Rb20/25

[7yphon]

I have a RB20DET which it states on my sig, anyway down to the point. I have just been given access to a RB25det bottem end now there is nothing wrong with it "YET" because my mate is going to be doing a RB30DET conversion so he now no longer needs it, I was thinking about slapping this onto the bottom of the 20 is there any issues I should know about, Is it a Direct Bolt on? and what should I change while its not on a engine?

[race_snooze]

I would assume that it will bring up the compression ration, also doesnt the rb20 head have smaller ports then the 25?? and less flow?? I am not to sure on this, but someone on here will know for sure

[R31Nismoid]

in simple terms

waste of time

cheers

[7yphon]

I dont care about the time and its free why would you argue about something thats free? Also im going to be doing the rebuild myself, Also if the ports are smaller why would this matter? I wanted info on the conversion, Why do ppl always have to shoot peoples ideas down

[R31Nismoid]

because if you used the search button you'd find out why.

people get tired of repeating themselves over and over

[7yphon]

I have tried the Search button, What do I need to type and I wont ask these stuped questions?

[7yphon]

Well I have tried to search for the last few hours now and still no more information alltho I did read something about this being another way for a RB24? is this correct. and please please help I know you might have said stuff to other ppl before but if you have its been lost or I dont know what to search for.

[Guilt-Toy]

I think to do the rb24 you need RB26 parts.

[7yphon]

ok this is what im looking at doing, Please advise.

ok if I can track down a RB25 head it will be a fully rebuilt RB25

I want to use RB26 parts but I heard the crank will not fit. is this the case?

I was thinking like the 24 bore it out to 83. and using the 4agze pistons.

I was also thinking about using RB26 conrods

I will have to use the RB20 intake and anything else that needs to be bolted on.

anyway Feed back please, And try and keep the sarcazem away as I need peoples help not crap.

[TTT]

well it's no longer free is it?

all those parts will cost you money.

and that is more money than buying a perfectly good RB25det.

I'm also no too sure what it is you are trying to build here.

an RB24 is made using the rb20 bottom end. not rb25.

I'm not giving you crap.. just past pointers given to me when I started a thread "Hybrid RB's" where I asked what other heads and bottom end combo's can be done.

[Bl4cK32]

easiest solution is buy a r32 rb25de head, buy a headgasket to get 8:5 - 9:1 compression. Bolt it - to the rb25det bottom end- and use all the rb20 sensors, and loom, then u are away.

Dont bother with the rb24 (rb20 with rb26 crank + 4agze pistons). If you want to spend more just fit the 26 crank + rods + pistons to the 25 setup for a 2.6lt...

Edited April 11, 2006 by Bl4cK32

[7yphon]

well it's no longer free is it?

all those parts will cost you money.

and that is more money than buying a perfectly good RB25det.

I'm also no too sure what it is you are trying to build here.

an RB24 is made using the rb20 bottom end. not rb25.

I'm not giving you crap.. just past pointers given to me when I started a thread "Hybrid RB's" where I asked what other heads and bottom end combo's can be done.

ok its still free but with the parts im buying I am hoping to make a better/stronger engine then stock, I am building this engine towards race/drift so I want it to last but I also want some touque because thats what wins races.

Also I did think about the R32 25de head but I wasnt sure if it would surport the build up but I guess I can keep the loom then.

Cool been heaps of help guys ill look around a bit for some more ideas, Also do I need a R33 ECU or could I chip the 32 one to support the mods?

[Guilt-Toy]

mate your wasting your time and our time.

[Bl4cK32]

Thats a bit harsh.

If he has the time, and money whats the harm in asking q's about it? thats what the forum is for.

You use the ecu to suit the sensors u are using. I suggested the r32 rb25de head as it has the same size valves as the r33 rb25det head, but minus the vvt, so you can keep the rb20 loom and sensors.

If you want to chip the r32 stock ecu, just stay away from 550cc injectors as they have idle issues on remaps. Or go for a pfc.

Really you are only up for the head (~$750) then tuning. If you want to push it further then u are up for the usual items everyone needs at higher power levels. A rb25 in a r32 is a great swap.

[Guilt-Toy]

Its not going to be easy to do this conversion.

Its just not feasable to put the rb20 head onto the rb25 bottom end. Its a waste of time and money you could have a whole rb25DET engine for the same price.

First you will need to find a RB25 head and you will be looking at around $800 for the head (depends how lucky you are)

once you get the head and bolt it all together you still need to get the computer / injectors / AFM / wireing sorted out.

Then you will need a stronger gearbox because the 20 box will last you a few months depending how you drive.

So if you are looking at spending some big $$ on your car you could do it properly and get a RB25DET with box and computer etc etc rip out your rb20 & box and sell it to recoop some costs.

if you do it your way there will be lots of mucking around and the end result still will not be as good as nice rb25det.

ive been through modding a car with what youve got and all it ever did was cause headache after headache. do it properly the first time and you will never look back.

maybe you are better off getting 2530 (turbo) some injectors and a power fc to get more power the standard 25 will get for less $$$$$

hope this helps

Edited April 11, 2006 by Guilt-Toy

[Sydneykid]

This thread is TOTALLY confusing.............

Let get rid of the RB20 cylinder head on RB25/26/30 idea first.

The bores are different sizes RB20 = 78 mm, RB25/36/30 = 86 mm

The water jackets are in different places.

The oil feeds are in different places.

That means considerable alloy welding and redrilling of the RB20 cylinder head.

It Would be cheaper to buy a complete RB25DET than pay someone to do the work. I know becuase we did it about 15 years ago (RB20 head on RB30 block) it was a bitch of a job.

Does that kill the RB20 cylinder head idea?

cheers

[Bl4cK32]

sorry i should have made myself more clear to start with. - first post edited to reflect

I was referring him to use the rb25de head on the free rb25det bottom end that he was getting.

In no way would i suggest to someone to put the 20 head on the 25/26/30 bottom end.

Edited April 11, 2006 by Bl4cK32

[Guilt-Toy]

This thread is TOTALLY confusing.............

Let get rid of the RB20 cylinder head on RB25/26/30 idea first.

The bores are different sizes RB20 = 78 mm, RB25/36/30 = 86 mm

The water jackets are in different places.

The oil feeds are in different places.

That means considerable alloy welding and redrilling of the RB20 cylinder head.

It Would be cheaper to buy a complete RB25DET than pay someone to do the work. I know becuase we did it about 15 years ago (RB20 head on RB30 block) it was a bitch of a job.

Does that kill the RB20 cylinder head idea?

cheers

Cheer !! *clap*

Like i said its a complete waste of time!!

If you want power your options are.

1: get a full RB25DET conversion kit with gearbox and go the whole hog.

2: get a rb25de or t head and bolt it to what you have and be prepared to spend some $$ chasing your tail

3: get a HKS 2530 some injectors a power FC and a nice front mount for more power you would get out of step 1 and 2 and will be much more practicle and easier with no stuffing around.

If I were you I would go option 3.

Well.. maybe i would go with option 4

4: Get a 3 litre bottom and and a 25 head and start working on a real engine =)

[Bl4cK32]

At the end of the day its up to him.

I suggested just buying a r32 rb25de head and slapping it on the free rb25det bottom end he is getting, bolting it all in and hes only spent for the head.

He wont need to worry about getting a complete rb25det as its what he will have. Torque kills gearboxes, so he wont have to worry about it, unless he plans to go over say 250rwkw anyway.

If he does decide to go past that he will require all the mods others require to get past that power level anyway, like pfc, inj, afm etc....

Cheapest option for him is just to buy the rb25de head and bolt it all in and have a 2.5Lt r32. Its the same as buying a complete rb25det and dropping it in without farking around with looms etc, as there is no vvt to worry about.

We are all in agreement that anything other than a rb20 head on the rb20 block is a waste....

As for the 3lt it will require more mods than dropping in the 25 i suggested...

[Guilt-Toy]

At the end of the day its up to him.

I suggested just buying a r32 rb25de head and slapping it on the free rb25det bottom end he is getting, bolting it all in and hes only spent for the head.

He wont need to worry about getting a complete rb25det as its what he will have. Torque kills gearboxes, so he wont have to worry about it, unless he plans to go over say 250rwkw anyway.

If he does decide to go past that he will require all the mods others require to get past that power level anyway, like pfc, inj, afm etc....

Cheapest option for him is just to buy the rb25de head and bolt it all in and have a 2.5Lt r32. Its the same as buying a complete rb25det and dropping it in without farking around with looms etc, as there is no vvt to worry about.

We are all in agreement that anything other than a rb20 head on the rb20 block is a waste....

As for the 3lt it will require more mods than dropping in the 25 i suggested...

So when he drops in the 2.5 litre how much bang for buck is he getting ??? I would estimate it would cost around $1400 by the time you buy gaskets and oil and get it running.

You will then be running a rb20 turbo on a rb25.

Why is not better to just upgrade the turbo and get a SAFC2 or something and run a bar of boost for around the same price ?

I know what would get more power.