Hi all, Im planning on putting a RB25 head onto the 30 block in the near future. I will also be converting to manual, so a R33 box could come in handy. I was wondering, if I bought a half cut, are the parts from the RB25 bottom end able to be used in the RB30 bottom end (I have read that the 25 pistons will work, and rods??), but just getting into a bit more nitty gritty how will they work with compression etc? ? Or on the other had, would I be better off purchasing the head and the box seperate and just leave the VLT bottom end stock? (also I have read that the crankshaft in the RB30 has issues up around 7000RPM, im guessing the 25 crankshaft cant replace it but??) Thanks guys, Josh Some original photos have not been recovered yet.

buy a halfcut, that way u get wiring, ECU, box, brakes and other goodies, sell the front panels if they're any good, front suspension if its got decent coilovers in it, dash parts etc

The rb25det pistons run a different comp height (they sit lower in the bore) so it will work but definitely not optimal. Just sell the 25t bottom end as they always break ring lands. Some P plater will buy it when they decide its cool to shove 14psi in to it without a tune. All though you can find this info out by searching simply grab an N/A RB30E bottom end and drop the rb25 head on to it (with the vct oil mods). That will grab a nice 8.2-8.3:1 comp ratio perfect for turbo. Unless your running a nice exhaust manifold and plenum you won't be reving past 7000rpm anyway so the rb30 high rev issues isn't a problem. If you do - then a full length crank collar, forged rods, pistons and an ATI balancer, vent the sump to atmo, 1.2-1.5mm oil restrictors depending on the oil pump you use and that will see it to 8500rpm without problems providing the build is good. BUT 8k really needs a turbo around the size of a GT40+. 7.5k for the GT35 and 7-7.5k for the GT30.