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Jamo's RB25DET ''250Z''


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Hey guys

 

After seeing the great work done on GAS RB26 installation, I thought I'd give you a few pics and insight into my lil mule.

 

It's a 73 240Z that had a turbo L series, now being replaced with an RB25DET.

 

I went with the 25 as I like them for the variable cam timing and inlet manifold. Many view the 26 as the one to have, and that's cool....it certainly looks the goods; but for driveability, I prefer long inlet runners and VVT along with ball bearing turbos to maximise response.

 

My engine is basically stock internals, but with a GT35/40 turbo (internally gated), Nismo 740cc injectors, APexi FC controller and the R33 twin synchro gearbox. I was a bit luck with the tail shaft as the front piece off the standard skyline fitted without modification (except for replacement of the diff flange with the skyline unit...they go straight on, altho I added an external slinger to stop dirt getting at the seal.

 

I removed the gearbox saddle from the body, and sectioned it as well as reconfiguring to suit the modified gearbox cross member from the skyline.

 

The car has also got power steering from a Subaru, so I retained the R33 P/S pump to serve the Subie rack.

 

Here are some pics

 

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And here are some of the saddle as it was being modified. The shot of the floor underside shows where the saddle was removed from the original position, and then moved back about 80mm. The area where the deadener is scraped away is about where the rearmost flange was re-welded to.

 

I only had to remove about 12mm from the top of the saddle and reweld to get the width right. The shape of the body matched exactly, so you can weld the saddle back in without having to massage it.

 

 

 

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Thanks guys..

 

Simon: ETA is another couple of months I reckon...I am away so much with work ATM (and deer hunting half the weekends!), that the progress has slowed a bit, but it's still getting there.

 

Peter: Yah...I agree...I worked at Gibsons during the Skyline era, and have a lot of respect for the RB26, but it is a race engine, and mine is a road car, so I want driveability over peak power. The RB30 combo is nice, but I just didn't think I needed that kind of torque, and it also was going to present a lot of packaging problems for the inlet manifold with the extra height, not to mention additional weight, so I decided the 25 is the right medicine for me.

 

Here is where the gearbox lever came out...the fact that this fore/aft location allowed the use of the standard R33 prop shaft was pure @rse!

 

Exhaust pipe is 3.5"stainless all the way, and sump is custom made, a direct copy of what I used to make for the RB20's in the old Gibson R31 'Peter Jackson' Skylines. About as much fun as making a set of headers!

 

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Nice work from a fellow RB25er and hunter.  I like your gearbox cross member, mine is a lot more simple and seems too small in comparison lol (yes still talking about the gearbox support :P).  Yeah, the RB25 puts out plenty of power for the zeds and with your combo, you could easily put out 250-300rwkw and quite safely.  Good work.

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Thanks for the comments guys!

 

Scott: It's not the size of your cross member that counts....it's the stiffness!!! Mine was adapted from the standard R33 skyline mount...it was a bit of fiddling to shorten it, and then I added a closing plate to the bottom to reinforce the weld points. It's very stiff, and will allow plenty of rigidity for the rubber isolator to work against.

 

Kato: Thanks for the comments....I am happy with how it's going, and when all the plating is finished, the engine bay should look sweet!

 

Power wise...I am after about 500 engine HP....so we'll see how we go in achieving that....it's not all that important in truth...it will have heaps of power for what it is....bring it on!

 

Jamo

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  • 2 months later...

Hey guys

 

I had a bit of a diversion during the re-power, which was to clean up the underside of the car to complement the new engine. Thanks to KatoKid of the use of the rotisserie, which made the job a thousand times easier!

 

First shot is of the underside before clean up, but after pressure wash

 

 

Second shot is the underside after stoneguard

 

 

Final shot is the underside after final paint

 

 

 

Cheers

 

 

Jamo

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Ha! Yes, it was a bit of messing around, and stripping old deadener off is a pig of a job....but, it is fantastic to work on now, as it is clean from end to end. This is the last time I am pulling it apart to do this, so I figured I'd do it right. Next car is going to have a 426 Hemi in it, so when I start that, I don't want to be thinking I didn't give the Datto my full attention!

 

Cheers

 

Jamo

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Ok...status update:

 

- Cylinder head went back together today, so it's fully reconditioned and ready to go....Orger's still do exquisite machining!

- Frt x-member finished, with the LCA bolt holes moved 12mm outward and 25mm up. That puts the centres right on the same plane as the inner steering arm ball joints, so minimal bump steer. All the rest of the power steering installation is done now, so it's just a coat of paint for the x-member and put the whole lot back in the car.

 

I am on to the engine oil pan now, and have about 12 hours work left in it I reckon and then it's off to the platers.

 

Does anyone have any bright ideas on the speedo output from the gearbox...it currently has a speed sensor in it which the ECU uses to determine road speed and make decisions about whether to run the fuel pumps and idle speed adjustments. BUT, I need to have a cable drive to the car speedo as well...what to do??

 

What have other RB25 installers done about this dilemna?

 

Cheers

 

Jamo

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I used a VDO speedo to replace the original.  They are very plain and standard looking and so look the part, but are good quality and accurate.  They use the standard RB25 speed sensor to read, so not a bad way to go.

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Interesting possibility SCO....I want the car to look original though, so might see if Ringwood speedo service could graft the VDO internals into the 240z speedo assembly...might be possible.

 

The standard speedo is god-awful anyway...ok when you're at a steady speed, but accelearting or braking it tends to overshoot.

 

Cheers

 

Jamo

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I am on to the engine oil pan now, and have about 12 hours work left in it I reckon and then it's off to the platers.

 

What are you planning on plating it with? Chrome, zinc, gal?

 

I would recommend not plating it as it can flake off and be lodged inside the sump. Just paint or powdercoat the external parts as the inside will have oil in it anyways so it won't rust.

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Hey Handsandwich

 

I will zinc plate it, with a gold finish. I could paint it (outside only), but i like the gold finish...it's how we used to do the race pans at Gibsons.

 

I have never had a problem with the finish flaking off if it's been done right.

 

CHeers

 

Jamo

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999 165 002 Is the only part number I could find.  VDO Kienzle, its the 200km/h version and I think 80mm diameter (whatever fits the zed).  But its close to 5 years old.  I just had a look at the VDO website and they have similar looking ones on there.

Side note:  When I got a price for it, I remember to go from the 200km/h to the 300km/h version was about $700 difference!!

 

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