hey all... (have posted same question on sau also) trolled the forums last night for ages and come up with some useful info on casting numbers and what they mean etc My RB25 head, is cast 75T, so R33 RB25DET (9:1 comp) My block however, is cast 23U - 1997 Stagea AWD RB25DE (10:1 comp) Any ideas on what my compression ratio would be doing? i couldnt find any info on the turbo head on na bottom end anywhere (could be blind tho lol) MODS PLEASE MOVE IF YOU LIKE.... JUST REALISED I POSTED IN WRONG SECTION - SORRY