Pistons for RB25 / 30 head conversions, you can now buy them

[slimvl]

check out the 100+ page thread on sau they have all the info your after

[spandex]

Originally Posted by 650hp

I will be using the Arias pistons but will be aiming for around 9:1 comp.

So machining will required.

PS: Arias are $1200 from modyourcar

Arais Rb30/25 pistons $1130 Click me

[vhr32]

CP

All compression ratios are based on zero deck height
1.2mm head gasket (7.13cc)
RB25 @ 62.5cc
RB26 @ 64.5cc
They assure me they have done alot of work to make sure the facts are correct.

p/n= CP-RB30/26-.20
Flat top with no valve pockets
8.2:1 COMPRESSION RATIO with RB25 head and bit less with RB26 head
21mm pin
1.280" compression height
Only stocked in 0.20 thou oversize but can be custom ordered in any size.

p/n= CP-RB30/26-.20-9.0
6.0cc dome top,
9.0:1 COMPRESSION RATIO with RB25 head and bit less with RB26 head
21mm pin
1.280" compression height
Only stocked in 0.20 thou oversize but can be custom ordered in any size.
*Care must be taken when using on RB26 with more than 11.5mm valve lift*


ARIAS

Suit RB30/26
p/n= AP332103
flat top
21mm pin
1.280" compression height
Only stocked in 0.20 thou oversize (86.5mm).
COMPRESSION RATIO 8.4-8.6

Suit RB30/26
p/n= AP332104
10.6cc dome top
21mm pin
1.280" compression height
Only stocked in 0.20 thou oversize (86.5mm).
COMPRESSION RATIO 9.2-9.4

Suit RB30/25
p/n= AP332105
13cc dome top
21mm pin
1.280" compression height
Only stocked in 0.20 thou oversize (86.5mm).
COMPRESSION RATIO 9.5-9.8


WISECO

Skyline RB30 w/ DOHC RB25det cylinder head
1.260" compresion height, 66.5cc head chamber, Dish top -11.3cc, 7.0:1 compression ratio, 21mm pin, 1mm gasket thickness, 1mm deck clearance.

K577M865 86.5mm
K577M87 87.00mm


ACL

6MKRY9608 (VL turbo)
87mm, -4.5cc dished top, 1.261" compression height, 21mm pin,

Standard RB30ET pistons are 7.8:1, with RB25 head it is 7.1:1 but these ACL pistons are bumped up to 8.5:1 with SOHC head,
so with the RB25 head it may give about 7.5:1??

[7FOUR7]

so if i buy cp 9.1 ratio forgies, will it drop to the ideal ratio once the 26 head goes on? also do i have to use the oil squirters?

[Careless]

hello all.

First post =) (had to register, been trolling the boards for too long now)

can we add some high performance N/A applications here?

I'm looking at getting VG30DE Pistons from JE Pistons coupled with Spool Rods. They make a 10.5:1 compression piston which should fit spool rods quite nicely. they come in 87.5, so an overbore is required (the block needs it anyways).

does anyone know if the valve reliefs on the pistons are gonna be an issue, or Are they most likely the same degree/angle? I've been advised by a reputable RB30 builder on this, but I'd like some added assurance, because these parts aren't cheap.

RB26 R33 head is going on there too.

EDIT: After cubes and I conversed, and after I doubled his calculations, we arrived at 9.11 to 1 with VG30DE pistons and some decking here and there. Add to the fact that I've come to realize these 87.5 mm head gaskets are harder to come by, it sorta makes it hard to justify going with the VG30DE pistons. I think I should probably get some custom CP Pistons made or something. I know this is a black-magic type art in picking pistons, but what's everyones general opinion about pistons?

Ideally I'm looking for 10.5 but I'll settle for 10.1 compression ratio.

Are there any 87 or 87.5 mm forged pistons for RB's that can achieve that with an RB26 head, or will i have to customize them? Even a bit more than 10.5 is cool.

EDIT:

what's the chance of me getting arias to make these in 87 mm?

Suit RB30/26
p/n= AP332104
10.6cc dome top
21mm pin
1.280" compression height
Only stocked in 0.20 thou oversize (86.5mm).
COMPRESSION RATIO 9.2-9.4

assurance, because these parts aren't cheap.

RB26 R33 head is going on there too.

EDIT: After cubes and I conversed, and after I doubled his calculations, we arrived at 9.11 to 1 with VG30DE pistons and some decking here and there. Add to the fact that I've come to realize these 87.5 mm head gaskets are harder to come by, it sorta makes it hard to justify going with the VG30DE pistons. I think I should probably get some custom CP Pistons made or something. I know this is a black-magic type art in picking pistons, but what's everyones general opinion about pistons?

Ideally I'm looking for 10.5 but I'll settle for 10.1 compression ratio.

Are there any 87 or 87.5 mm forged pistons for RB's that can achieve that with an RB26 head, or will i have to customize them? Even a bit more than 10.5 is cool.

EDIT:

what's the chance of me getting arias to make these in 87 mm?

Suit RB30/26
p/n= AP332104
10.6cc dome top
21mm pin
1.280" compression height
Only stocked in 0.20 thou oversize (86.5mm).
COMPRESSION RATIO 9.2-9.4


EDIT 2:

hmmm. seems that even these won't give me anything over 9.4 with a 0.040 quench and a 1.2 mm HG.

any help out there?

[Careless]

well i emailed arias, and they aren't being very helpful. the only bit i got out of them was "the pistons will have to be custom, 155 dollars per piston".

i asked that they forward my email to someone with some technical background with rb30/26 (because the given combustion chamber volume of 64.5cc in this thread was apparently the result of a lot of research), and yet, no reply.

help anyone?

arias was quite useless.
i contacted them regarding what needs to be done to achieve my desired CR, and they told me that i need custom pistons for 155 a pop. No tech specs, nothing. haven't heard from them regarding the interference issues with 9.15 lift or how much i have to deck off the head... NOTHING.

can anyone help me?

[twinvl]

Another option for you is to use RB25DE pistons, and if u must have 87mm i'm sure u can get them oversized.
I cant remember what the comp is with them, i think somewhere around where u want (10.5+)! Could be cheaper too, u don't need forgies for na, even with high comp, u just need a good tune.

[terryo]

I'll be happy to help technically. where I work, we do RB performance engine building jobs all the time and we have some data on the various piston/head/cam combos that work, both turbo and NA. We have been selling/using Mahle motorsport pistons for RB turbos engines recently. Truly beautiful things and much better quality than some others on the market, and for similar prices. Various of their pistons come with coated piston skirts. PM me if you want specific engine help, or just post here any general engine queries and I'll answer them if I can

[rodger1]

Originally Posted by darkstar

1500 to 1800 is a good price for forgies, depending on what you get for it.

Friend recently got some rb25 pistons, standard forgies for 1500, might be SPS ones im not sure.

Truly an art work, i think that was wtih rings and gudgons, but they were albit incomplete.... needed to cross drill the gudgion pin housing for an oil squirter, but oitherwise great.

i got my aries forgies for $1100.00 at trade price from rocket including pins retainers and rings, the rb30-25 head conversion pistons have been avaliable from aries for like over a year and a half when i bought my pistons they were avaliable p.s machining piston crown is not a good idea it destroys your warranty on the pistons because it weakens the crown and brings the top ring closer to the combustion. why not buy the right **** first and stop messing around have a look at rocket http://rocketindustries.com.au/search.php?keyword=rb30 they only have them for 86.5mm bore but i think if you ring them up they probally have them in stock

[Cubes]

I've now managed 80,000km's on a set of 87mm RB25 Wiseco pistons with the std ring pack in the rb30det.

Still appears to be running well and not using oil; of which has surprised me considering they have always slapped a little first thing in the morning.

The RB25 wiseco pistons are not ideal as they sit slightly down the bore. I've had mine decked 0.040"; from memory they still sit down the bore ~0.020".

Pitty wiseco don't make something more suitable for the rb30det combination.