rb25 to rb30

[Kor'axis]

what is involved in putting a rb30 onto rb25? i did the search and didn't find anything specific on it. What parts would you need to swap over and how much would the costs be?

would you get the rb30 from a VL or a r31 (differences/similarities)

[Cubes]

There is a thread sticky at the top of forced induction performance.

I'll give a quick run down though.

You need a Series 2!!! VL Commodore RB30E block.

If doing it properly I would seriously look at a set of aftermarket pistons that raise the compression ratio to around 10:1 if you are making it an NA motor.

Even with my 8.2:1 comp it is a very very punchy motor, it probably also has a little to do with the gear ratio's.

But that being said.. If you are going to the expense of a motor build you would probably be better off building it to suit turbo or even better buying a turbo model & rip the turbo off if insurance is too high then drive it around as NA for a while until you can justify spending the $$.

OR.. go a cheaper R32 and drop a RB25 or RB30DET in it.. Insurance is obviously cheaper than the R32's. It all comes down to if you can put up with the smaller older car.

Personally I like the feel and throwability of the R32's on the road but I prefer the look of the R33's.

[Kor'axis]

i read over some of the other thread and as i'm still a noobie i'm still a bit uncertain on some details. if anyone can help?

1. The other thread refers to a GTS-T because mine is a NA s1 r33 rb25de will it still work?

2. New pistons required? - I imagine so as different volume?

3. JNR24 said he got it acid dipped, cleaned, and machined a bit more... this means you'd have to get new pistons.... if you do this?

4. What other engine parts would you need? Rods?

5. Bearings?

thanks

[Cubes]

Some of the questions there show that you lack some vital mechanical knowledge.

If you want to do this conversion without paying some one else to do the research and labour then I suggest you start reading & googling. Head down to the local library borrow books and get a decent knowledge of the mechanical side of things. Then you will be able to asking more relevant questions like.

How much do I have to lower the engine by to clear the bonnet.

The other thread refers to a GTS-T because mine is a NA s1 r33 rb25de will it still work?

Why wouldn't it? Turbo is simply a mechanical device hanging off the side of the motor. Removing it will leave the car simply running in N/A form. So Yes..

[Kor'axis]

No, i always intended to get someone to do it for me as i really don't trust myself not to stuff it up, i just wanted to know which parts i would have to source and from what i've read on the forums there are some differences between the turbo and non turbo engine and i wasn't sure whether that would impact the requirements for the conversion

[paulr33]

hey koraxis ill give you a bit of crash course, i mean i dont know it all either and i could be wrong, here's what i posted in another thread a few minutes ago re: converting R33 GTS to rb30

> i dunno i reckon an rb30 bottom end conversion would be tops as for it, as the gts n/a would be cheap as to get and you can get > the rb30 block for like $300. then do a 25/30 conversion on it, 3.0 block 2.5 twin cam head with turbo manifold would be a > monster the rb30 howto even says to use the n/a 2.5 head and change the brakes

> i wouldnt keep stock r33 gtst brakes on an rb30 conversion so it doesnt apply you could just get slotted and drilled rotors from > dba (dba4000) and youll have to upgrade clutch and other shit if you did it in a gtst anyway so its no diff really, just a > cheaper base car. the stock gtst clutch/brakes/cooler wont take the torque of the rb30, well it well just very badly and not > wise. rb30 gt340 highmount it would be an absolute killer i think the stock rb30 with the r33 turbo winds up boost from like > 1300rpm or something stupid, whereas stock r33 gtst hits 7psi at about 2500rpm (well mine does) or just a tiny bit over 2600rpm > maybe

>

> something to consider

>

> rb30 should set you back around 4-5k ? check out the rb30 howto

if you read the rb30 howto pdf it tells you what you need. I think the guide assumes you are coming from an r33 gtst but thats ok if its an n/a as you would change most of the stock running gear anyway if you were serious about, the stock gtst clutch will be angry with an rb30 conversion on it as the stock gtst clutch will slip around 190rwkw and the rb30 conversion should pump out more than that

1. The other thread refers to a GTS-T because mine is a NA s1 r33 rb25de will it still work?

yes it should, even the pdf states you can just use a rb25de head (which you have) and an rb30 block

2. New pistons required? - I imagine so as different volume?

yes new pistons would be require, get forgies if you doing the build

3. JNR24 said he got it acid dipped, cleaned, and machined a bit more... this means you'd have to get new pistons.... if you do

this?

yes this is correct as you want the block in tip top condition seeing as youve gone to effort to dismantle it may as well clean it up, check it etc

4. What other engine parts would you need? Rods?

rb25/rb26 rods are ok, im not 100% sure on rb25de rods but rb25det rods are fine and i dont think theyre different

youll need an ecu to run it, heres a summary from the pdf

heads: rb25de head is fine

head gasket: new rb30 gasket is recommended

plenum: rb25de should be fine as its the same head/plenum

block: rb30 series 2, the series 2 block has the turbo oil/water lines already done and ready to go

if you get series 1 you have to drill them out (not a massive problem but an issue)

sump: you need to grind part of to make the block bolts fit

pistons: it says to get rb30e (not rb30et) pistions and use them, id go forgies myself for "strength" reasons

rods: "prepped" stock rods will handle 350rwkw

crank: needs to be sleved if the rb30 is very old and has oodles of kms on it

oil pumop: rb30 oil pump is fine or rb26 if you want a rev monster youll need a bigger flow oil pump

water pump: cheapest is rb20e water pump, $90 new. rb25de thermostat

flyhweel: rb25 flywheel is ok so it says. youll need a suitable clutch, twin plate at a guess?

ecu: apexi power fc is reocmmended

afm: z32 (from 300zx) is recommended but you can use stock rb25 one, it will give bullshit figuires to ecu above around 250rwkw

injectors: rb25de injectors are fine upto 240rwkw

turbo: gt30 (270rwkw ish?) or gt35 (300+ rwkw)

gearbox: rb25det box will hold around 450rwkw, unsure of rb25de gearbox

joels comment re: loweing bonnet is because the rb30 block is higher and with the head etc placed on top the clearance is less and it will just touch your stock bonnet so you need to lower the engine mounts im pretty sure thats how joel'/the pdf do it

all of this info can be found on this site and read up, check out archives from sydneykid/joel/meggala and the massive 50odd page rb30 howto page on this forum

[paulr33]

rb30 from vl and r31 is pretty much the same, most of the parts you can get to suit rb30 also as stated above from holden and they're probably a tiny bit cheaper like oil pump, water pump brand new

[paully_tee]

i asked the guys at hyperdrive abt this. they seem to rekon it wasnt worth it. sayin the rb30 would run like shit and its basikalli a step backwards

[Cubes]

Paully,

If I were you I wouldn't be going back to hyperdrive.

Exactly what were their reasoning behind their..

they seem to rekon it wasnt worth it. sayin the rb30 would run like shit and its basikalli a step backwards

Obviously they know very little of how well the bottom end of the RB30 has been setup from factory regarding its rod to stroke ratio and strength.

That with the better breathing twin cam head really makes it an economical and powerful motor.

[paulr33]

whos hyperdrive? ive never heard of them, sorry if i posted wrong info

[Cubes]

Sorry, Paully_tee deleted his thread.

[paulr33]

haha sweet, hows the rb30det going anyway

[paully_tee]

lol. sorry. my original post said: i asked the guys at hyperdrive abt puttin a rb30 into a r33. they said it wasnt worth it and was basikalli a step backwards.

i deleted the post cuz i didnt wanna step on any toes or offend hyperdrive.

[Cubes]

I think they are more scared of the unknown, of having to do the research to get it sorted.

[paulr33]

a step backwards? rebuilt bottom end, more torque, get a chance to do forged internals, better powercurve, boost comes on earlier, what more could u want? and best of all the parts are cheap

[Cubes]

The 3ltr definately is awesome.

Being a larger motor it should be running cams around the region of 260inlet and 260exhaust. Obviously running the smaller cams that are designed around the 2.5ltr its going to drop torque over 6000rpm quite rapidly.

[rsx84]

i'm thinking of the N/A rb25 head going onto my r31 rb30e, keeping it N/A, i was talking to a bloke on the r31 forum, who said that if you use the pistons from the rb25de in the rb30 block then that will be good for the 10:1 comp, also if you use a SAFC that will be able to change the fuel "mapping" for the extra fuel required!

[Cubes]

The RB25DE runs some where around a 10:1 comp ratio with the shorter stroke hence less displacement vs the rb30.

Use these pistons in the longer stroke RB30 and you will have a higher comp than what the RB25DE runs. To try and make sense of it consider the RB25DE sucks in 10 parts of air, the rb30 having a longer stroke will suck in say 12parts of air. When it reaches top dead center it will create a higher static compression ratio as it has sucked in more air to start with.

You would have to work it out, but it will most definately be higher than what the RB25DE runs standard.

On premium fuel with the correct ignition mapping it will be a good setup and make good power.

[rsx84]

The RB25DE runs some where around a 10:1 comp ratio with the shorter stroke hence less displacement vs the rb30.

 

Use these pistons in the longer stroke RB30 and you will have a higher comp than what the RB25DE runs. To try and make sense of it consider the RB25DE sucks in 10 parts of air, the rb30 having a longer stroke will suck in say 12parts of air. When it reaches top dead center it will create a higher static compression ratio as it has sucked in more air to start with.

 

You would have to work it out, but it will most definately be higher than what the RB25DE runs standard.

 

On premium fuel with the correct ignition mapping it will be a good setup and make good power.

it gives a 10.5:1 comp, hence the safc to play with the a/f ratio i'd say ?? all i know is thats his set up and it works?? cheers

[Cubes]

It will work.. Just be carefull it doesn't detonate on hot days and always run 98 fuel.