Rb20det To Rb22det?

[RB20DET_Silvia]

Hey guys,

I seen some where if u drop RB26 rods and crank into your car it should turn it in a 2.2litre RB20.....is this true, i think it is but im wondering will these just drop in with no other mods......and is it really worth the work and money for an extra .2 of a litre.

How much would it cost and is it worth it?

- Luke

[Col-GTSX]

Dont see how...

I mean i did a JUN 2.2 kit on my second GTS-X and the crank was totally different to a stock rb26 one...

I just dont see it turning in that little bore. I mean the counter waits...

I dont think the rb26 bearing will fit the rb20 block in fact im sure they wont. Also you can't use the rb20 bearings as their smaller on the big ends....

Anyways by the time you get these parts you will have spent enough money to pay for a full JUN kit brand new...

I paid AUD $3400 for the kit when i was in japan on holidays.

The kit included pistons, crank, rods, bearings & rings.

I also purchased cams and other bits and pieces to suit at an extra cost.

Edited December 22, 2005 by Col-GTSX

[carl h]

yes it can be done, tomei supplies pistons to suit a 2.2l rb20 that is achieved by boring the motor to 82mm.

rb26 bits DO fit but the block has to be clearanced for it to fit.

using rb26 bits (crank, rods, bearings) and special pistons (tomei in this case) gives you a 2.4l rb20 with a capable 9k redline due to the rb26's better crank and rods...........

but like i said above tomei does sell 82mm pistons to bring it out to a 2.2 using stock rods.

Edited December 22, 2005 by carl h

[RB20DET_Silvia]

So what would be involved when buy these pistons....would u have ur engine bored or honed or something to fit these new pistons in?

And what would the advantage be.....much more low down torque....etc...what would be so good about it?

- Luke

[Sydneykid]

This is a very common topic, do a search on RB23 and RB24.

Here is one of my posts on this subject....

Hi guys, I will try and answer the questions, but before I do I should point out that you can swap most of your good bits onto/into an RB25DET and end up with a better result than building an RB23/RB24. And it will cost a damn site less as well.

On to the questions;

The standard RB20 bore is 78 mm, the most common RB23 (2,280 cc's) piston upgrade is 4AGZE which are 81 mm (from memory). This means you will need to relieve the combustion chambers radius at the bore by 1.5. Then taper it into the normal combustion chamber shape. Pretty simple really, any machine shop could do it.

You will need to relieve the combustion chamber volume to achieve your target compression ratio. From memory about 3 cc (slightly more than a good polish) gives 8.8 to 1 for an RB23. The combustion chamber volumes will have to be equalised of course.

Porting is pretty much essential if you want to use the higher rpm effectively without huge amounts of boost. There is a lot of work on both the inlet and exhaust ports needed. If you do a really good job, you should end up around 85% of what a standard RB25 cylinder head flows.

Depending on the experience of the machinist and the workshop hourly rate you are looking at around $1K to do the above.

There are larger valves available for RB20's , I have seen 2mm larger inlet valves and 1.5 mm larger exhaut valves. I have a recollection that they were for a VG30 or CA18 but they fit the RB20. Since VG30's are popular in the US there are quite a few valve, valve spring alteratives. A quick check of the sizes should confirm the suitability.

From memory the VG30 valves where around $US20 each, so that's $640 for the set plus freight.

RB26 cranks vary considerably in price, I have seen R32GTR cranks around $400, rods around $200. Up to double that for R33GTR cranks and rods. The best suggestion I can make is to shop around the For Sale forum and check out the historic prices.

As for cams, 256 to 264's would be fine for using with the hydraulic followers (260 Poncams for example) . But to really use 272's or higher you would need to do a solid follower conversion. No, RB26 bits won't fit, well not without some serious engineering and machining. But CA18/VG30 may well fit, worth checking anyway.

By the time you have the necessary RB23/RB24 parts purchased, get it all machined and assembled you are looking at a bit over $5K. Then you have to add the accessories, manifolds, turbos etc.

Hope that was of some help

cheers

[Waldo]

So sydney kid wat your saying is that most of your rb20 good parts will bolt into a RB25?? like if i went out and bought a rb25 would my rb20 tomei cams fit straight in...and how would i get my gtr injectors to work or even fit.....could i still use my ap engineering power fc with this motor...and my rb20 splitfire coilpacks??? if all this stuff fits im gettin one next week

[R31Nismoid]

This is a very common topic, do a search on RB23 and RB24.

Agreed

[RB20DET SILVIA]

ne 1 know where we can get all the bits we need to make it a 2.2? or just forge the 2.0..?

[Waldo]

sry r31nismoid i cant find anything on swapping rb20 parts over to a rb25 anywhere on this site....is an rb25 just a straight swap over with wiring loom if you get rid of the VVT??

[Nathan_G1]

depends where your from. Terry from kansai automotive here in adelaide is getting his shipment very soon, stocking some RB26 cranks and conrods.....i think he's using an Rb20 to test the conversion himself, bores it out to roughly a 2.3 ltr withou pistons.....coz u dont actually need to change pistons, but if the cash is there...DO IT! Give Kansai an email and he should hopefuly help you somehow. www.kansaiautomotive.com.au or just .com cant remember, i practically live there lol so i never go no the site