RB30DET compression

[88-SERIES200]

Hi i just need some proper advice on an engine im building. It is a genuine vl turbo bottom end with a rb25det head. could i run into any issues compression wise with using the standard turbo pistons with the twincam head and will this affect fuel enconomy?

[Pub247]

um you cant use stock turbo pistons with twin cam head i believe

There's no valve reliefs in piston for 4 valves

[88-SERIES200]

Thanks. Can anyone else validate this?? If using the stock turbo pistons is going to be an issue i might just use a single cam head until i can afford forgies with higher compression

[88-SERIES200]

also does anyone know if the vl turbo head uses stiffer valve springs than a non turbo head? I am aware that the cam is different.

[Pub247]

No springs are same but i suggest getting new ones theyre fairly cheap

Single cams make good power so not much point putting on twin cam unless your going all out

[88-SERIES200]

i already have the head with cams and exhaust manifold and dump pipe all i need is a plenum,sensors,dizzy,injectors etc. No i dont want big power just a quick and reliable street car. and i really like the note of the rb25 too and i thought that combination would make the power i want easily. 220 - 280 kw
Surely that wont cost much more than a rb30 single cam build

[nasty1]

220-280 rwkw good $5000-10000

[88-SERIES200]

I dont really see how.. maybe 5. I already have the block and head and other parts i need. I will be getting the block cleaned and honed and the head cleaned and checked but im keeping the stock rods just getting new pistons, rings, bearings. And that figure i gave is more a second stage of the build. I'd be happy with 170 - 200 straight up. what can the factory rb25 ecu and injectors handle?

[Pub247]

Your going to have to go forgies for the pistons to clearance the head They're an off the shelf item these days as its a common mod.

I assumed that you didnt have all the gear already which is why i said go single Cam.

You could probably keep the bottom end to 2000 including piston which are going to be half that cost

[cracker]

um you cant use stock turbo pistons with twin cam head i believe

There's no valve reliefs in piston for 4 valves

actually... they do.

use n/a bottem end, gives around 8.5 comp ratio.

turbo bottem end would be quite low...

[cracker]

i already have the head with cams and exhaust manifold and dump pipe all i need is a plenum,sensors,dizzy,injectors etc. No i dont want big power just a quick and reliable street car. and i really like the note of the rb25 too and i thought that combination would make the power i want easily. 220 - 280 kw
Surely that wont cost much more than a rb30 single cam build

gt35 standard manifolds, skyline injectors 440cc , single 044 or twin standard pumps and an after market ecu

piss it in.

[88-SERIES200]

Your going to have to go forgies for the pistons to clearance the head They're an off the shelf item these days as its a common mod.

I assumed that you didnt have all the gear already which is why i said go single Cam.

You could probably keep the bottom end to 2000 including piston which are going to be half that cost

Thats about the price i figured out. After paying a shop to do the machining then putting the bottom end together myself. (with alot of double checking and checking clearances etc) BUT i will need to get someone to weld up the vct on the head if i cant somehow adapt it to the 30 block.

[nasty1]

good luck.

youl spend $5000 in parts nearly........

then wiring aftermarket ecu
tunning it
then theres trans
diff

etc to worry about