[Andy Kain]

Over the winter months (continuing with the build on the car) I have started looking at forged internals. However I am a bit lost on the subject, I have found many different manufacturers and sizes (obviously for different RB engines).

I suspect that I will need 86.5mm pistons after having the block bored by .5mm, but this is just a guess, I have also found a set of 86mm standard size pistons, some have valve pockets on them others dont, any advice for the RB25DET R34 GTT Neo engine would be much appreciated?

Thanks

 

[RB26NL]

you could go 87mm, has been done many times.

 

[Andy Kain]

I have been reading good reports on CP pistons and 87mm is another choice for me. Lots more reseach to be done yet though.

 

[Sub Boy]

Always try to go for the smallest next size up, This way if the engine needs rebuilding again....There is room for the next size.

 

[GT-R Glenn]

What Chris said,
.5mm oversize which the same specs as factory one,
This is a 25 guys ...

 

[Chris Wilson]

Wiseco now list an RB26DETT forged piston in stock bore size, but sadly not yet for the RB25DET, for which they only list over size. If you build on a new factory block it's a bit of a pain, although some new blocks aren't bored that nicely....

 

[Autosaurus]

Hi Andy...The piston from an RB25 as fitted to the R33 GTS-T will not fit. The Neo motor has a different head with smaller combustion chambers. You can modify a R33 piston to fit but this can work out a costly excercise. I have seen in some product listings pistons to fit the RB25 as fitted to the R33 and R34 Skyline, when I called said suppliers they didn't even know that it was a different head in the 34 and as such they wouldn't work...
The Neo pistons have valve pockets in whereas the older RB25 pistons don't... The Neo has GTR conrods fitted as standard, these are good for up to 600 bhp...
Last time I needed some I got 2 sets of custom pistons made by Wossner, I got 2 sets as it was only slightly more expensive than 1 set, I have none left now. AFAIK no one lists an off the shelf forged piston for the Neo engine... I know Chris from Conceptua tuning got some custom made a month or 2 back, worth giving him a call on 0800 0234423...