE so I can mount up the EFI Hardware TB's. The bore spacing of the RB TB's is almost the same so close it is not funny so the adapters will also be ported to match this too. I will be using bungs to block off the standard injector holes in this manifold (ie no injectors by the head) and use the injectors by the TB's plates on the DCOE TB's

 

I will take some pics later to show the difference between the DCOE mounting and the standard RB26 TB mountings.

 

EDIT:RE the CMRS (Castle Main Rod Shop) mounts I have modified mine to take a different mount not the standard Z mount. I am going to be using a Energy Suspension universal mount for a Jeep. Why? Well these mounts are captive ie if the fail they have an interlock design so the engine will not leap around. I chose these mounts/isolators as they are:

1. Captive

2. A firm rubber/compond is used

3. Are the same hight as the stock isolator/mount

4. Easy and cheap to replace $23 USD vs $70 USD for the stock Nissan

 

With the mod to the CMRS mounts my engine will now sit 5mm taller than if I was using the their unmodified mount. I weled on another 5mm plate to extend the mount to pickup on the wider isolators ears. This plate has been mig welded and mig plugged I will know later if the engineer is happy with this.

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Ok just popped out to the garage and took some very quick pics - I did not un wrap my RB26 manifold but this does give you an idea on the differences.

 

1. The RB TB mounting has the same bore and bolt locations but from the left and right they are just rotated around - you should see this in the pics.

2. It should not be too difficult to make a bolt on adapter going by the look.

3. I recall seeing an old Alfa or like which had an adapter that did just this - I will make a template out of MDF or the like and visit the local weber guy that I know that has one of these Alfa adapters and see if they are the same.

4. If the Alfa adapter is different I will take the MDF sample to an engineer/CNC to get some made up.

 

 

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got access to a scanner???

scan the flange with a steel ruler laying flat and email the pics.....

or take square on photos with again a steel rule across the face for ref dimensions.

 

could have something drawn up in a matter of an hour that you can print 1:1 and check on paper before you send the dxf/ dwg files to the cnc shop.

 

email is a beautiful thing, as i am aware you are in NZ.

 

make sure you have photos of each side, ie 1 pic of the mate & 1 pic of the matee'

 

nato 

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Cheers Nato, I will get into the roof and get my RB26 head gasket set down as this will be easier to scan than the little manifold, I will then also scan the DCOE flange again as you have stated both with a metal ruler next to them :)

 

I will do this in the next day or so. PM me your email address and I will send you the files as scanned, I will make smaller for posting on the site for others to reference.

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Heres something I want to end up looking similar to if all goes well. Going to do alot of measuring tonight and trial fitting. Nzeder, do those headers you have on the motor fit in the zed? Are they the Coby made ones? That's one more detail I have to chase up!

post-801-144023486184_thumb.jpg

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Nzeder, do those headers you have on the motor fit in the zed?

Not sure yet this is one of the reasons for getting the engine installed before the engine bay is painted incase we need to alter things a little - be it the floor or the headers

Are they the Coby made ones?

Hell no Coby units are much much shorter and not made from Stainless Steel. These are a quality Japanese made unit they look like the Fujitsubo SuperEx see

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these claim to add 10HP to a standard RB25DE, these have be modified to suite the RB26 head as these have a different exhaust flange. And cost ¥165,900 which is $1700 AUD without shipping or local taxes this is one of the reason for purchasing this engine + and having another RB26 head is a good thing. Let just say I got the engine are the right price when you add up the parts.

 

The Coby ones are like this (however this is the only pic I could find on the internet quicky, and is for the RB30E ie single cam, but the pipe length etc is the same design = not long enough for good performance up high in the RPM range)

20839221.jpg

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Stop it! you guys are sooo tempting me to do an RB conversion on my Z.

 

Naughty Naughty Naughty!

 

Must block unclean thoughts :).

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Stop it! you guys are sooo tempting me to do an RB conversion on my Z.

 

Naughty Naughty Naughty!

 

Must block unclean thoughts :).

Gav you can't do it given I sold you my L14 rods given they are hens teeth you just must use these in a good L6  8)
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Stop it! you guys are sooo tempting me to do an RB conversion on my Z.

 

Naughty Naughty Naughty!

 

Must block unclean thoughts :).

Gav you can't do it given I sold you my L14 rods given they are hens teeth you just must use these in a good L6  8)

 

True I mustn't loose sight of the end goal. To build a 300HP N/A L6 :).

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im happy with my rb20det  ;D. approx 11L/100km and still heaps of power to suprise the latest and greatest in V8 and turbo form and this is still in untuned form.

 

has a great sound maybe the lenght of the pipes or something.sound bit different than ur average skyline.

 

never looked back on the L26

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Me I am not sure what to expect as my last 240z was a large, well they don't come much larger, L28 N42/N42 stroker built with forged cosworth pistons, OER 47mm carbs (new that I put on to replace the Weber 48mm, Japanese car must have Japanese Carbs right?), a Kakimoto header (again that I put on to replace the old locally made unit) and L14 rods. It was putting down close to 250HP on race gas, and with another head that I had built which had a much smaller cam (but well built ports etc), lots of work to get the compression ratio down to 10.5:1 so it would run on pump gas and it only dropped 20 odd HP so that was excellent on pump gas and such a small 230/230 cam. All that was on the same hub based dyno.

 

Here is a pic of the engine bay of the 240z but I am now looking forward to the RB project to see how well it will go in N/A form with the Japanese engine then later with the RB30/26 that we will get stuck into.

post-104-144023486431_thumb.jpg

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im happy with my rb20det  ;D. approx 11L/100km and still heaps of power to suprise the latest and greatest in V8 and turbo form and this is still in untuned form.

 

has a great sound maybe the lenght of the pipes or something.sound bit different than ur average skyline.

 

never looked back on the L26

 

 

BULK, it sounds just like a slykline!!!

was at the lights the other week, hear this "skyline" sounding thing launch it hard, was in between a few trucks etc, turn my head and who do i see???

you!!!!

 

So id say almost exactly like a skyline, maybe its the MASSIVE hot dog  ON THE BACK OF YOUR CAR, SORRY AM I SHOUTING, WAS THAT YOUR EXHAUST I THINK I CAN HEAR???

hahaha yes your car is loud when right foot sung throught the floor!!! lol

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nato i think u still may have some stuff stuck in your ears from the bike crash.  :P get it checked out. since u cant hear properly  ;D

 

it has hint of skyline but not ur typical skyline sound. one the mates has a r32 and sounds noticable different expecialy idle and at full bore,only common RB sound is the turbo sucking. now is it beause of the muffler or resonator i dont know. Yeah but it is loud when the foot is pressed hard down wont argue with that one ;D

 

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Talking of sounds here are some of RB??D and RB??DE cars in Japan. The first one is a C10 Skyline originally just a GT with L20a Engine now with RB engine running triple carbs

Now the same car but this time upgraded to tripe DCOE throttle bodies

 

Now the RockyAuto build S30 with RB power with triple DCOE carbs.

 

I have somewhere a copy of Skyline (C10) with a 3.1L L28 running a stainless steel exhaust system and I must say they sound almost the same as the Skyline above with the RB in it. The sound might have a lot to do with the use of Stainless Steel, remember that most RB turbo on the road usually have an aftermarket manifold made from stainless so does this make the so call RB sounds?

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Ok this is what I have been up to tonight  8)

 

The question about the header and would they fit ? The answer is almost they are fowling on the flange at the floor but only just. You see the engine mounts have been modified for the captive engine mounts and this has raised the engine 5mm from the standard castle main mount. So if this was not done I believe there would be no issues. Having said that I plan to install the RB30 in the future so that will lift the head 38mm from where it sits now so I am going to see if I can get the header modified to lower the flange.

 

Anyway here are some pics.

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Would the RB25DE sit in that same position? I'm hoping that because I would'nt mind having some extra room on the driver's side for the TB's. Last thing I need is for the TB's to just touch the master cylinder or something...

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I assume so given the bottom end is a RB25DE block. I just been looking at a number of pics of RB installed in 240z/260z look to see if others have their engines in the same location. Trying to find pics of other RB installs with the Castle Main Rod shop mounts but most are US installs and they have the steering wheel on the other side and the all seem to have the engine lean over more to our passenger side. So then I was looking for other OZ/NZ installs to see what they look like. I will know more about the TB room in a week or so when I remove the stock 26 stuff and installing my DCOE setup (once I get that complete but for the test install/fit it just might be a mock up)

 

Also if the moderator want to move my post to the members projects please do so.

 

EDIT: attached pic might give you a better idea on the room on the intake side.

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