First off they are two completely different blocks.
Second the bore is the same yes but as you have just said the stroke between the two is different you got that part right.
The craddles are completely different and not interchangeable. The dimension are different and so is the strength. You can not mount the gearbox out of a GTS4 or a GTR to the block of a GTS25t, while the R33 GTS4 block you can funny that.
so what does that tell you? the blocks are different in not only the back of the block but in the size and strengths of them. The R32 GTS4 block is different that of the R32 GTS-t block. The are heavier and much stronger. You don't get the flex out of them as you do in the 2wd blocks.
Now you mention 20psi on factory internals. Ok for how long? A steady diet of that and you WILL crush the ring lands. How do I know this? Well lets see. (4) R33 GTS25-t's have had that done already, and (3) GTR's already that I know of personally. I know the owners and I know the cars. They were tuned and other bits put on properly yet the same thing happended on all 7 motors.
Now you mention the RB30. Well that was used in the R30 and R31 skylines, and the VL comodore. They were single over head cam motors. The major difference there is the mounting for the trans has the same pattern as the GTR and GTS4. how do Iknow this? A tuning house by the name of Advanced Imports did a 3 litre conversion on an R32 GTS4 some years back. They put an RB25DET head on it. It was a nightmare from hell to do and as I read the article and talked to Peter Hopkins about it he says and I quote " never again. From the begining it posed many problems getting it to work right".
Another notable is the fact once you stroke the RB26 block to 2.7 or 2.8 litres #3 cylinder has a tendancy to crack. Again how would I know this? Well Crodyon Wholesalers R32 GTR has went through 3 count them 3 N1 blocks with the same failure. Reece Megreggor, current holder of the quickes 4wd car in Australasia has had it happen as well and his is not even stroked.
If the R25 block was so strong then why don't the Japanese use them instead of the more expensive or should I say much more expensive RB26 block? In the JGTC all he Skylines are 2wd and up until recently all used the RB26 block. They did not use the RB30 or RB25 blocks, and that was for a very good reason. Reliability and strength.
I am not taking anything away from the RB25 block as yes it can produce some good hp numbers. In fact I have heard of a few in Japan pushing 900hp, but they don't last long even with the right gear in them.
People need to get it out of their heads that all the RB blocks are the same in strength and durability. If they were Nissan would have not made the RB26 block as a seperate casting as they did. The would have merely incorparated the other blocks to fit as needed.
You don't have to beleive me. Contact these following companies and ask them for youself.
Lee Sutton @ Advanced Imports
http://www.advan.co.nz/
Nick Jenkins or Greame McDonnald @ Croydon Wholesalers
http://www.croydons.co.nz/
Sub Zero In Australia
http://www.sub-zero.com.au/
Rob Bryan @ Possum Bourne
http://www.possumbourne.co.nz/index.html
Now I have provided you with the means to get proper information. Please do so as you will learn a lot
