Best Option, RB24??, 25 0r 26

[drifto]

I would like some help with the options I'm looking at.

My 32 gts is street driven, but needs to be strong and reliable for light competion use in hill climbs, super sprints and tarmac rallies events.

With it's original RB20, a few bolt on support systems and a 15psi via an old HKS turbo it was making a healthy 200rwkw. However it has now lost a significant amount of compression and needs replacing or a rebuild.

Option A: rebuild another RB20 with GTR crank, rods & forged toyota pistons giving me @ 2.4 litres

Option B: fit an RB25

Option C: fit an RB26

I want at least the same level of power as before with increased torque in the lower revs.

I'm not sure how much money needs to be spent on top of the first two options in order to achieve the same performance and reliability level of an RB26.

But Option B & C will not be rebuilt after purchasing due to the initial outlay.

Anyone done anything like this and whats involved that i may not know about??

[blind_elk]

You need to be mindful of the allowable modifications in each event.

I would expect the best bang for your buck will be the RB25DET upgrade. But you'll need the ECU as well. More low-down torque from the increased capacity, just as much up top.

The RB24, as well as the cost of the build, will require a re-program of the R32 ECU, or an aftermarket job.

The RB26DETT is just too expensive for the purpose (more serious motorsport might justify it)

[SLY33]

hi drifto. The RB24 sounds cool, but i agree with the best bang for your buck being an rb25. This motor will do ~200rwkw in its sleep with the stock turbo and an aft. ECU, plus have good torque. You may even be able to use your old HKS turbo for more power. What turbo do you have?

[46n2]

I've done a bit of investigating for an RB24 (or even 22) conversion, and you're looking at big $. Sydneykid & Rob helped me out with a lot of info. I would point you to the thread, but it's disappeared in the lost month of November maybe tis could be the start of the new thread. I'm looking for the same as you pretty much. A stronger, more reliable engine. I've been looking at a lot of the Tomei internals...but there is still much research to be done. email me [email protected] we could share info as we come across it. where do you live?

[Clint32]

option D, look around and buy a stuffed rb25 with cracked pistons, without turbo you can score for between 800-1000, then get it built properly for about 4.5k, which it will cost to do the rb24 anyway.

[46n2]

A properly done RB24 conversion is going to cost a lot more than 4.5K. 4.5K will buy you the pistons and rods...then there's the crank (RB26 - $$$), valvetrain, boring of the block, boring the head to match, bearings, machining of the block to fit the oversized crank, ECU...

I'm putting together some costs soon to ease my own curiousity (it won't be for a few weeks though - moving south ). I'd be more than happy to share my results with anyone who's interested

but agreed...the rb25 conversion is definitely the cheaper option

[Roy]

Id say it really depends on how much money you have and how far you are willing to go.

Things i would be considering when looking at which avenue to take is:

- will you be happy running the std RB20 5 spd behind whatever you build

- are you going to upgrade the turbo

I wouldnt consider the Rb25 myslef, unless of course you get a good price on a perfectly running example.

The price of getting an unknown quantity in the shape of an RB25 which is still going to cost you upwards of $1500, if rather be throwing that money at an RB24. (Unless you think you will approach a power level where the smaller RB20 valves will be hurting power)

Depending on what you are doing with your current turbo, id say rebuild the RB20 -> RB22 with 82mm pistons, and some cams, (GTR valvetrain perhaps) OR build up a RB30DET.

But if you can scratch together the GTR crank and rods for a reasonable price, then i would be taking that path.

[46n2]

Hey Roy...Where abouts in Sydney do you live? I'm moving to VIC in a few weeks and I'll be passing thru Sydney on the way down. I'd love to swap ideas.

[mist]

that old RB22/23/24 thread was lost? What a shame =/

[46n2]

yeah I know there was sooo much info in there too :

[Sydneykid]

Hi guys, this is some of the stuff I posted in that thread........

An RB20 is 78 mm bore and RB25, RB26 and RB30 are all 86 mm bore. You can't bore a RB20 block 8 mm oversize. So you can't use RB25, RB26 or RB30 pistons in an RB20. About 82 mm is about as big as you can go (4AGZE pistons are a common choice).

An RB20 has a 69.7 mm stroke and RB25 is 71 mm, RB26 is 73.7 mm and RB30 is 85 mm. You can use an RB25 and RB26 crank and rods in an RB20 block. RB30 won't fit. RB25 fits in no mods RB26 needs a little work on the block to clear the crank counterweights and rod bolts.

Using an RB26 crank and rods and 4AGZE pistons gives around 2340 cc's.

If you add it all up I bet an RB25DET will be cheaper and at 2,476 cc's bigger as well.

If you want to see how this sort of rebuild goes, check out JOnJOn's posts as he is doing exactly that.

[Clint32]

sydneykid would you know the approx displacement of a rb25 with gtr crank and 40tho oversize gtr pistons, cheers Clint

[Sydneykid]

Hi Clint, 2630 cc's, same as a GTR with 87 mm pistons.

[JezR31]

Heres all the Rb24 pages i found. I hope this can help abit.

RB24

RB24?

stroked RB20

New engine questions, - sydneykid?

[drifto]

Good comments Guys, Cheers

I'm waiting for a qoute from my engine builder who just happened to have a GTR crank & set of rods. He also suggested the toyota forged pistons which are reasonably priced compared to custom forgys or aftermarket jappo ones.

I will post this option as it comes together.

Meanwhile my engine wont even start, mechanic thinks now that the comp ratio is so low in some of the cylinders that it can't kick.

It had been running pretty well before so some damage may have been done when the original leaky injector prob caused a severe flooding of the engine.

He has got it to start but only by taking all the full pressure out of the rail to about 12psi, as soon as the fuel press is normal about 35psi it floods and stalls??????

So now i'v gotta put a new engine in. Apparently!!!

$700 for 2nd hand rb20 minus turbs, $600 for install labour

Should i just go an rb25 now instead?

I already have APEX piggy back AFC & ITC

GTR fuel pump & adjustable fuel reg

A steel wheel HKS turbo of uknown specs (200rwkw 15psi RB20)

[Bl4cK32]

Option E : RB30det

Increased torque over all other engines mentioned, and power delivery is right at the start of the rev range.

And for all of u who say "yer but it doesn't rev" - Add a 264 cam and it powers to 7500 rpm.

Can't beat that now can ya?

[drifto]

Checked out those other posts, thanks Skyline Boy!

Seems my RB24 will be limited straight away by the stock head unless i'm gonna port, valve & cam it.

I'v heard the same regarding the 25 head tho ?

Would a 25 conversion require changes to the gearbox, clutch or other things apart from the hassle of having the new dispacement certified and engineered.

If i throw another rb20 in now then build my original one I can put it back in with original engine numbers before rego is up and no one the wiser about it 2.4 capacity.

The questions are, what is the standard head capable of flowing as i'm not after top end peak power but a torquey power curve that will stay stong till about 7500 rpm

Would my existing HKS turbo be too small for the 2.4 capacity? either way it has to be better than a stock rb25 ceramic wheel.

If we can keep this thread going for a while i'll post results and experiencres as it happens.

Should be good info for a lot of skyline owners looking at rebuild options.

[drifto]

I don't like the idea of a rb30 for a number of reason,

they came in commodores

they are single cam, unless you spend lots of money purchasing and fitting a 25 or 26 head

i'll definatley need a new turbo for 3 litre capacity

rego, insurance, resale

It also changes the cars character too much!

But thanks anyway for your option

[Bl4cK32]

the rb 30 is a nissan engine.

the dohc head costs 750 comes with inlet manifold, fuel rail etc.

the r32 rb25de head is a straight bolt on to the rb30e bottom end - no modification.

your turbo is fine (im using the rb20 one which is high flowed till i can afford the biggun)

rego, insurance, dont tell em

resale - prolly get more buyers

changing cars character - what, u like a lotta lag? stalling it to 3500 to take off at a decent speed?

[DCIEVE]

how do the rb30 internals handle that much revs?