240z Rb25det - Engine Build-up

[R31Nismoid]

If it was my car, i wouldnt bother building the motor, just run it with the gear you have and see what you like and dont like.

Agreed!

Mate of mine down here has a 240z with around 230rwkw, RB25 gearbox etc, it's a very fast car due to the massive weight savings.

Tad more power would be fine but otherwise it's just not required and you'll spend more time shredding tyres than going anywhere

IMO stick with 260-280rwkw, use a GT3071 and it'll have power everywhere and won't require you to bust the motor open and spend another fortune there.

The amount of money saved as opposed to chasing 300-330rwkw is huge, as is the response gains you'll get from going a slightly smaller turbo

[discopotato03]

I know someone from here once spoke of building an NA RB26/30 up and plonking into a Zed with high comp pistons and healthy cams . My memory is vague but I think an early factory 240Z weighed in at or a little under 1000 Kg ?

Yeah the nose of a Zed is quite long I think in relation to the strut towers and the engine sits a fair way ahead of the effective front axle center line . I think the rally peeps weld braces from the towers down towards the front of the rails but theres no real opportunity to triangulate things . Same deal as 6 cyl LC/LJ Toranas .

A .

[Dale FZ1]

I tend to agree with Adrian's comments. Spend $$ to obtain/maintain chassis integrity first.

Seeing Richard Galley's Z car at Rally Queensland, they can/do carry good speed.

Power:weight is where you'll get the performance, and recognising the much lower weight factor should help identify areas where the spending can be contained. L series can be made to go, but it's going to cost so I'd go with the modern engine combination.

You'll hit the power ceiling easily with a GT3071, but use a 0.82 turbine housing so it can continue to rev. I'd think you could target usable power from 3500-7500 without really doing much/anything to the head. Perhaps valve springs and a tidy up, run stock cams.

Bottom end, find some RB26 rods with decent bolts, forged pistons, and put the crank in for weight reduction. That would be what makes the whole package rev quickly and give some extra reliability. Yes I can see it will cost, but it would also make the package come together nicely with a 4.6:1 rear end.

[wolverine]

I'm not one of the experts but if you've only a got a 240Z shell to push around then you'd want a nice linear midrange with 550 to 600Nm max coming in as early as possible. The GT3040 adds more lag for no gain on a stock internal engine. I'd swap it straight-up for a GT3076 w/0.82 rear (normal GT30), run 17 or 18psi coming on full at under 4000rpm and be happy. The GT3040 adds more lag for no gain on a stock internal engine. I'd swap it straight-up for a GT3076 w/0.82 rear (normal GT30), run 17 or 18psi coming on full at under 4000rpm and be happy.

My standard R33 has a externally gated GT3040 from GCG and it makes 18psi comfortably before 4000rpm, the delivery is linear. (0.82 turbine housing)

I am not disagreeing that if Bryce was buying today go for a GT3071 or GT3076 but given that he already has a GT3040 sitting there it seems worthwhile to bolt it on and see how it feels. There is a probably a loss in response due to the larger comp wheel size but geez if I was carrying around 300kg less in my car it would be hard to notice.

[GTScotT]

A 240 with that kind of power... Someone has a wangan fettish

+1 vote for throw it all together and see what youve got Dont want to go buying new turbos and parts etc etc if your not even sure how your current setup suits your wants/needs. If its not what you wanted, you will atleast have an idea what characteristics you want to change and the relevant data on where to start.

[discopotato03]

I reckon just a good tight std RB25DET , maybe a Neo if available , and a 2835 Pro S with the 0.68 turbine housing should work well . A bit more exy but its a bit hit and miss with those 3071Rs and the full sized GT30 turbine . For whatever reasons that cropped turbine and the HKS turbine housing seem to work a bit better over a wider range and the ported comp housing takes care of any surge .

Cheaper and easier would be an RB spec GTRS turbo .

I'd be ditching the 4.6 diff in a car that light and opt for a 3.9 or even a 3.7 ratio final drive . These are still around in the type of long nose R200 that fits under the bum of those early Zeds .

A good RB25 should make more torque down low than a carburetted L24 or L26 so all good .

Yeah , tight Neo 25 with a GTRS would easily be quick enough on the street and very easy to live with as a daily .

With Stuarts steering and suspension bits you could make a very impressive classic that could embarrass many a current lump and hold its own steering/handling/braking wise .

A bonzai engine is expensive where a more conservative and budget conscious one leaves money to make an old car THE complete package . Nicer to drive and easier to sell for good money if you get tired of it .

A .

[Brycey]

holy cow, i haven't been able to get onto the site all week because of some "IPS Error" or something, but thanks for the massive response! i'm not really sure where to begin, ill have a good read when i get home from work, but heres an older picture of the engine bay for the moment..

Edited September 3, 2010 by Brycey

[STATUS]

Run a z32 you will like your car a whole lot more (300-350rwkw capable easy), the Q45 can be a real mole to tune out low speed fuelling issues as it just doesnt have the resolution.

[Brycey]

ok!! just to answer to a few of you guys, but thanks all the same for everyones thoughts and advice!

Std internals + GT3040 is usually a mis-match. What A/R is the turbine housing?

What are your expectations? What is your mid-range goal? Peak power goal? Do you want a monster or something genuinely quick and more usable?

I'm not one of the experts but if you've only a got a 240Z shell to push around then you'd want a nice linear midrange with 550 to 600Nm max coming in as early as possible. The GT3040 adds more lag for no gain on a stock internal engine. I'd swap it straight-up for a GT3076 w/0.82 rear (normal GT30), run 17 or 18psi coming on full at under 4000rpm and be happy. Will the chassis benefit from much more than 260-270rwkw?

Assuming you are ~1200kg then a RB25 would already behave like a 3.0L in a R33/R34, just with more revs and power up top. 550Nm in 1200kg is like 640Nm in a GTST! Having even more torque on that light rear end sounds like a recipe for no traction and slower speeds.

it may sounds silly but im 90% sure i went the 0.82.. im not 100% sure because it's been a while and it was a close pick between them as i was undecided which direction i wanted to take at the time..

good point about the 3.0L! factoring in the power to weight always slips my mind

thats awesome that is pretty much the exact same setup im in the process of building , but in r33, i would much rather a 240.

i went a .63 rear housing on the 30/40 as i am looking for responce in the long run

I'm sure we'll be able to compare notes down the line!

I agree, get it running as is. Heaps of stock RB25s making big power. Keep the money if you do have troubles one day and then build it if it breaks.

Awesome project BTW!

cheers mate, it's a good point to keep it as is (and im happy to hear it so i can get out of it cheaper!) but i cant help but having nightmares of the engine blowing up and sending metal shards through the entire oil system.. do it once do i right is what i keep telling myself with this project

Now lets see , a hotted up RB25 in an early 70's 240Z . Before you go gangbusters have a think about what a 240Z Datsun is and its steering/suspension/braking limitations . Actually I strongly suggest you speak to Stewart Wilkins because he has had a long term interest in those cars mainly from a rallying perspective . I have seen many big dollar tear down to bare metal 240/260Z builds there and I wouldn't think there would be much he couldn't tell you about these old cars .

They start out with a very long structurally unsupported nose but a least they had rack and pinion steering unlike many cars of the era . They do have problems with bump steer and Stewart has had many custom parts made to fix most of the front end woes in Zeds .

ek think hes even had custom hubs made to take 5 x 114.3 stud pattern wheels , and CV/pod joint style rear axle shafts to replace the archaic uni and ball/splined std ones . They can do the conversion work with custom bits to fit GTR Skyline brakes too .

I'm pretty sure they told me that Zeds really need a good welded in roll cage to get a reasonably stiff shell because std and at nearly 40 yrs old they move around like a cock in a sock .

I have seen pics of aluminium radiators and suitable intercoolers in the nose of a Zed but you don't have as much room as you would have in an R32 or 33 .

You obviously have a project in mind but in a way its a shame not to se a well built L28 under the lid of a real Zed and the triple 45s always created the essential growl in a hot 240/260 .

Cheers A .

Stewart sounds like the man to talk to!

i've tried to do this project as a pretty well rounded job. alot of attention has been spent on brakes, stearing, driveline, suspension - but not so much anythign to do with body or stiffening as thats the next stage. i wanted to get all the running gear completed so i wasnt too precious about bumping the car through the process - which has worked well! once i get some direction happening with the actual engine build then the bodywork will run along side. i have a pretty clear idea how to go about it but would love to talk to a few more people to get the seasoned tips..

its funny you mention the L28, a few years back i had a 280zx as my daily driver, the engine eventually blew up (yes i blew up the indestructible engine.... due to my negligence..) and did a ground up restoration, came out a charm! the L series is magic one say id loveto go the distance with an L24.. but that'll be a while away!

i still have my L28 block sitting back at home with a large welt in the side from throwing a big end.. should buff out

Agreed!

Mate of mine down here has a 240z with around 230rwkw, RB25 gearbox etc, it's a very fast car due to the massive weight savings.

Tad more power would be fine but otherwise it's just not required and you'll spend more time shredding tyres than going anywhere

IMO stick with 260-280rwkw, use a GT3071 and it'll have power everywhere and won't require you to bust the motor open and spend another fortune there.

The amount of money saved as opposed to chasing 300-330rwkw is huge, as is the response gains you'll get from going a slightly smaller turbo

yeah very much understood, and even if i was to reach around the 260-280 mark i'd be silently happy.. i still can't help but wanting to do some internal work.. just to be safe and create a more rounded project..

I know someone from here once spoke of building an NA RB26/30 up and plonking into a Zed with high comp pistons and healthy cams . My memory is vague but I think an early factory 240Z weighed in at or a little under 1000 Kg ?

Yeah the nose of a Zed is quite long I think in relation to the strut towers and the engine sits a fair way ahead of the effective front axle center line . I think the rally peeps weld braces from the towers down towards the front of the rails but theres no real opportunity to triangulate things . Same deal as 6 cyl LC/LJ Toranas .

A .

yeah the 240's weigh around 1080kg standard.. there are a few different numbers thrown around on the net but its all within the same ballpark - very light!

no doubt that stiffening is essential..

I tend to agree with Adrian's comments. Spend $$ to obtain/maintain chassis integrity first.

Seeing Richard Galley's Z car at Rally Queensland, they can/do carry good speed.

Power:weight is where you'll get the performance, and recognising the much lower weight factor should help identify areas where the spending can be contained. L series can be made to go, but it's going to cost so I'd go with the modern engine combination.

You'll hit the power ceiling easily with a GT3071, but use a 0.82 turbine housing so it can continue to rev. I'd think you could target usable power from 3500-7500 without really doing much/anything to the head. Perhaps valve springs and a tidy up, run stock cams.

Bottom end, find some RB26 rods with decent bolts, forged pistons, and put the crank in for weight reduction. That would be what makes the whole package rev quickly and give some extra reliability. Yes I can see it will cost, but it would also make the package come together nicely with a 4.6:1 rear end.

that's some helpful info mate, cheers for that :-)

My standard R33 has a externally gated GT3040 from GCG and it makes 18psi comfortably before 4000rpm, the delivery is linear. (0.82 turbine housing)

I am not disagreeing that if Bryce was buying today go for a GT3071 or GT3076 but given that he already has a GT3040 sitting there it seems worthwhile to bolt it on and see how it feels. There is a probably a loss in response due to the larger comp wheel size but geez if I was carrying around 300kg less in my car it would be hard to notice.

im more than happy to not spend any more money on bolt-ons hahaha, im sure it will feel fine.. ive been in a mates R33 with similar mods and it felt great.. if there's a dramatic problem after i give it a run then i'd consider buying a replacement, but just to get it happening, the 3040 will get a run

A 240 with that kind of power... Someone has a wangan fettish

+1 vote for throw it all together and see what youve got Dont want to go buying new turbos and parts etc etc if your not even sure how your current setup suits your wants/needs. If its not what you wanted, you will atleast have an idea what characteristics you want to change and the relevant data on where to start.

hahaha, yeah wangan is quite cool, but how can you deny the beauty of the 240!

I'm still keen to get some form of internal work done, even if it's just basic replacement and reconditioning.. but we'll see

I reckon just a good tight std RB25DET , maybe a Neo if available , and a 2835 Pro S with the 0.68 turbine housing should work well . A bit more exy but its a bit hit and miss with those 3071Rs and the full sized GT30 turbine . For whatever reasons that cropped turbine and the HKS turbine housing seem to work a bit better over a wider range and the ported comp housing takes care of any surge .

Cheaper and easier would be an RB spec GTRS turbo .

I'd be ditching the 4.6 diff in a car that light and opt for a 3.9 or even a 3.7 ratio final drive . These are still around in the type of long nose R200 that fits under the bum of those early Zeds .

A good RB25 should make more torque down low than a carburetted L24 or L26 so all good .

Yeah , tight Neo 25 with a GTRS would easily be quick enough on the street and very easy to live with as a daily .

With Stuarts steering and suspension bits you could make a very impressive classic that could embarrass many a current lump and hold its own steering/handling/braking wise .

A bonzai engine is expensive where a more conservative and budget conscious one leaves money to make an old car THE complete package . Nicer to drive and easier to sell for good money if you get tired of it .

A .

good points but sounds expensive considering where im at.. i initially wanted to get a Neo but there were stupidly expensive when i was first looking around..

cheers for all your input guys! heres a couple of more pics

[Brycey]

here are a couple of pics i found

[Brycey]

...and one of the areas that requires some attention...

[discopotato03]

Yes Stuart Wilkins is the one to speak to about 240Z/260Z cars . I'd try and do that soon if you are really keen and he may even ask you to trailer the rolling shell out to him at Mulgrave for an inspection .

For fab work with the shell free of components is a real bonus .

People used to say that L Series engines were unburstable but that's obviously not the case . Probably the torquiest NA ones were those with the 83mm LD 28 cranks fitted which got them up close to 3L . If anything the SOHC 12 port (6) heads were the breathing limitations and its not to hard to see the RB engine family as an evolution of the old L engine .

I go so far as to say that the R32 GTST was a modern equivalent of the 70ish 240Z in 1989 . This is where you have to decide if its practical to modernise an old Zed or restore one to its former glory . Same deal with an R32 GTST though I know which is the safer bet driven really hard .

The condition is known as Petrolysis Cranius and the only known cure is bankruptcy .

A .

[jordy R32]

hey mate. i"m putting a rb25det in my 280zx datsun and need some help. how did you combat the clearance problems with the oil sump when you were mounting the motor? cheers,