Rb2.8ltr Rod On Rb25det Stock Crank

[naklaju]

The spec here looks like it can be match..anyone try this before??

Type SR20 RB26/25 RB28 VQ35

Con-rod Length L(mm) 136.3 121.5 119.5 144.2

L.Diam.xLength DxB(mm) φ51x22.8 φ51x21.8 φ51x21.8 φ55x20.8

S.Diam.xLength

(Bush Inner Cir.) d x b(mm) φ22x22.8 φ21x21.8 φ21x21.8 φ22x20.8

Material SNCM 439 SNCM 439 SNCM 439 SNCM 439

Con-rod

bolt Bolt size ARP3/8-24 ARP3/8-24 ARP3/8-24 ARP3/8-24

Hight under Neck (mm) 40 40 40 40

Con-rod

bearing Inner Circum. (mm) φ48 φ48 φ48 φ52

Bearing width (mm) 17 * 17 17 16.5

Edited May 11, 2007 by naklaju

[Devils_Advocate21]

bore and stroke is 2.8L what piston are you going to use with them?

[naklaju]

bore 87mm (tomei forged piston)

119.5mm rod length

the rod length of the RB25det is 121.5 mm.

Edited May 11, 2007 by naklaju

[BHDave]

No, it doesn't work.

You haven't changed the stroke so you don't get an increase in capacity by running a shorter rod. What you get is a bigger gap (2mm in this case) on top of the piston combined with bigger rod angles.

That rod is made to run with the tomei long throw crank so that the piston retains some meat in the crown above the gudgeon pin without punching a hole in the head wen it gets to tdc.

[tridentt150v]

You'll only get a bigger gap at tdc if the gudgeon pin to piston crown measurement is the same as std. If the gudgeon pin is lower in the piston you could get no gap or worse still it could hit the valves and head.

Inversely, if you get a wrist pin location higher in the piston then you end up with a huge gap above it at tdc.

Any which way you look at it, its not worth doing [unless you are stroking].

So it depends on the piston dimensions as well. BTW BHDave is correct in that you will get no increase in capacity, you need the crank to have a longer throw to increase the stroke. Or bore it out to a larger piston size.

Edit: Tomei piston I don't know which one you are looking at, but gudgeon pin location should be same as std.

[Gav]

Interesting - I had always assumed the rods for the RB26 and RB28 cranks were the same (for HKS anyway).

I'm using RB26 rods (Pauter) with an HKS RB28 crank so far without problems (touch wood!)

[JETZLR]

Interesting - I had always assumed the rods for the RB26 and RB28 cranks were the same (for HKS anyway).

I'm using RB26 rods (Pauter) with an HKS RB28 crank so far without problems (touch wood!)

Not sure about the HKS kit but with the Tomei kit the rods are differant. RB26 stock are 121.5mm and RB28 are 119.5mm. With the Tomei kit it is the crank and rods that are differant but pistons seem to be the same.

[Gav]

The HKS "stroker"pistons have a different wrist pin height compared to the "standard" pistons.

It sound like this is how HKS accomodate for the difference in stroke length. Obviously Tomei does it by using different length rods.

[T04GTR]

coool. running a 6:1 comp ratio will be great

[T04GTR]

diferand rod length and piston pin height for a longer throw crank. to keep the piston at the corect deck height.

running a shorter rod will only lower the compression ratio. by alot. if you really wanter to do it you would have to have a pistion with a pin height 2mm higher to compinsate for the shorter rod.

[T04GTR]

oh. 25/26 same rod. (in aftermarket)

[naklaju]

thanks for the reply guys...very good info here...