Specs For Rb20 With Rb26 Crank / Rods

[Spoolup]

Looking for details ( from someone who knows ) on what pistons to use when building an RB20 with RB26 crank and rods. I believe the 4age piston is used ( but which one, turbo, NA ? ).

Tomei make pistons for this setup but at around 2k a set its a little pricey

Any help appreciated ?

[zebra]

I believe its 4ag-ze (the supercharged one)

otherwize you end up with bs amount of compression.

hope this helps

[Spoolup]

yes it does - but still want to hear from someone who has done it.

As the combustion chamber size on the 4 age and RB20 may well vary considerably and the NA 4age might be the go.

Im sure someone will answer the question eventually

[The Dan]

You'll be hard pressed to find someone who has done it to post up here. It's pretty much a waste of time for the amount spent and the very minimal gains achieved.

The pistons you need are 4A-GZE from the suprcharged engine as stated above. These are already a forged piston. 4A-GE pistons are cast and the compression is way too high when you use these.

Also 4A-GZE pistons are not $2k new from Tomei.

[Spoolup]

Thanks

I was referring that Tomei make off the shelf pistons for the RB20 with RB26 crank and rods - and they are 2k.

I would not be using 4age OEM pistons, as Wiseco make both NA ( 4age ) and Turbo/Supercharged ( 4a-gze ) forged pistons.

I am totally aware it is a waste of money and effect but I have a customer dead set on the idea - and the customer is always right :-)

You'll be hard pressed to find someone who has done it to post up here. It's pretty much a waste of time for the amount spent and the very minimal gains achieved.

The pistons you need are 4A-GZE from the suprcharged engine as stated above. These are already a forged piston. 4A-GE pistons are cast and the compression is way too high when you use these.

Also 4A-GZE pistons are not $2k new from Tomei.

[zebra]

Would certainly make 1 tough rb20 though

[Sydneykid]

Thanks

I was referring that Tomei make off the shelf pistons for the RB20 with RB26 crank and rods - and they are 2k.

I would not be using 4age OEM pistons, as Wiseco make both NA ( 4age ) and Turbo/Supercharged ( 4a-gze ) forged pistons.

I am totally aware it is a waste of money and effect but I have a customer dead set on the idea - and the customer is always right :-)

The only reason 4AGZE OE pistons are used is because they are cheap, new and used. They are 81 mm bore and the early ones have 18 mm gudgeons, the later ones are 20 mm, that's gives what is commonly known as an RB23 (2,280 cc's). The RB20 block will take more than 81 mm and the RB26 rods have 20 mm gudgeons, the usual route when using early pistons is to sleave the little ends down to 18mm. So if you are going to use an aftermarket forged piston, then you would be much better of buying something with an 82 mm bore and a 20 mm gudgeon. That will give you an an extra 56 cc's (2,336cc's) for no extra cost.

ACL make a Race Series 4AGZE pistons that is 1 mm oversize (82 mm) with the later (20mm) gudgeon the part is 4MKRY9634. Last time I checked they were very reasonably priced, we use them in the 7F bottom end (1,807 cc's) and 20 valve top end race engines.

Cheers

Gary

[Spoolup]

I knew you would be lurking around here somewhere with the answer.

[chris_r31]

sydneykid: power gains, or even reliabilty?

is this a good option to take, an is it worth it?

obviously other suporting mods will be on, but this is yet another idea for my rb20 build..

i dont no why but i just love the rb20's, hence my big build....

[Sydneykid]

sydneykid: power gains, or even reliabilty?

is this a good option to take, an is it worth it?

obviously other suporting mods will be on, but this is yet another idea for my rb20 build..

i dont no why but i just love the rb20's, hence my big build....

Simply put it is not worth doing, I have all the bits necessary to build an RB24, have had for years. But I have built 3 RB30's in that time, why? Because they are far better value for money. The only reason I have kept the RB24 stuff for the R32GTST is that Improved Production has no minimum weight limit if you use the original block and head. One day I might use it, not for power or cost, but so I have no weight limit.

Cheers

Gary

[limpus]

I am about to head down a similar path with a spare rb20 i was given...only in my case i will be using a rb25 crank and rods with the 4agze pistons...i know gains are minimal...i'm only doing it as an experiment/exercise and also because i have a free engine...

[chris_r31]

Simply put it is not worth doing, I have all the bits necessary to build an RB24, have had for years. But I have built 3 RB30's in that time, why? Because they are far better value for money. The only reason I have kept the RB24 stuff for the R32GTST is that Improved Production has no minimum weight limit if you use the original block and head. One day I might use it, not for power or cost, but so I have no weight limit.

Cheers

Gary

i have a spare rb30et which made 345rwkw's in my old vl, 3speed auto with full manualised body..

i dont know y but i dont have the drive to put it in the r32, my 160kw rb20 was fun as hell, but it was lacking the extra power for just that extra bit of fun..

so thats y i want to build it up and strap a big snail to it. but yet again i get told its a waste..

i cant argue with experiance, but im disapointed. there such a fun engine..

[Roy]

There is no denying that RB30 will give you results. But personally i love the character of a 2L with a large "tahbin" Just driving around off boost with the thing spooling up and never really boosting over 3-4psi, it sounds like an angry giant ready to awaken When you do get a hit you smile all day because of the way power comes on

[Spoolup]

So there is no drama boring the RB20 out for 78mm to 81 or 82mm ?

Cheers

The only reason 4AGZE OE pistons are used is because they are cheap, new and used. They are 81 mm bore and the early ones have 18 mm gudgeons, the later ones are 20 mm, that's gives what is commonly known as an RB23 (2,280 cc's). The RB20 block will take more than 81 mm and the RB26 rods have 20 mm gudgeons, the usual route when using early pistons is to sleave the little ends down to 18mm. So if you are going to use an aftermarket forged piston, then you would be much better of buying something with an 82 mm bore and a 20 mm gudgeon. That will give you an an extra 56 cc's (2,336cc's) for no extra cost.

ACL make a Race Series 4AGZE pistons that is 1 mm oversize (82 mm) with the later (20mm) gudgeon the part is 4MKRY9634. Last time I checked they were very reasonably priced, we use them in the 7F bottom end (1,807 cc's) and 20 valve top end race engines.

Cheers

Gary

[raZ1911]

Has anyone here really done the RB24 to feel what its like?

[limpus]

There are a few guys here that have rb24s...but the general public is still unconvinced about it...it will never be as torquey as a standard rb25 but its a fair improvement over a standard 20...it is however going to be much tougher and more reliable than a standard rb25...a rebuilt and forged 25 again will probably sh!t all over it...to each his own in the end...

[infamous_t]

There was a big thread about a year ago by someone doing the rb24 combo, ill see if I can find it...

[infamous_t]

http://www.skylinesaustralia.com/forums/Pr...tml&hl=rb24

Hope that is of some use to you

I think the rb24 could potentially be a great engine, especially for those trying to fit into a specific class for racing etc.

There are ppl out there with built rb20s that are more than happy with the results, so I can on see the rb24 being a great thing... but personally I'd be putting a '30 bottom end to my 26 for the money.

[chris_r31]

roy im with you, im a rb20 lover, but i have blown so much cash on cars its not funny, this will be my last built , cause priority is becoming a factor in my life now lol..

i just dont want to waste 10 to 15k on an engine build that hasnt got much more over a standard rebuilt rb20 with 17psi threw it with some nice lag...

but still have to read up on this rb24 combo...